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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

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