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The parasitoid-host association between Orgyia antiqua(Linnaeus) (Lepidoptera: Lymantriidae) and Carceliaatricosta Herting (Diptera: Tachinidae) is recorded here for the first time in Italy. A single caterpillar of O. antiqua wascollected in Northern Italy (Arzergrande, Padua, Veneto Region) in June 2015. After the specimen died, a single tachinidlarva emerged and pupariated. The emerged parasitoid was identified using DNA barcoding, with DNA extracted from thetachinid pupa. This is the first distributional record of C. atricostain Northern Italy and the second for Italy, only two otherspecimens having being recorded previously (Abruzzo Region, Central Italy).

Transgenic lines of silver birch (Betula pendula) carrying the sugar beet chitinase IV gene were used to study the effects of the heterologous expression of a transgenic chitinase on the performance of lepidopteran herbivores. The effect of wounding the leaves of birch on the performance of lepidopteran larvae and the growth of trees was also studied. Larvae of Orgyia antiqua L., Lymantriidae, and Phalera bucephala L., Notodontidae, were separately fed on the leaves of transgenic and wild-type birch, and their performance measured using nutritional indices. The relative growth rate (RGR) of O. antiqua larvae fed transgenic leaves was significantly lower than that of larvae fed wild-type leaves. Furthermore, there is little evidence that transgenic chitinase affects sur- vival but it was lowest for the group of larvae fed leaves with the highest expression of chitinase IV. Wounding did not have a sig- nificant effect on the performance of the larvae or on the growth of the branches of the trees. The growth of branches of particular transgenic lines, however, was significantly associated with tree line. The performance of P. bucephala larvae fed leaves of trans- genic and wild-type birches did not differ. The leaves used in both experiments from transgenic trees were shorter than those from wild-type trees. Using transgenic birch expressing sugar beet chitinase IV to improve the resistance of birch to fungal diseases can have negative effects on O. antiqua larvae feeding on the leaves of these birches. P. bucephala, however, was not similarly affected, which indicates that these two ecologically similar lepidopteran species may differ in their response to transgenic chitinase.

Environmental perturbations such as starvation and poor diet often prevent animals from attaining their optimal sizes. When the perturbation has a transient char- acter, compensatory responses are expected in terms of faster growth or a prolonged developmental period. In the case of insect larvae, details of such responses are insuf- ficiently known at the proximate level. Attention to responses at the level of particular larval instars should promote an understanding of insect developmental plasticity also in a more general context. To provide an instar-specific analysis of compensatory growth, larvae of the moth Orgyia antiqua (L.) are reared on inferior diet during one larval instar. Responses in growth parameters are recorded in the course of the manipulated instars, as well as at the level of the entire larval period. The negative relationship between development time and size in response to the inferior food quality, typical of the entire larval periods, is also observed within the manipulated instars taken separately. The manipulated larvae remain smaller than the larvae of the control group (significant in males only), even by the end of the subsequent instar during which all individuals are provided with superior host. In males, close to full size compensation by the time of pupation is achieved only by means of adding an extra larval instar. The inability of larvae to fully compensate during one and even two instars is considered as an indication of the presence of constraints on the within- instar growth pattern. An alternative, adaptational explanation for the incomplete compensation could be based on the cost of prolonged development period. Given the ecological context of the species' life history, such an explanation appears less likely.

The structural organization of the eyes belonging to 12 winged male and 12 wingless female Orgyia antiqua moths, exposed for 1 h to UV-radiation (lambda(max)=351 nm) of 1.4 kW/m2, was compared with that of 12 male and 12 female non-irradiated control specimens. Following the UV-exposure, the screening pigments were found in a position indicative of extreme light-adaptation. Extensive formations of vesicles along the perimeter of the cones as well as disintegrating ER in the cone cytoplasm were noticeable, especially in the eye of the female. On the retinal side of the clearzone, the microvilli of the rhabdoms had become affected by the UV in characteristic ways: in the male eye, retinal cell damage in the form of microvillar swellings and disintegrations were largely confined to just two cells per ommatidium, placed opposite to each other. The female eye, once again, exhibited greater vulnerability and more widespread microvillar disruptions that affected all of the ommatidial retinula cells. The greater resistance of the eye of the male to an exposure with UV makes sense, if we consider the consequences of the retinal damage, which would clearly be a more severe handicap for an actively flying individual than for an almost sedentary one like the wingless female.

