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Cribellar threads are primitive prey capture threads formed of thousands of fine, looped cribellar fibrils that surround larger, supporting fibers. Cribellar fibrils are produced from the spigots of an abdominal spinning field, the cribellum, which may be either a single, oval plate or a pair of medially divided plates. The number of spigots on a spider's cribellum is known to be directly related to the stickiness of its cribellar thread. Some spiders deposit cribellar threads in their webs as taut, self-supporting linear threads; others deposit looped threads along a supporting foundation thread. This study showed that the looped cribellar threads of Kukulcania hibernalis (Filistatidae) and Mexitlia trivittata (Dictynidae) were wider and stickier than linear threads produced by Waitkera waitakerensis and Uloborus glomosus (Uloboridae), respectively, that had the same numbers of cribellum spigots. Linear cribellar thread spun from the divided cribellum of K. hibernalis was both wider and stickier than linear thread spun from the undivided cribellum of W. waitakerensis that had the same number of spigots. A single cribellar plate of K. hibernalis and the cribellum of Siratoba referena (Uloboridae) had a similar number of spigots and produced cribellar threads with similar stickiness. Thus, both a spider's spinning anatomy and its spinning behavior affect the stickiness of its cribellar threads.

Because the morphology of the cuticular scales of spiders is extremely variable both within and between families,anny study attempting to use cuticular scales as a systematic character must first have a formal definition that differentiates scales from other types of setae. The purpose of our study was to evaluate the characters used previously in the literature to distinguish cuticular scales from other types of setae and, if necessary, to provide a new, comprehensive definition for this setal type in spiders. The results of our SEM survey of the surface morphology of the scales of 23 species of spiders representing 10 families do not support the morphology of the socket as a reliable character for distinguishing scales from other types of setae. Our results indicate that cuticular scales should be defined as flattened setae that have a pedicel bent so that the scale overlays the surface of the cuticle. Our results also suggest that the urticating hairs of theraphosid spiders should not be considered to be a type of cuticular scale. Instead, we propose the recognition of three main types of scales: lanceolate, spatulate, and plumose. In addition to qualitative comparisons, we measured and compared the cuticular scales for several species and found that differences in scale width were directly related to the morphotype of the scales being examined. Additional key words: Araneae, morphology, SEM, macrosetae, urticating hairs Of the 105 currently recognized families of spiders (Coddington & Levi 1991), 13 families have at least one species that possesses cuticular scales (Kaston 1978; Roth 1993; Townsend, unpubl. data). These families are the Anyphaenidae, Araneidae, Corinnidae, Gnaphosidae, Heteropodidae, Liocranidae, Lycosidae, Oxyopidae, Philodromidae, Pisauridae, Salticidae, Thomisidae, and Uloboridae. Thus far, the microanatomy of the cuticular scales of spiders has been described adequately only for the Salticidae (Galiano 1975; Wanless 1978a, b; Hill 1979; Cutler 1981, 1987; Cutler & Jennings 1985; Felgenhauer 1998) and the Oxyopidae (Lehtinen 1975; Townsend & Felgenhauer 1998a). In these spiders, cuticular scales exhibit a tremendous diversity of colors, distributional patterns, and morphology. In certain species, scale morphology, distributions, and colors have even been observed to vary ontogenetically (Crane 1948; Townsend & Felgenhauer 1998a, b) and sexually (Kaston 1978; Hill 1979; Townsend & Felgenhauer 1998a). At least two definitions for the cuticular scales of spiders exist in the published literature (Hill 1979; Roth 1993). According to Roth (1993), cuticular scales a Author for correspondence. E-mail: vrt5719@usl.edu are flattened setae that lack innervation and have a highly reduced socket morphology; Roth (1993) also recognized the three major morphotypes of the scales of spiders as being lanceolate, spatulate, and lamelliform. In his definition, Roth (1993) considered the urticating hairs of theraphosid spiders (i.e., tarantulas) to be a type of cuticular scale. Urticating hairs are setae that lack innervation, occur in four distinct morphotypes (Types I-IV), and typically exhibit a localized distribution, i.e., a single dense patch of hairs on the dorsal surface of the opisthosoma (Cooke et al. 1972). In contrast to Roth's definition, Hill (1979) defined a cuticular scale as being a modified, flattened seta composed of fused cuticular elements that has a pedicel bent at an obtuse angle so that the scale overlays the surface of the cuticle. In his discussion of cuticular scales in spiders, Hill (1979) made no reference to socket morphology, innervation, or homologies with the urticating hairs of tarantulas. Terminology used to describe the specific features of the surface morphology of cuticular scales of spiders was adopted by Hill (1979) from the terminology used to describe the surface features of the cuticular scales of lepidopteran insects (Downey & Allyn 1975). For instance, the proximal tip of the scale that inserts into the socket is known as the pedicel (Fig. 1). In This content downloaded from 157.55.39.163 on Wed, 21 Sep 2016 05:58:03 UTC All use subject to http://about.jstor.org/terms Cuticular scales of spiders ~~~~~~oMPw11wb-;O"a _16 *--# Figs. 1-4. SEM micrographs of the major surface features of the cuticular scales of spiders. Fig. 1. The dorsal surface of the opisthosoma of the salticid spider, Phidippus audax. Note the bent pedicel (p) of a scale. Scale bar, 30 pm. Fig. 2. Inferior surface of the cuticular scales from the prosoma of the salticid spider, Hentzia mitrata. Inferior spine (is). Scale bar, 10 pm. Fig. 3. The dorsal surface of the prosoma of the oxyopid spider, Oxyopes salticus. Note plicae (pl) occurring on the superior surface of a scale. Scale bar, 15 wLm. Fig. 4. The prosoma of the anyphaenid spider, Aysha velox. Note setule (sl) originating from the lateral surface of a scale. Scale bar, 20 lim. jumping spiders, the pedicel is bent so that an -135? angle is formed between the pedicel and the blade of the scale (Hill 1979). Small projections occurring on the lateral, inferior, and superior surfaces, as well as at or near the tip, are termed spines and are named on the basis of their location. For example, projections occurring near the tip are known as apical spines, whereas those occurring on the inferior surface are known as inferior spines (Fig. 2). Ridges, in turn, that are arranged in a longitudinal orientation along the long axis of the scale are called shafts, whereas smaller, lateral ridges are termed plicae (Fig. 3). Small lines or depressions on the superior or inferior surfaces are known as striae, while long, relatively thin processes that arise from the lateral surfaces are called setules (Fig. 4). In contrast to the paucity of research devoted to the cuticular scales of spiders, the morphology and ultrastructure of the scales of lepidopteran insects have been examined in many studies (Snodgrass 1935; Overton 1966; Chapman 1969; Greenstein 1972; Ghiradella 1974, 1984, 1985, 1989, 1994; Nijhout 1980). In these insects, cuticular scales have been observed to serve multiple functions (Scoble 1995) including defense (Robinson et al. 1969), thermoregulation (Chapman 1969), and communication (Birch et al. 1990). In spiders, scales have been hypothesized to function in similar capacities (Simon 1901-1903; Hill 1979; Cutler 1987), but no empirical research has been published that has experimentally tested any of these proposed functions. The general purpose of our study was to examine and evaluate the morphological characteristics of cuticular scales that were proposed originally by Hill (1979) and Roth (1993) and, by doing so, provide a comprehensive definition for cuticular scales in spiders. In addition, through a comparison of the surface morphology of cuticular scales and urticating hairs, we sought to clarify the relationship between these two distinct types of setae. To accomplish these tasks, a 319