The vapourer moth (Orgyia antiqua L.) is a polyphagous pest occuring on many trees and bushes, including apple, currants and raspberry. In 2013 and 2014 monitoring of this pest using pheromone traps to attracting males was carried out in apple orchards at the Research Institute of Horticulture. Butterflies of the vapourer moth were caught on pheromone traps placed in all monitored orchards however: there was no damage to the leaves caused by caterpillars. Adult flight of O. antiqua usually began in the second half of June and ended in late of October or even early November. The second generation of butterflies was more numerous in monitored orchards than the first one. The main flight of males of the first generation took place in July and another in September. The vapourer moth population was not abundant in the monitored orchards and there was no need to control it.

Intraspecific color polymorphism is widespread in insects, and various mechanisms have been proposed to explain its maintenance. Some explanations rely on the effect of body color on the organism's thermal physiology. Darker individuals accumulate solar energy more efficiently, and therefore, dark body coloration in insects is frequently presumed to be an adaptation to low temperature conditions. However, it is largely unclear what is the importance of the thermal biology in comparison to other potential selective forces on body coloration. In this study, we evaluated the role of temperature as a potential selective factor maintaining color polymorphism in aposematic larvae of the moth Orgyia antiqua L. It was found that darker, and thus less aposematic, larvae accumulated solar energy more efficiently. However, in a set of laboratory and outdoor experiments, we found no evidence of temperature-dependent performance of different color morphs or in development of different morphs induced by rearing temperature. We conclude that the effects related to thermal physiology are not likely important determinants of optimal coloration in O. antiqua. The reasons may lie in high mobility of the larvae, which allows for effective behavioral thermoregulation, which is also shown in this study. Our results caution against an uncritical extrapolation of results obtained for model organisms and indicate the need for giving more attention to the species-specific ecological background in ecophysiological studies.

While the study of colour patterns is a traditional subject of evolutionary ecology, there are various hypotheses which suffer from a lack of experimental evidence. One intriguing possibility is a trade-off between warning efficiency and detectability. After a certain size threshold, the detrimental effect of increased detectability can outweigh the benefits of warning colouration. One may thus expect corresponding patterns at the level of ontogenetic development: as juveniles grow, they should first acquire warning colouration, and then lose it again. We analysed this possibility in Orgyia antiqua, a moth species with hairy larvae which are poly- phenic with respect to the intensity of warning colouration. We detected a regular change in colour patterns through larval life. Indeed, the larvae tend to display warning colouration at intermediate sizes while dull colours dominate in fully grown larvae. In aviary experiments, we confirmed that the colourful phenotype is the one that causes the strongest aversion in birds. Nevertheless, the effect was rather weak and most of the larvae were still eventually consumed when found. Unexpectedly, for human subjects, the warningly coloured larvae were harder, and not easier to find among natural vegetation, most likely due to the disruptive effect of the aposematic colour pattern. Importantly, the trend was reversed in the largest size class, suggesting that the disruptive colouration loses its advantage as the larva grows. This is consistent with the actual patterns of size-dependence of colouration. We present evi- dence against an alternative explanation which relates size-related change in colouration to behavioural changes prior to pupation. We conclude that even if the efficiency of the warning effect plays a role in determining the size-dependence of colouration, the pat- tern may be largely explained by the effects of size-dependent detectability alone.

Carotenoid-based integumental coloration is often associated with individual performance in various animals. This is because the limited amount of the pigment has to be allocated to different vital functions. However, most of the evidence for the carotenoid-based trade-off comes from vertebrate studies, and it is unclear if this principle can be applied to insects. This possibility was investigated in Orgyia antiqua L. (Lepidoptera: Lymantriidae). The larvae of this species are polyphenic in their coloration, varying from a highly conspicuous combination of yellow hair tufts on black background to cryptic appearance with brown hair tufts. The conspicuous larvae are aposematic, advertising their aversive hairiness. The maintenance of different colour morphs in O. antiqua requires explanation, as an aposematic signal is expected to evolve towards monomorphism. Chromatographic analysis showed that the yellow coloration of the hair is based on the carotenoid pigment lutein ( α -carotene3,3’-diol). The colour of hair tufts was dependent on their carotenoid content. This justifies an expectation of carotenoid-based physiological trade-offs between aposematic coloration and individual performance. To test this hypothesis, we monitored life histories of differently coloured larvae reared on various host plants, recording their body sizes, growth rates, and mortalities in each instar. There was a significant but relatively low heritability of tuft coloration, which allowed us to expect environmental effects. We found no phenotypic associations between hair tuft colour and performance indices in O. antiqua larvae, neither did the quality of host plant affect the frequency of colour morphs. However, the frequency of colour morphs differed between larval instars. Our results suggest that carotenoidmediated physiological trade-offs are not involved in the maintenance of colour morphs in O. antiqua larvae, and factors other than individual condition should be responsible for the observed variability.