1. Cribellar thread is the most primitive type of capture thread found in the aerial webs spun by spiders and is composed of thousands of dry, looped fibrils that are spun from the spigots of a spinning plate. 2. Comparison of the strength with which cribellar threads produced by two species of spiders in the family Uloboridae held five insect surfaces demonstrates that the size, type and density of insect setae influence a thread's stickiness. 3. Moth wings were held the least strongly, as their detachable scales easily pulled free of the wing and remained attached to the cribellar threads. 4. Two forces were responsible for holding the other insect surfaces: setal snagging caused the stout setae of a fly notum to catch on the fine fibrils of the cribellar thread, whereas an uncharacterized force held the smooth surface of a beetle elytra and the setose surfaces of a bug hemelytra and a fly wing

The prey capture threads of a spider's orb-web retain insects that strike the web until the spider can subdue them. To determine how changes in web architecture influence thread effectiveness, the stickiness of cribellar prey capture threads produced by nine species of similarly sized spiders from the family Uloboridae was measured. The weight-specific stickiness of these threads differed by as much as 5-7-fold among the species and was correlated with differences in web architecture. Threads spun by representatives of five orb-weaving genera were less sticky than those spun by species that make reduced webs. Two species of the simple-web genus Miagrammopes produced stickier threads than two species of the triangle-web genus Hyptiotes

Spider species (Araneae) inhabiting citrus ecosystems have been collected and identified in Florida (Muma 1975, Mansour et al. 1982) and California (Carroll 1980), but there is no comparable information from Texas. The seasonal abundance of selected arthropod predators was studied by Fuchs & Harding (1976) in southern Texas, and spiders were identified only to order. Except for ant species regarded as potential pests of citrus (Schuster & Dean 1957, Dean et al. 1983), the identity of ant species occurring in citrus ecosystems remains largely obscure. Spiders and ants were collected from southern Texas citrus ecosystems from August 1990 to March 1991 (a total of 12 sampling dates) over a wide area of Hidalgo and Cameron counties by using hand collection, an aspirator and sweep net. Species were gathered from citrus leaves, branches, trunks and from the ground surrounding the trees on a qualitative basis; no quantitative collection methods were used. With the addition of three spider species collected from citrus trees by one of the authors in 1983 (D.A.D.), and two species of ants listed in Dean et al. (1983), a total of thirty three species of spiders from 13 families and twelve species of ants were identified (Table 1). Comparing spider species using only relative frequency of discovery, 36% of the total number of spiders collected were orb weavers of the family Araneidae, with 63% of these belonging to the species Metazygia zilloides (Banks). The next most numerous family was comb-footed spiders (Theridiidae, 12%), followed by crab spiders (Thomisidae, 11%), jumping spiders (Salticidae, 11%), wolf spiders (Lycosidae, 9%), long-jawed orb weavers (Tetragnathidae, 4.5%), ground spiders (Gnaphosidae, 4.5%), horizontal orb weavers, sac spiders and ghost spiders (Uloboridae, Clubionidae and Anyphaenidae, respectively, all with 3%), mesh web weavers, pirate spiders and lynx spiders (Dictynidae, Mimetidae and Oxyopidae, respectively, all with 1%). Relative numbers of ant individuals were not compared, but the tropical fire ant, Solenopsis geminata (Fabr.) was observed in citrus groves more recurrently than any other. The tropical fire ant, although a predator of insect pest species of other crops, is considered a potential pest of citrus by Dean et al. (1983). Solenopsis geminata is capable of occasionally girdling citrus trees, may often tend honeydew excreting insect pests like aphids, mealybugs and brown soft scale (which may interfere with their parasitoids and predators), and can attack pickers and other field workers (Dean et al. 1983). Most of the other ants, except Atta texana and Pogonomyrmex barbatus, also tend aphids. There have been few studies of spider predation in citrus groves and most of these used a mixture of field and laboratory observations. Mansour & Whitcomb (1986) found spiders, largely the sac spider Cheiracanthium mildei L. Koch, to be important controlling factors of the barnacle scale, Ceroplastes floridensis Mask (Homoptera: Coccidae) in citrus groves in Israel. Carroll (1980) suggested that sac spiders were the most important spiders in terms of control on citrus arthropod pests, and Cherrv & Dowell

Episinus spiniger (O.P.-CAMBRIDGE) is recorded for the first time from Taiwan. Three new species of the genus Episinus, E. yoshimurai, E. punctisparsus and E. bicornutus, are described from Taiwan and Japan.

Stabilimenta consist of straight or zigzag bands of ribbon silk which are arranged in species and age-specific patterns within the free zone and sometimes the hub ofthewebs ofmany diurnally active orbweaving spiders, including members of both major families of orbweavers (Araneidae, Uloboridae). The relativelycommon occurrence of stabilimenta among the orb-weaving guild suggests that they have one or more important functions. Although a number of functions have been suggested (see Robinson and Robinson, 1970, 1973), the actual significance of any of these proposed functions has not yet been demonstrated (Levi, 1978). I present here experimental evidence which suggests that the stabilimenta ofArgiope aurantia Lucas and A. trifasciata (Forskal) aid in defense against avian predators. The stabilimenta of all but the early instars of A. aurantia and A. trifasciata are vertical zigzags of silk located above and or below the hub, where the spider rests. Early instars ofA. aurantia, as well as the early intars of several other Argiope spp. produce a disc stabilimentum. The vertical stabilimentum is also constructed by other Argiope sp. (e.g.A. bruennichL A. lobata). Some Argiope spp. produce a cross stabilimentum composed of zigzags of ribbon silk arranged in the pattern of an "X" around the hub (e.g.A. argentata, A. florida, A. pulchella, A. savignyi). All Argiope spp. produce some form of stabilimentum (Levi, 1968). Argiope spp. reside during daylight hours at the hub of the web, a position which exposes them to potential predators. This exposure to potential predators suggests a defensive function for stabilimenta. Defensive functions for the stabilimenta ofArgiope spp. have been suggested by various authors (Hingston, 1927; Marson, 1947; Lubin

The six Japanese species of the genus Uloborus are transferred to the other genera related to Uloborus: sinensis SIMON, varians BOSENBERG et STRAND, incognitus DONITZ et STRAND, yesoensis (SAITO) and sybotides BOSENBERG et STRAND to Octonoba; prominens BOSENBERG et STRAND to Philoponella. Uloborus tokyoensis KISHIDA is synonymized with Octonoba sinensis (SIMON). A key to the genera of the subfamily Uloborinae is given.

Differences in web structure and cephalothorax features suggest that Hyptiotes cavatus should exert more force while monitoring its vertical triangle-web than Uloborus glomosus exerts while hanging beneath the hub of its horizontal orb-web. When this hypothesis was tested by measuring the force that instars of each species exerted on a horizontal thread, Hyptiotes cavatus was found to exert significantly more force throughout development than did Uloborus glomosus. This relationship holds when either first femur length or body weight is used as an index of spider size.

In an unsprayed cotton field in east Texas, orb weavers were one of the numerically dominant groups of spiders, constituting 10% of all spiders collected by D-vac during the summer of 1985 (range, 0.04 individuals/m2 in June to 0.72 individuals/m2 in August). Direct counts, conducted during peak orb-weaver density in August, showed that 0.86 individuals/m2 were found. More than two-thirds of all orb weavers collected by D-vac in cotton consisted of the five species Acanthepeira stellata (Walckenaer), Neoscona arabesca (Walckenaer), Gea heptagon (Hentz), Tetragnatha laboriosa Hentz, and Uloborus glomosus (Walckenaer). Their prey consisted of insects (>99%) and spiders 90% of the prey of the orbweaving spiders, which are characterized as generalist predators. Differences among the five spider species indicate that prey selection was occurring; this seems to be determined by web location, web inclination, and web strength. Of the orb weavers occurring in cotton, 99% were small-sized spiders (primarily G. heptagon ) that intercept small prey with their delicate (about 4 cm diameter) webs. These orb weavers are predators primarily of smallsized pests such as the cotton aphid, Aphis gossypii Glover, and the cotton fleahopper, Pseudatomoscelis seriatus (Reuter).