Structure and photomechanical changes upon light/dark adaptation in the superposition compound eyes of the highly sexu- ally dimorphic Orygia antiqua were studied by light and electron microscopy. The eyes of the fully winged male differ from those of the wingless, sedentary female in several respects: they are significantly larger, display a more regular ommatidial array, have a wider clearzone and possess a much more substantial tracheal tapetum. However, the eyes of the female exhibit more pronounced photomechanical changes upon light/dark adaptation than those of the male. We believe that for females, on account of their limited mobility, it is necessary that their eyes can cope with widely fluctuating brightnesses, but that visual sensitivity and resolving power are less important to them than to the actively flying males. Although the latter may be attracted to the females by pheromones, males in their diurnal searches will have to visually avoid obstacles and predators. Moreover, because of their ability to fly, males can seek shelters or shaded areas and unlike the sedentary females avoid prolonged exposures to potentially hazardous light levels. This could explain why the eyes of the females exhibit more pronounced photomechanical responses to changes in ambient light lev- els.

While the ultimate causes and adaptive significance of sexual size dimorphism (SSD) have been extensively studied, the developmental mechanisms behind this phenomenon have received little attention. Going through an additional larval instar may form a specific way of achieving SSD in arthropods. In the present study, the mechanisms of SSD determination of two lymantriid moths, with marked SSD, were studied. In both species, females tended to go through an additional instar compared to males, and form pupae that were more than twice the weight of the males. To reveal the role of an extra instar, larval growth was monitored in the laboratory and the growth parameters were analysed as dependent on sex and developmental type (number of instars). Prolonga- tion of growth by means of adding an additional larval instar in females turned out to be the key mechanism in the determination of the highly female-biased SSD in the species studied. There is thus a developmental mechanism available that permits achieving a larger size by means of extending the growth period. This provides evidence against constraint-based evolutionary explanations for body sizes in insects. There was no considerable accumulation of SSD during earlier larval life when females went through more instars than males. In contrast, in those cases in which males and females had the same number of instars, SSD accumulated gradu- ally during the course of several larval instars. Longer growing period turned out to be a crucial mechanism leading to the female- biased SSD even when instar number did not differ between sexes, although higher instantaneous relative growth rates of females also played a complementary role in the latter case. Within sexes, an additional instar was characteristic of initially smaller larvae, as predicted by the "threshold size" hypothesis.