The spinning apparatus of the uloborid spider Polenecia producta was studied to complete previous studies on the same family of spiders. The structure of spinnerets and spigots, under scanning electron microscopy, and the main anatomical and histochemical characteristics of the spinning glands of adult females and males are described. In addition some observations on the spinning apparatus at three successive stages of development are made. There are nine kinds of silk glands in Polenecia, i.e. one more (aciniform — B glands) than found in other uloborids. The spinning apparatus of Polenecia is, therefore, the most complex so far known. It is also more complex than that presently known of Araneoidea. The characteristics of the spinning glands of Polenecia are compared with those of other uloborids. Present knowledge of the spinning apparatus of uloborids leads to a renewed discussion of the origin of the orb web in this family and in araneids. It is concluded that these two types of orb webs emerged from independent evolutionary processes.

Uloborids that spin reduced webs more actively monitor them than those that construct orb webs. Hyptiotes use both their first and fourth legs to tense their triangle-webs, whereas Miagrammopes rely principally on their first legs to monitor and jerk the threads of their irregular webs. The respiratory systems of these spiders include tracheae that extend into the prosoma, bifurcate, and enter the legs. To determine if the legs responsible for active web-monitoring tactics have more extensive tracheal supplies, the total cross sectional area has been computed of the tracheae entering the legs of mature female orb web and reduced web uloborids. Each leg's value has been divided by the cross sectional area of the tracheal trunks that enter the prosoma. These indexes reveal no significant differences between the relative tracheal supplies of the orb weavers investigated (Waitkera waitkerensis, Tangaroa beattyi, Uloborus glomosus). But the first, third, and fourth legs of H. cavatus and the first legs of M. animotus and M. pinopus have greater relative tracheal supplies than those of the three orb weaving species. Relative to leg volume, the first and fourth legs of H. cavatus have the greatest and the first legs of Miagrammopes species the next greatest tracheal supplies. When tracheal lengths are considered, these differences in potential oxygen supplies remain, showing that area differences do not simply compensate for differences in the distances over which oxygen must diffuse. These differences are leg-specific and not species-specific, and uloborids with the most extensive tracheal supplies are found in moist habitats. Thus the observed differences are best explained as adaptations to meet the greater oxygen demands of legs responsible for active web-monitoring tactics and not as adaptations to reduce respiratory water loss.

Philoponella oweni (Uloboridae) is a facultatively communal spider found in the southwestern United States. Solitary females and communal groups of females coexist in the same habitats. Communal females are known to produce more eggs than solitary females. Communal females might acquire the energy for the production of additional eggs by one of three means: they might have a longer life span, and thus more time in which to acquire energy; web maintenance might be more efficient in a communal group; or communal females might spend more time feeding. Field data from a marked population in Arizona showed the third alternative was true.

Uloborid cribellar silk consists of torus-shaped puffs. In Miagrammopes animotus the width of these puffs is about 36% that of the cribellum of the spider and shows a 2.3-fold increase in surface area during development. The cribellar spigot number increase 5.7-fold during development, although, relative to spider mass, it decreases by 34%. Cribellum width is the best predictor of both cribellar silk puff width and length and is as good a predictor of puff surface area as is cribellum surface area. Relative to cribellum width, the length of the calamistrum comb responsible for drawing fibrils from the cribellum changes little during development. The attachment points of cribellar silk to a parallel frame thread become more widely spaced during development, although the number of puffs they delimit changes little.

Besides the two axial fibers and the mass of cribellum fibrils, a third component is present in the capture threads of uloborids. This is a substructure originating from the paracribellum. It probably helps to fasten the axial fibers in their position. The axial fibers are secreted from the two glandulae pseudoflagelliformes whose spigots are situated on the posterior spinnerets. It is hypothesized that the cribellum fibrils become jammed and thus fixed between the axial fibers by periodical abduction and adduction of these spinnerets.

Colonial spiders have individual capture webs (territories) within a communally shared web structure. I describe here the life histories and colony population dynamics of two communal species, Ctrtophora moluccensis (Doleschall) (Araneidae) in Papua New Guinea and Philoponella republicana (Simon) (Uloboridae) in the Panama Canal Zone. In both species, dispersal and foundation of new colonies are primarily by groups of immatures. Population growth of new-colonies was rapid during the first generation, but then colony population size decreased markedly. Colonies of P. republicana rarely lasted more than one generation, whereas those of C. moluccensis attained an equilibrium population size and often persisted for many generations at the same site. Reproduction occurred during the wet season in P. republicana colonies and year-round in colonies of C. moluccensis. Reproduction was synchronized in widely separated colonies of P. republicana. Factors controlling population growth and survival of colonies are discussed. Cyrtophora moluccensis colonies were probably regulated by density dependant factors, especially predation and parasitism, and perhaps a shortage of flying insects due to colony visibility. Philoponella republicana colonies were most likely limited by climatic conditions and instability of the habitat (i.e. density independent factors). Colonial social organization influences both dispersal and colony population growth. Coloniality is, however, compatible with various life history strategies.

In the family Uloboridae, web reduction is associated with changes in web monitoring posture and prosomal features. A spider must extend its first pair of legs directly forward to monitor the signal line of a reduced web. This posture is facilitated by shifts in prosomal musculature that cause reduced web uloborids to have a narrower anterior prosoma, a reduced or absent anterior eye row, and prominent posterior lateral eye tubercles. The eye tubercles and larger posterior eyes of these uloborids suggest that web reduction may also be accompanied by ocular changes that compensate for reduction of the anterior eyes by expanding the visual fields of the posterior eyes. A comparison of the visual fields of the eight-eyed, orb web species Octonoba octonaria and a four-eyed, reduced web Miagrammopes species was made to determine if this is true. Physical and optical measurements determined the visual angles of each species' eyes and the pattern of each species' visual surveillance. Despite loss of the anterior four eyes, the Miagrammopes species has a visual coverage similar to that of O. octonaria. This is due to (1) an increase in the visual field of each of the four remaining Miagrammopes eyes, accruing from an extension of the retina and an increase in the lens' rear radius of curvature, and (2) a ventral shift of each visual axis, associated with the development of an eye tubercle and an asymmetrical expansion of the retina. Miagrammopes monitor their simple webs from twigs or moss where they are vulnerable to predation. Therefore, maintenance of visual cover may enable them to detect predators in time to assume or maintain their characteristic, cryptic posture. It may also allow them to observe approaching prey and permit them to adjust web tension or prepare to jerk their webs when prey strikes.

On the Collections of Spiders (Arachnida, Araneae) Made by the Mongolian-German Biological Expeditions of 1977 to 1979 30 species of spiders collected during the Mongolian-German Biological Expeditions of 1977 to 1979, are recorded. Some zoogeographical remarks are given. Possibilities how spiders can exist under semi-desert conditions of Mongolia are discussed.

Members of the genera Uloborus, Hyptiotes, and Miagrammopes have similar web-monitoring postures, but very different webs and tactics for monitoring them. Orb weavers of the genus Uloborus construct horizontal webs and hang from their hubs, whereas reduced-web uloborids construct vertical webs and monitor them from a single thread. To determine if changes in spider strength accompanied web reduction, resting and maximum force measurements were taken of a developmental series of Hyptiotes cavatus, Uloborus glomosus, Miagrammopes animotus, Miagrammopes pinopus, and an undescribed Costa Rican Miagrammopes using a glass needle strain gauge. Both carapace length and spider weight were used as indexes of spider size. Regression analyses of forces show that H. cavatus exerts the greatest relative force and Miagrammopes species the least. This is consistent with requirements for the operation of each web type: Hyptiotes cavatus tenses its entire triangular web and suddenly releases this tension when a prey strikes its web, whereas a Miagrammopes species jerks a single thread that has captured a prey. Within the genus Miagrammopes, the species with the most highly modified carapace expressed the greatest resting force.

Seven new species of the genus Octonoba are described from the Ryukyus. These species inhabit only a few islands in the limited extent, and their distributions are not overlapping one another.

When visual fields of the primitive orb-weaver, Waitkera waitkerensis, are reconstructed using measurements taken from intact lenses and cross and longitudinal sections of the prosoma, they show that this species has complete visual surveillance, but that none of the visual fields of its eight eyes overlap. The more advanced orb-weaver, Uloborus glomosus, also has eight eyes, but each eye has a greater visual angle, giving this species a complex pattern of overlapping visual fields. Uloborids that spin reduced webs are characterized by reduction or loss of the four anterior eyes and other carapace modifications necessary for them to effectively monitor and manipulate their reduced webs. The eyes of these uloborids have greater visual angles than those of orb-weavers, resulting primarily from perimetric expansion of their retinal hemispheres. Additionally, the axes of their visual fields are more ventrally directed due to greater dorsal than ventral retinal expansion and to ventral redirection of the entire eye. Consequently, even though the anterior lateral eyes of the triangle-weaver Hyptiotes cavatus lack retinae, the species' six functional eyes permit complete visual surveillance and exhibit visual overlap. The single-line-weaver, Miagrammopes animotus, has lost its four anterior eyes, and with them much of the anterior vision and all of the visual overlap found in the other species. However, changes similar to those of H. cavatus permit this species to retain most if its dorsal and ventral visual surveillance. Thus, ocular changes act in consort to maintain relatively complete visual surveillance in the face of eye loss and other major carapace modifications necessary for the operation of reduced webs.