Many risks and environmental concerns have been linked with the cultivation of genetically modified (GM) trees. Among the most frequently mentioned risks are the unintentional/pleiotropic effects of transgenes on organisms or plant properties that are not the targets of genetic modification. Risks in forest ecosystems are difficult to predict, due to the long life cycles of trees and their complex ecological interactions. This thesis is focused on the interactions between insect and mammal herbivores and transgenic trees. The studied silver birch (Betula pendula Roth) carried a sugar beet chitinase IV gene and the aspen and hybrid aspen (Populus sp.) carried a pine pinosylvin synthase gene, both aiming to improve the trees resistance to fungal diseases, but also potentially affecting insect and mammal herbivores. Tree growth and quality, and insect density and composition were studied during the field trial. The palatability of transgenic trees was studied in the feeding experiments using the lepidopteran herbivores rusty tussock moth and buff-tip (Orgyia antiqua L., Phalera bucephala L.) and the mammalian herbivores mountain hare and roe deer (Lepus timidus L., Capreolus capreolus L.). The studies revealed that sugar beet chitinase IV caused unintentional effects on silver birch: the transgenic trees were smaller and their red leaf colour indicated stress. There were differences in herbivore pressure between transgenic and wild-type birches: GM trees had a higher aphid density but a lower diversity of insect species and visible leaf damages. The relative growth rate of O. antiqua on transgenic birches was lower in comparison to wild-type birches. No difference in the palatability to mammals was found between transgenic and wild-type trees. The results suggest that the impact on herbivores is species- dependent. The pleiotropic effects of the transgenes affecting plant-herbivore interaction can explain these impacts. These results should be taken into account when considering the biosafety of GM trees. Siirtogeenisten puiden (GM-puut) kasvatukseen liittyy riskejä ja ympäristöongelmia. Yksi suurimmista riskeistä liittyy siirtogeenisen aineksen pleiotrooppisiin tai tahattomiin vaikutuksiin, jolloin yksi geeni voi vaikuttaa useampaan kuin yhteen fenotyypin ominaisuuteen. Siirtogeenin vaikutuksia on vaikeaa ennakoida monimutkaisessa metsäekosysteemissä kasvaviin pitkäikäisiin puihin ja niitä ravintonaan käyttäviin eläimiin. Tässä väitöskirjassa tarkasteltiin kasvinsyöjähyönteisten ja -nisäkkäiden ja siirtogeenisten puiden, rauduskoivun (Betula pendula Roth) ja haapojen (Populus sp.) välisiä vuorovaikutuksia. Koivuun oli siirretty sokerijuurikkaan kitinaasia ja haapoihin männyn pinosylviinisyntaasia tuottava geeni. Siirtogeenit oli siirretty puihin sienitautiresistenssin parantamisen tutkimiseksi. Tutkittujen siirtogeenien tuottamat aineet saattavat tahattomasti vaikuttaa puiden kasvi-kasvinsyöjävuorovaikutukseen, kuten kasvinsyöjäkestävyyteen. Tämä johtuu kitinaasin kyvystä hajottaa kitiiniä, joka on paitsi sienten soluseinän myös hyönteisten keskeinen rakenneosa. Pinosylviini taas on puun puolustusaine mm. sieniä ja nisäkkäitä vastaan. Kenttäkokeella selvitettiin, poikkeavatko siirtogeenisten koivujen kasvulliset ja laadulliset ominaisuudet ja niiden kohtaama hyönteissyönti kontrollipuista. Syöttökokeissa tutkittiin siirtogeenisten puiden kelpaavuutta ravintona perhosille täplätupsukas ja härkäpää (Orgyia antiqua L., Phalera bucephala L.) sekä nisäkkäille metsäjänis ja metsäkauris (Lepus timidus L., Capreolus capreolus L.). Sokerijuurikkaan kitinaasi IV -siirtogeeni aiheutti puille ennakoimattomia vaikutuksia: Niiden kasvu oli heikompaa kuin kontrollien ja niiden lehtien punainen väritys indikoi stressiä. Heikompi kasvu selitti koivun ruskotäpläkärpäsen alempaa esiintymistiheyttä siirtogeenisillä puilla. Herbivoripaine erosi siirtogeenisten ja kontrollipuiden välillä: Siirtogeenisillä puilla esiintynyt lajisto ja lehtivauriot olivat yksipuolisempia, mutta kirvatiheys suurempi kuin kontrollipuilla. O. antiquan suhteellinen kasvu oli heikompaa siirtogeenisellä kuin kontrolliravinnolla. Nisäkkäiden syöttökokeissa siirtogeenisten ja kontrollipuiden välillä ei ollut eroa maistuvuudessa. Tulokset viittaavat siihen, että tutkittujen GM-puiden vaikutukset herbivoreihin ovat lajiriippuvaisia. Vaikutusten taustalla voivat olla siirtogeenin pleiotrooppiset vaikutukset, jotka vaikuttivat kasvi-herbivori-vuorovaikutukseen. Tulokset tulisi ottaa huomioon GM-puiden riskinarvioinnissa.

Strong correlation between female body size and potential fecundity is often observed in insects. Directional selection favouring increased body sizes is thus predicted in the absence of opposing selection pressure. The evolutionary forces capable of counterbalancing such a 'fecundity advantage' are poorly documented. This study focuses on revealing the costs of large body size in the wingless females of Orgyia antiqua and O. leucostigma, two related species of lymantriid moths. Extreme behavioural simplicity of these animals allows systematic assessment of various fitness components in conditions that are close to natural. A linear relationship between pupal weight and potential fecundity was observed. This association was found to be independent of particular rearing conditions. There was no evidence that the relationship between fecundity and body mass becomes asymptotic when body sizes increases. No component of fitness showed a negative phenotypic correlation with body size; some displayed a weakly positive one. In particular, pupal mortality, adult longevity, mating and oviposition success, as well as egg hatching rate and egg size, were established as independent of body size in a series of field and laboratory experiments. There was a very high overall efficiency of converting resources accumulated during the larval stage to egg masses. With no costs of large adult size, selective forces balancing the fecundity advantage should operate in the course of immature development. The strong dependence of realized fecundity on body size is considered characteristic of the capital breeding strategy.

Aphantorhaphopsis samarensis (Villeneuve), a European tachinid, has been released in North America for classical biological control of the gypsy moth, Lymantria dispar (L.). This study examined the host range of A. samarensis. We used three approaches: (1) field collection and rearing of potential alternate or alternative hosts at European sites where A. samarensis was known to occur, (2) choice tests offering females of A. samarensis both gypsy moth and native North American species of Lepidoptera, and (3) host suitability tests in which we artificially inoculated European nontarget species with mature eggs of A. samarensis dissected from gravid females. In the field studies, we collected a total of 851 caterpillars, belonging to at least 54 species other than gypsy moth in 11 families, over several years, but none yielded A. samarensis, with the possible exception of a single larva of Lymantria monacha (L.) and the rusty tussock moth, Orgyia antiqua (L.), which yielded puparia resembling those ...

The first characterization of a nucleopolyhedrovirus (NPV Baculoviridae) isolated from the vapourer moth, Orgyia antiqua (Lepidoptera Lymatriidae), in the United Kingdom is presented. Transmission electron microscopy revealed that the virus nucleocapsid rods were singly enveloped in the polyhedron inclusion body (PIB) so that the virus is assigned to the SNPV subgenus of the Baculoviridae. Restriction endonuclease analyses of viral DNA indicated a genomic size of approximately 148 kb. Restriction profiles of O. antiqua SNPV closely resembled those of heterologous NPVs isolated from four different Orgyia species and was most similar to a North American SNPV isolate from the Douglas-fir tussock moth, O. pseudotsugata. In host range tests, O. antiqua SNPV was not infectious to 23 lepidopteran species representing four families. Heterologous Orgyia NPV isolates were permissive in O. antiqua larvae. Using a diet plug bioassay method, the median lethal dose response (LD50) for this virus in second and third instar O. antiqua larvae were estimated at 52 and 539 PIBs per larva, respectively. r 1999 Academic Press

In 1990, natural infestations of the polyphagous vapourer moth, Orgyia antiqua (Lepidoptera: Lymantriidae) in lodgepole pine plantations in northern Scotland, were studied to ascertain the role of host foraging behaviour on the prevalence of nucleopolyhedrovirus (NPV; Baculoviridae) infection in the population. Aerial dispersal of early instar larvae (L1-L3) from the tree canopy onto heather foliage at the forest understorey, with subsequent relocation back onto the tree as late-instar larvae (L4-L6) appeared to play a significant role in the development of a widespread virus epizootic in which approximately 80% of L4-L6 individuals succumbed to disease. Bioassays of foliage 1 year later showed that the distribution of NPV followed a pronounced vertical gradient through the forest canopy culminating in high concentrations of virus in the forest understorey. Experimental systems comprising potted pine trees positioned above heather bases showed that NPV infections could be acquired by early stage larvae following dispersal from the tree and feeding on the undercanopy vegetation, then translocated to the tree component for secondary transmission to susceptible tree-feeding individuals. Behavioural studies indicated that the tendency for first-, second- and third-instar larvae to disperse to the understorey was probably not influenced by larval density on the tree but was strongly dependent on larval instar. In contrast, the tendency for larvae to relocate from the understorey heather to the tree was affected by both larval density and larval instar, suggesting that both these factors may significantly affect virus acquisition, translocation and transmission in the host population. In the present study, the heather understorey appeared to act as a pathogen reservoir in which virus could persist between host generations. Spatial heterogeneity in virus distribution combined with host foraging behaviour (dispersal and feeding) resulted in the pathogen playing a major role in host population dynamics over an extended time period (3 years). The reservoir theory is supported by the observation that similar dynamics were not observed in O. antiqua populations at neighbouring sites which lacked understorey food plants.

The responses of transcriptome and phenolic compounds were determined with Populus tremula L. × Populus tremuloides Michx. expressing the hemoglobin (Hb) of Vitreoscilla (VHb) and non-transformant (wt) line. After 24-h exposure of leaves to Conistra vaccinii L., the transcript levels of endogenous non-symbiotic class 1 Hb (PttHb1) and truncated Hb (PttTrHb) genes were modestly reduced and increased, respectively, in both wt and VHb-expressing line. Besides the herbivory exposed leaves showing the most significant transcriptome changes, alterations were also detected in the transcriptome of nonorthostichous leaves positioned directly above the exposed leaves. Both wt and VHb-expressing line displayed similar herbivory-induced effects on gene expression, although the extent of responses was more pronounced in the wt than in the VHb-expressing line. The contents of phenolic compounds were not altered due to herbivory and they were alike in the wt and VHb-expressing line. In addition, we determined the relative growth rates (RGRs) of Orthosia gothica L., Ectropis crepuscularia Denis & Schiff. and Orgyia antiqua L. larvae, and found no variation in the RGRs between the lines. Thus, VHb-expressing P. tremula × tremuloides lines showed to be comparable with wt in regards to the food quality of leaves.