The distribution ofUloborus diversus webs around pack rat nests on the desert near Cave Creek, Arizona, differences between webs there and in nearby residential Phoenix, and differences between the webs of large and small individuals indicate that these spiders select web sites and designs to minimize web damage by wind. The frequency of web construction decreased when spiders in captivity were exposed to wind or to relatively bright (5 Lamberts) nights. Observations of web sites on the desert revealed high rates of web-turnover and substantial frequencies of movements of spiders from one site to another. Much lower rates of web-turnover and spider movement occurred in less windy situations in the laboratory, and in suburban Phoenix. Partial web replacement and the extension of web construction over two nights are apparently methods used to improve catching ability of sheltered (longer lived) webs by extending their surface and/or tightening their mesh.

Synopsis. Araneomorph spiders from many different families show some regional differentiation of the duct which carries the drag-line silk, but only in the orb-web spiders is there a well-defined control valve. This valve, and its associated muscles, is described for Araneus diadematus (Argiopidae), an ecribellate spider, and is compared with that found in Uloborus octonarius (Uloboridae), a cribellate spider. It is suggested that the remarkable similarity between the valves in these two groups implies evolutionary convergence. Some evidence is presented which suggests that variations in body pressure are used to control the drag-line spinning, at least in the more primitive Araneomorphs. The drag-line plays a very important part in the life of a spider, ranging from a simple lifeline in the Salticids to a fundamental part of the complex web in the Argiopids. Its function is sometimes less clear in the more primitive spiders, for instance in the Gnaphosids and Clubionids which are typically nocturnal hunters, but even with these it may be a safety device. Spiders are a very varied group, and one might, therefore, expect to find equally varied uses for the drag-line in the different families, and even between the species

Elderly females of the spider Uloborus diversus (Uloboridae) spin webs which are different in various respects than those spun earlier in their lives. “Senile” virgins' webs differed from those of “senile” non-virgins' in several characteristics and in some ways resembled those of first instar nymphs.

The construction behaviour, design, and function of the orb webs of Uloboi sus are discussed in detail. The major phases and many of the details of construction behaviour are similar to the orb construction behaviour of some araneids. Frame threads are laid in a relatively fixed order, and are often made with a single set of movements repeated over and over. Radii and hub threads are laid after most of the frame threads are in place. Radii are connected to each other by the hub thread, and are actually continuous with it. A temporary spiral of non-sticky silk is laid starting at the hub and ending near the edge of the web. Tertiary radii are laid during construction of the temporary spiral and are continuous with it. Sticky spiral construction behaviour varies slightly with the site in the web but is very similar to that of Araneus diadematus. The behaviour of one leg following another in both time and space is described for the first time in spiders. Three types of web repair are described, one for the first time. The paths taken by spiders during radius construction (deduced from study of the hubs of completed webs), and the bending of radii by hub and temporary spiral threads suggest that all radii in a U. diversus web are not under equal tensions. The lack of secondary frame threads results in unequal stressing of some frame threads. Considerations of the structural properties of an orb imply these inequalities in tension probably lower web stability. The correlation between radius length and inter-radius angle, the sites of tertiary radii, and the bending of radii by the temporary spiral all indicate there has been selection to keep the distance between adjacent radii below some maximum value. Possible reasons for this are discussed. The outer loop of sticky spiral differs from those of many araneids in several respects, and probable functions of some of its characteristics are discussed. The site of the outer loop of sticky spiral is influenced by the site of the outer loop of temporary spiral. The spacing between loops of sticky spiral varies with radius length and with distance from the hub, but the functions of these variations are not clear. Changes in the average spacing between loops of sticky spirals on successive webs of individuals and in repair zones constructed the day of web construction imply that the spacing between loops of sticky spiral on a given web is probably influenced by the amount of silk available in the spider. The sticky spiral of U. diversus differs from those of all known araneids in not being attached to each radius it crosses, but the function of this characteristic is not clear. Many of the patterns in the web imply the spider adjusts its construction behaviour on the basis of cues received from its web. It appears that the spider can differentiate between sticky and non-sticky silk, and can sense the angles between radii while at the hub, the distance between radii and the distance to a frame thread during temporary spiral construction, the lengths of radii during sticky spiral construction, and probably the area to be covered by sticky silk and the amount of sticky silk available. There is evidence that adjustments are made on the basis of additional information, and possible sources of this information are discussed. Although the webs of U. diversus differ from the known webs of araneids in several respects, they do not give clear evidence that the family Uloboridae should be separated far from the family Araneidae. In general, there is more variation in web types within the Araneidae than between those of U. diversus and the araneids.

1. Uloborus begins web-weaving at an earlier developmental stage than other orb-weavers. 2. Uloborus spins the primary-type web until the first moult; after the moult it makes a normal web. 3. The primary-type web is an orb-web modification. Unlike the normal Uloborus web it lacks a viscid spiral; the temporary spiral is preserved in a completed web, and additional radii are placed besides the ordinary ones. 4. The pre- and post-moult spinning activities are similar in regard to radii, frame threads and temporary spiral placing. 5. The pre- and post-moult spinning activities differ in the performance of radial movements in place of spiral movements at the final spinning stage. 6. The change in the spinning activities takes place suddenly and is not connected with experience. 7. It is suggested that two factors are responsible for this change, one neural, the other the development of the structures, the cribellum and calamistrum.