The role of pathogens in insect ecology is widely appreciated but remains insufficiently explored. Specifically, there is little understanding about the sources of the variation in the outcome of insect-pathogen interactions. This study addresses the extent to which immune traits of larvae and pupae of the mothOrgyia antiquaL. (Lepidoptera: Lymantriidae) depend on the host plant species and individual condition of the insects. The two host plants,Salix myrsinifoliaSalisb. andS. viminalisL., were chosen because they differ in the concentration of phenolic glycosides, harmful to most polyphagous insects. Individual condition was assumed to be reflected in body weight and development time, and was manipulated by rearing larvae either singly or in groups of four. The resistance traits recorded were survival and time to death after fungal infection in the larval stage and the efficiency of encapsulating a nylon implant by the pupae. The survival of the infected larvae was mainly determined by the species of the host plant. Encapsulation response was not associated with the resistance to the pathogen, suggesting that the host plant affected the pathogen rather than the immune system of the insect. Interestingly, the host plant supporting better larval growth led to inferior resistance to the pathogen, indicating a trade-off between different aspects of host plant quality.

Cross-infections of L. dispar by a nuclear polyhedrosis virus of O. antiqua (OaNPV) showed that there is not only a dosage-related, but even an absolute difference in susceptibility to the virus depending on host races. The passage of the virus strain OaNPV through a susceptible chinese race of L. dispar induced genetically fixed modifications of the virus-polyhedrins and an enlargement of the host range. Further passages led to a race-specific adaptation of the modified virus strain to the host L. dispar in general. Cross-breeding experiments with a replicating and a non-replicating race of L. dispar demonstrated that the special susceptibility to OaNPV and the ability to modify the virus strain is dominantly passed on the next generation by both sexes. Zusammenfassung Zur Empfindlichkeit verschiedener geographischer Rassen des Schwammspinners (Lymantria dispar L.; Lep., Lymantriidae) gegenuber einer Kernpolyedrose des Schlehenspinners (Orgyia antiqua Hbn.; Lep., Lymantriidae) Aus Infektionsversuchen mit dem Schlehenspinnervirus (OaNPV) auf die Schwammspinnerherkunfte “Wurzburg”, “Peking” und “Teheran” ergaben sich grundsatzliche Empfindlichkeitsunterschiede der geographischen Rassen: von ganzlicher Unempfindlichkeit, uber Mortalitat ohne Polyederbildung, bis zu Mortalitat mit Ausformung von Einschliesungskorpern. Durch die Passage von OaNPV uber die empfindliche Pekinger Rasse wurde der Virusstamm derart verandert, das er auch Pathogenitat fur andere Schwammspinnerrassen erlangte. Die genetische Modifikation des Virusstammes lies sich mit Hilfe der Gel-Elektrophorese in Form einer veranderten Zusammensetzung der Polyederproteine nachweisen. Diese Wirtsspektrumserweiterung erwies sich als neue, stabile Eigenschaft, die uber wechselnde Kombinationen von Infektionspassagen erhalten blieb. Die Wirkung auf den autochtonen Wirt Schlehenspinner wurde hierdurch nicht beeintrachtigt. Zudem erfolgte, besonders bei Infektionsserien uber die gleiche Herkunft, eine rassenspezifische Adaptation des Virusstammes in Form einer Virulenzsteigerung. Von besonderer Bedeutung ist die Beobachtung, die an Rassenhybriden zwischen den Herkunften “Wurzburg” und “Peking” gemacht werden konnte. Es zeigte sich, das nicht nur die Empfindlichkeit gegenuber dem Virusstamm OaNPV, sondern auch die Fahigkeit zu dessen Modifikation im Sinne einer Wirtsspektrumserweiterung durch beide Geschlechter der Pekinger Elterntiere auf die Kreuzungsnachkommen vererbt wird.

The restructuring of spermatocytes during the first meiotic division is examined in the moth Orgyia antiqua (Lymantriidae, Lepidoptera) using transmission electron microscopy. Particular emphasis was placed on the behaviour of the perispindle membrane system. These membranes develop from layers of smooth endoplasmic reticulum wrapped around the prophase I nucleus and are retained until early telophase I. The original nuclear envelope is dissolved in metaphase I. Polar fenestrae in the perispindle membrane stacks are filled with numerous irregular membrane elements. The formation of new nuclear envelopes around the daughter nuclei takes place inside the perispindle membrane system. Finally, the membrane stacks rupture concomitantly with spindle elongation in late telophase I. Thus, division of primary spermatocytes in Orgyia antiqua has a surprising degree of similarity with the so-called closed mitosis. This mode of division is typical for many protozoa, algae and fungi. In the pertinent cells, the original nuclear envelope persists around the spindle area during nuclear division. In order to distinguish the closed mitosis from the situation in Orgyia antiqua spermatocytes, the term 'sheathed nuclear division' is suggested for the latter.

In the highly sexual-dimorphic nocturnal moth, Acentria ephemerella Denis & Schiffermuller 1775, the aquatic and win- gless female possesses a refracting superposition eye, whose gross structural organization agrees with that of the fully-winged male. The possession of an extensive corneal nipple array, a wide clear-zone in combination with a voluminous rhabdom and a reflecting tracheal sheath are proof that the eyes of both sexes are adapted to function in a dimly lit environment. However, the ommatidium of the male eye has statistically significantly longer dioptric structures (i.e., crystalline cones) and light-perceiving elements (i.e., rhab- doms), as well as a much wider clear-zone than the female. Photomechanical changes upon light/dark adaptation in both male and female eyes result in screening pigment translocations that reduce or dilate ommatidial apertures, but because of the larger number of smaller facets of the male eye in combination with the structural differences of dioptric apparatus and retina (see above) the male eye would enjoy superior absolute visual sensitivity under dim conditions and a greater resolving power and ability to detect movement during the day. The arrangement of the microvilli in the rhabdom of both genders suggests that their eyes are polarization-sensitive, an ability they would share with many aquatic insects that have to recognize water surfaces. Although sexual recognition in A. ephe- merella is thought to chiefly rely on pheromones, vision must still be important for both sexes, even if the females are wingless and never leave their watery habitat. Females swim actively under water and like their male counterparts, which fly above the surface of the water, they would have to see and avoid obstacles as well as potential predators. This, together with a small incidence of winged females, we believe, could be the reason why the eyes of female A. ephemerella are less regressed than those of other sexually dimorphic moths, like for instance Orgyia antiqua. Another, but difficult to test, possibility is that male and female A. ephemerella have diverged in their behaviour and habitat preferences less long ago than other sexually dimo rphic moths.

Fungal epizootics occurred in abundant Orgyia vetusta (western tussock moth; Lepidoptera: Lymantriidae) populations on Lupinus arboreus bushes growing on the Pacific coast north of San Francisco, California. The causative pathogen was isolated and identified as Entomophaga aulicae, Group II, based on RFLPs using rDNA and PCR-amplified rDNA products. Inability of this fungus to infect the lymantriid Lymantria dispar (gypsy moth) confirmed its distinction from Entomophaga maimaiga, the only other member of this species complex which predominantly infects lymantriids. Later instar wandering by O. vetusta in outbreak populations and close proximity of larvae in dense populations are characteristics most probably promoting development of E. aulicae epizootics; these life history patterns are also typical of Lymantria dispar populations experiencing epizootics of E. maimaiga.

Caterpillars of some moths feed gregariously, for at least part of their lives, in communal silken webs or ‘tents’ which they spin on their food plants. Some species which have this habit and are economically important in Britain are described here. These species are the small ermine moths (Yponomeutaspp.), the lackey moth (Malacosoma neustria (L.)) and the brown-tail moth (Euproctis chrysorrhoea (L.)). The vapourer moth (Orgyia antiqua (L.)), whose caterpillars occur together in large numbers though not feeding within webs, is also included.

On an outbreak of Orgyia antiqua L. (Lepid., Lymantriidae) at Memmingen, Bavaria, 1972. The number of larvae ofO. antiqua on pine trees at Memmingen reached its high level during autumn 1971. About 350 ha mainly the old trees were infested. The number of egg masses per stem was more than 42 in max. with an average of 205 eggs per egg mass (n = 40). The percentage of hatching was found to be 74,5%. The rest of the eggs was mainly parasitized byTelenomus dalmanni (Ratz.). The pest had only one generation. The old larvae were infected with a virus disease and a great part of pupae was killed by fungi. These two diseases were the main factors in regulating the population ofO. antiqua.

Zwei Laborpopulationen vonFormica polyctena (mit je 2000–3000 Arbeiterinnen und 2 Koniginnen) wurden Raupen vonOrgyia antiqua als Nahrung vorgesetzt. Die L1 bis L3 wurden von den Ameisen nicht als Beute erkannt. Von den L4 bis L6 wurden von Population A=49% und von Population B =77% durch Verzehr oder Verletzung vernichtet. Um die lang behaarten Raupen toten zu konnen, „rupften” ihnen die Ameisen zuvor die Haare.

Leaves of Betula were damaged artificially in April, June and August 1982. Palatability of damaged and adjacent undamaged leaves was assessed against controls in bioassays using the polyphagous Lepidoptera Spodoptera littoralis and Orgyia antiqua. Assessments were carried out at intervals from six hours to five months following each damage date. Palatability (relative proportions of leaves consumed) was significantly lower than controls in damaged and adjacent leaves after six hours and remained detectable for up to two months but this was less clear in the June-damaged samples and undetectable in the August group. Adjacent leaves were significantly affected whether distal or proximal to the damaged leaves. Marked and significant changes occurred in levels of soluble tannins in the damaged and adjacent leaves but the relationship between crude tannin levels and changed palatability was not simple cause and effect. No significant effects of damage on aphid (Euceraphis punctipennis) reproduction could be detected among birches in a growth room experiment in which half the trees were artificially damaged and half were controls. The results are discussed in the light of earlier work on induced defence in birch and five areas of significant new information represented by the results in this paper are identified.