The haploid number of chromosomes inStegodyphus sarasinorum (Eresidae) andUloborus plumipes (Uloboridae) is thirteen (11+X1X2) and ten (8+X1X2) respectively. The sex-chromosomes are of equal size in the former and unequal in the latter. All chromosomes are acrocentric in both species.

Uloborus diversus places extra silk (“stabilimenta”) near the hubs of its webs, preferentially on short radii ending near anchor threads. Spiders probably distinguish these radii from others by their relatively low extensibility. The stabilimentum probably functions as a camouflage device, and the orientation of the stabilimentum lines probably aids disturbed spiders in making quick exits from webs. Turning responses at radius-frame junctions during these exits are influenced by thread angles at the junctions (and possibly by other factors), and also enable disturbed spiders to reach hiding places quickly. The available data on other stabilimentum-building spiders suggests that they also use stabilimenta to provide defence against visually-hunting predators.

Capture threads may be defined as threads whose peculiar properties cause prey to adhere to them. With respect to these properties two types of capture threads may be distinguished: 1. Capture threads whose suitability for holding prey is based upon a covering that consists of a viscous glue. These threads are sometimes called sticky or adhesive threads. However, these characteristics can also be attributed to the other type of capture threads. Therefore, capture threads belonging to this first type will be called gluey capture threads in this review. 2. Capture threads whose suitability for holding prey is based upon a covering that consists of innumerable, extremely fine fibrils. They are often called hackled bands or hackled silk because of their characteristic appearance. Since the fibrils originate from the cribellum, these capture threads are also spoken of as cribellate threads or cribellar silk. However, these terms are ambiguous: cribellate spiders produce a variety of threads, which are not at all capture threads, and cribellar silk denominates only a component of these capture threads. Therefore, the threads in question will be called cribellar capture threads in this review.

As pointed out in the “Introduction to Venomous Arthropod Systematics“, all spiders are, strictly speaking, poisonous, with the sole exception of the small family of Uloboridae, which has secondarily lost its poison; the substitutive glandular apparatus has been studied by Glatz (1969).

In principle, with the exception of some groups of spiders which have no venom glands at all (e.g. Uloboridae and Holarchaea) all spiders with any kind of venom apparatus must be considered as venomous, if not always for man, then perhaps for other animals, or at least for insects, their usual prey. Vachon (1968) considered only about 100 spider species as actually dangerous to man. According to Sutherland (1981), about 100 species of Australian spiders may bite man, however, this does not, of course, mean that all of them are dangerous. A spider is not necessarily venomous to man due to different reasons: (1) their venom does not contain toxic fractions which affect mankind; (2) the quantity of the venom which the spider injects is insufficient; (3) their chelicerae are not strong enough to penetrate the human skin; (4) they are too timid to come into contact with man; (5) they have not had the opportunity of contact due to their lifestyle, i.e. contact may have been accidental, therefore their venomosity has not been recorded. Examples of the last consideration are the “new” venomous species which are still being “discovered”, e.g. the theridiid Steatoda paykulliana (Maretic et al. 1964) or the theraphosid Pterinochilus sp. (Maretic 1967). According to Russell and Gertsch (1982) the number of such new venomous spiders in the United States has increased to about 60 species.

Background: Ariston O. P.-Cambridge, 1896 and Siratoba Opell, 1979 are two poorly known genera of the spider family Uloboridae, which together comprise six nominal species previously described. This study provides an update of the taxonomic status for both genera and the description of two new species for Ariston. Results: The male of Ariston albicans O. P.-Cambridge, 1896 is described and illustrated for the first time, based on specimens from Chiapas, Mexico; Ariston reticens Gertsch & Davis, 1942 is transferred to Siratoba, and Siratoba sira Opell, 1979 is considered its junior synonym; Ariston spartanus n. sp. is described based on male and female collected in Caicubi, state of Roraima, Brazil; and Ariston aglasices n. sp. is described based on a female collected in Bonampak, Chiapas, Mexico. Conclusions: An emended diagnosis for Ariston and Siratoba and for each previously known species is provided. In total, five species are recognized in Ariston, including two new species, and two species are recognized in Siratoba.