MR. MCKAY'S letter in NATURE of January 16 (p. 247) is of interest in pointing out that some butterflies are normally exposed in flight to danger from certain birds. Nevertheless, I believe this to be exceptional so far as this country is concerned. At the present moment I have in my possession a specimen of the clay-flying moth Orgyia antiqua, which my friend Mr. D. F. Taylor saw seized when on the wing by a house-martin, which relinquished its hold in consequence of a luckily aimed stick from my informant. The left fore-wing shows plainly the mark of the bird's beak, which, however, did not tear the wing, but merely left a triangular area denuded of scales. So far as I am aware, house-martins do not, as a rule, feed on Lepidoptera, and this instance is probably to be regarded as a mistake on the part of the bird. It is possible that other isolated examples of similar mistakes may have been noticed, but their bearing on the general question of the coloration and markings of butterflies must be very slight.

A review is given of the recurrent outbreaks of the tentcaterpillar, Malacosoma neustria L., affecting the elm trees in the city of Amsterdam in the period 1930—1957. An outbreak of the brown tail moth, Euproctis chrysorrhoea L., in 1935—1936 is also mentioned and some occasional loss of foliage through the caterpillars of the vapourer moth, Orgyia antiqua L. Large fluctuations in the size of the Malacosoma populations were found. After some years in which the damage was negligeable, the increase always started in the N.W. part of the centre of the city. In the following years the outbreaks moved to adjacent parts of the centre and finally sometimes even to more eccentric parts (see Fig. 6—9). However, the occurrence of really harmful numbers of tentcaterpillars was mostly restricted to the centre of the town. The merits of the control measures which were carried out with derris/talcum powder spread by motordusters are discussed. The insecticide was thought to be the only sufficiently harmless for its use in the centre of a city. Some cases of defoliation and other inconveniences caused by the presence of crowds of caterpillars could apparently be reduced by the control measures. In several instances, however, the efficacy of the method remained doubtful. The urgency is stressed of further studies of the bionomics of Malacosoma under local conditions and some suggestions are made for a better organization of the measures applied.

Tussock moths of the family Lymantriidae are an important group of forest defoliators that characteristically have periodic outbreaks. The sex pheromone of the female Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), has been identified as (Z)-6-heneicosen-11-one (Smith et al. 1975) and shown to be sexually stimulating to males of seven tussock moth species in two genera, Orgyia and Dasychira (Daterman et al. 1976; Grant 1977). Laboratory tests demonstrated that this compound could disrupt mating of both the whitemarked tussock moth,O. leucostigma (J.E. Smith), and rusty tussock moth, O. antiqua (L.), when the adults were maintained in an atmosphere containing the chemical (Grant and Frech 1976). Subsequently field tests in small plots treated with the same material released into the atmosphere at a rate equivalent to 20-50 mg/ha/day demonstrated that pheromone communication of whitemarked tussock moths and a conifer-feeding tussock moth, Dasychira plagiata (Walker), could be disrupted in their natural habitat (Grant 1978). Similar disruption was obtained with field populations of the Douglas-fir tussock moth (Sower and Daterman 1977). The present report describes the disruptive effects of (Z)-6-heneicosen-11-one in the field on the pheromone communication of another species, the rusty tussock moth.

A review is given of the recurrent outbreaks of the tentcaterpillar, Malacosoma neustria L., affecting the elm trees in the city of Amsterdam in the period 1930—1957. An outbreak of the brown tail moth, Euproctis chrysorrhoea L., in 1935—1936 is also mentioned and some occasional loss of foliage through the caterpillars of the vapourer moth, Orgyia antiqua L. Large fluctuations in the size of the Malacosoma populations were found. After some years in which the damage was negligeable, the increase always started in the N.W. part of the centre of the city. In the following years the outbreaks moved to adjacent parts of the centre and finally sometimes even to more eccentric parts (see Fig. 6—9). However, the occurrence of really harmful numbers of tentcaterpillars was mostly restricted to the centre of the town. The merits of the control measures which were carried out with derris/talcum powder spread by motordusters are discussed. The insecticide was thought to be the only sufficiently harmless for its use in the centre of a city. Some cases of defoliation and other inconveniences caused by the presence of crowds of caterpillars could apparently be reduced by the control measures. In several instances, however, the efficacy of the method remained doubtful. The urgency is stressed of further studies of the bionomics of Malacosoma under local conditions and some suggestions are made for a better organization of the measures applied.