An interspecific association between two spider species (Araneae, Uloboridae and Tengellidae) was studied over a sixweek period at an Atlantic lowland wet forest site in Costa Rica. The uloborid Philoponella vicina builds orb webs among the frame lines of the platform web constructed by Tengella radiata Kulczynski, the much larger tengellid species. Experiments with marked P. vicina determined that these uloborids actively choose to build in T. radiata webs. Studies of possible advantages the uloborid may derive from inhabiting the web of the tengellid showed that: 1) "Associated" uloborids persisted at a web site significantly longer than "solo" uloborids; 2) prey capture was significantly greater for the "associated" uloborids than for the "solo" spiders. The association of P. vicina and T. radiata appears to be commensal. As SOLITARY PREDATORS, most spiders are intolerant of conspecifics; even potential mates are sometimes treated as prey. While conspecific associations are known for sub-social, communal, and social spiders (Muma and Gertsch 1964; Pain 1964; Darchen 1965; Dennis 1965; Lubin 1974; Buskirk 1975; Brach 1977; Burgess 1976, 1979; Jackson and Joseph 1973), reports of interspecific associations in the literature are rare and anecdotal (reviewed by Kasto,n 1965). Within the family Uloboridae, however, tolerance olf conspecifics is common (Muma and Gertsch 1964; Eberhard 1971; Buskirk 1981), and several species are known to form commensal and slightly parasitic associations with other spiders (Struhsaker 1969, Bradoo 1972, Opell 1979). I report here on a neotropical association between Philoponella vicina 0. Pickard-Cambridge, a uloborid orb weaver, and Tengella radiata Kulczynski, a tengellid platform weaver, and present evidence that the association is advantageous to, the uloborid. This study attempted to test the nature of the association and addresses the following questions: 1) Do P. vicina actively select T. radiata webs as web sites? 2) Is prey capture in "associated" uloborids higher than in unassociated ("solo") ones? 3) Do tengellid webs offer greater protection from predation than other sites? 4) Do tengellid webs offer uloborids potential site positions in areas where they could otherwise not build? The interspecific association observed may be the result of an active search by uloborids for tengellid webs, or it may result from higher mortality of uloborids which establish themselves outside tengellid webs, or both. An affirmative result of a test of (1) above would indicate that uloborids are using some cue to locate the tengellid webs, and that the association is not merely the result of differential mortality of uloborids. If site selection is an active process in uloborids, one may presume that the spiders derive some advantages in inhabiting the web space of the tengellids. Tests of questions (2), (3), and (4) were designed to determine whether correlates of fitness, such as lower predation or higher rate of prey capture, differ significantly between uloborids building webs inside and outside of ten

On teste la prediction d'une relation positive entre la taille d'un insecte et le nombre d'araignees impliquees dans sa capture. On recherche aussi la repartition des tailles et des taxons parmi les insectes captures, s'il existe une relation entre la taille de la proie et le nombre d'airaignees s'en nourrissant et si la probabilite de s'echapper de la toile est reliee a la taille de la proie

Scanning electron microscope and light microscope studies show that each side of the Hyptiotes cavatus female genitalia has a spherical gland and a copulatory bursa which terminates in a long, looped sperm duct. Both components have adjacent openings into the vagina. The lack of secretory tissue associated with sperm ducts suggests that accessory glands function in sperm activation or another aspect of fertilization. A broad, median vaginal invagination with no direct connection to other components nor any associated secretory tissue appears during mating to accommodate the unusually long median apophysis spur of the male's pedipalpus. Separate bursal and sperm duct openings categorize this species as entelegyne, but the proximity of these openings suggests that Hyptiotes typifies an early transitional state in spider female genitalia. Because of anatomical complexity, internal features of the female genital apparatus of Hyptiotes Walckenaer, 1937 have been contested (Muma & Gertsch, 1964; Opell, 1979; Wiehle, 1927). Although the problem stems largely from unresolved details, its solution bears on the larger issues of the evolution of spider genitalia and their use in phylogeny and classification. Primitive (haplogyne) genitalia consist of single or paired blind spermathecae that connect to the vagina near its opening, whereas advanced (entelegyne) genitalia feature a unidirectional system with the opening of each commonly paired copulatory bursa leading to a seminal receptacle (spermatheca) which empties via a fertilization duct into the vagina (Baum, 1972; Brignoli, 1975; Cooke, 1970; Kraus, 1978). In haplogynes, the male intromittent organ (embolus of the pedipalpus) is inserted into the vagina; in entelegynes, it enters one of the secondary or displaced openings on the posterior or ventral surface of the female genital region. Although haplogyne and entelegyne conditions have been used to separate 1 I thank C. Bradford Calloway for help with histological techniques. National Science Foundation Grant DEB-8011713 supported scanning electron microscope use. TRANS. AM. MICROSC. Soc., 102(2): 97-104. 1983. ? Copyright, 1983, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.141 on Sun, 11 Dec 2016 04:30:54 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC. major spider taxa (Gerhardt & Kastner, 1938; Kaestner, 1968; Kaston, 1948; Simon, 1892; Wiehle, 1953), such schemes have not received complete acceptance (Bonnet, 1959; Bristowe, 1938; Lehtinen, 1967; Levi, 1982; Petrunkevitch, 1933). Some workers have considered the possibility of an intermediate or semientelegyne condition (Brignoli, 1975, 1978; Wiehle, 1967), and others view the entelegyne condition as potentially convergent (Opell, 1979; Platnick, 1975; Shear, 1978). The Uloboridae show that a single, universally recognized family can embrace members with both haplogyne and entelegyne female genitalia and that these grades of organization, however useful in understanding spider evolution, are less useful in higher classification than was traditionally thought. Although most of its members are clearly entelegyne, the family's most primitive genera, Tangaroa Lehtinen, 1967 and Waitkera Opell, 1979, have haplogyne female genitalia (Opell, 1979, 1983). Unless one considers their genitalia reduced or Uloboridae as the sister group of all other entelegyne spider families, at least one case of entelegyne convergence