The difficulty of obtaining accurate and comparable measurements of the carotenoid content of plant and insect specimens is discussed. The carotenoids present in cabbage and in all stages in the life cycle of P. brassicas. were investigated: the carotenoids in the insect reflected those in the plant; male and female adults of P. brassicae seemed to possess similar amounts of carotenoids. In the plant there was a considerable variation in the carotenoids, both in quantity and in specificity. Age of the plant and season of growth were two factors, probably of several others, which were shown to influence the carotenoid content of the plant. The variation in the plant made it difficult to assess the significance of any variation in the earotenoids present in the insect. Feeding experiments showed that one larva during its life assimilated 77.79ug of b-carotene, which was 57.41% of the total b-carotene ingested. Of the total assimillted at least 66.10ug, that is 84.97%, was , Analysis of the frass indicated that greatest assimilation of p-carotene occurred at the end of the Lit larval stage. Labelling experiments seemed to show that carotenoids were sequestered from the haemolymph by the fat body four hours after ingestion. The carotenoid content of several other species of lepidoptera was determined. The results were often based on very different samples and therefore could not give reliable information about differences in amounts of carotenoid in the different species. However, they showed that earotenoids were present in all species studied. Lutein and b-carotene, two of the major plant carotenoids were found in all species in which individual carotenoids were determined and in all but examples either lutein or b-carotenewas the principal carotenoid in the insect. In species where males and females were available there was no apparent difference in the amount of carotenoids in the two sexes. Total carotenoids per -insect was shown to be positively correlated with the dry weight of the insect. Possible functions of earotenoids in insects are discussed, in particular as a source of vitamin A, in colouration and involvement in olfaction and toxicity.

No description available.

The objective of this work was to investigate whether or not olfactory clues play a role in host plant location by the polyphagous moth, Helicoverpa armigera. Volatiles collected from flowers of African marigold, Tagetes erecta, and sweet pea, Lathyrus odouratus, were found to elicit electroantennographic (EAG) responses from the antennae of female H. armigera. Compounds active in GC-EAG analyses of T. erecta floral headspace samples, identified by GC-MS and comparison of retention times on polar and non-polar GC columns with authentic standards, were (E)-myroxide, benzaldehyde, (f)-linalool, phenylacetaldehyde and (-)- piperitone. EAG-active compounds in L. odouratus floral headspace samples were identified as diacetone, (-)-linalool, phenylacetaldehdyde and benzyl alcohol. Increases in upwind flight to air entrained extracts of floral odours indicated that these cues caused attraction when presented to female H. armigera. A synthetic T. erecta blend comprising benzaldehyde, (f)- linalool, phenylacetaldehyde and (+)-limonene gave significant increases in upwind flight approaches. Limonene (either (+)- or (-)-) was found to be important for the behavioural response despite having low EAG-activity. There was no significant difference in upwind flight response to odours from the live flower and the synthetic floral blend. Significant increases in upwind flight were also obtained when insects were presented with a synthetic L. odouratus blend which contained the four EAG-active compounds identified from GCEAG studies. In field trapping experiments in Israel there was a significant difference in H. armigera catches in traps with a standard 4-component T. erecta lure compared with unbaited traps over the whole season. Mean H. armigera catch per trap per night (both sexes) over the whole season in unbaited traps, floral odour traps, pheromone traps and light traps were 0.004,0.11,8.8 and 1.35 respectively. The floral baited traps were non-selective catching large numbers of Ilymenoptera and Diptera as well as other moth species. Field trapping experiments in Pakistan indicated that the floral lure was significantly attractive to Earias spp. and other Lepidoptera although very few H. armigera were caught due to low population density. Olfactory cues are discussed in relation to host-plant finding behaviour of H. armigera. They are involved in early stages of host seeking behaviour prior to alighting on the plant and stimulate searching behaviour.

Since 1968 UK macro-moths have declined by 28%, with the most notable trends revealed for the south of England; the dual influences of climate change and intensive land use are thought to be the main drivers for this trend. This study aimed to determine the landscape and local-scale factors influencing moth abundance and species richness in intensive Northamptonshire farmland. The research consisted of four parts: 1. the analysis of historic county moth records using landscape-analysis, 2. Moth trapping in areas of intensive lowland farmland and subsequent local and fine-scale landscape-scale analysis of trap yields, 3. Moth movement studies along farmland hedgerows and 4. Moth visitation surveys of hedgerow flora. The results of the analysis of county moth records revealed that land-use statistics had a highly significant relationship with the abundance of moths across Northamptonshire. Woodland cover was found as having a positive relationship with the abundance of moths, but that urban cover was negatively associated. The farmland moth trapping study recorded a total of 121 species, the majority of which were generalist (98%) and none of which have Biodiversity Action Plans. For this trapping, hedgerow length, width and cross-sectional area, vegetative diversity and the numbers of hedgerow gaps all had an influence on the abundance of some of the species trapped, but no hedgerow or margin variables had a significant influence on overall abundance or species richness. Moth movement surveys found that a significant proportion of moths were travelling parallel along hedgerows (69% of moths observed at 1m from the hedgerow) in farmland and that moth activity was higher close to hedgerows. Nocturnal visitation surveys of hedgerow flora found that 53% of visitors were Lepidoptera and that the most visited species was Bramble (Rubus fruticosus agg.). The results of the combined studies suggest that land use influences moth abundance at a range of spatial scales and that hedgerows may be providing sheltered dispersal routes and nectar resources for these species.

A major challenge to evolutionary developmental biology is to understand the how modifications to gene regulatory networks can lead to biological diversity. Heliconius butterfly wing patterns provide an excellent example of this diversity. In particular, the species H. melpomene and H. erato display wide variation in wing pattern across their ranges in Central and South America, but wherever they co-occur, they have converged on remarkably similar wing patterns due to Müllerian mimicry. Linkage analysis of wing pattern genes has shown that in both species, there are three genomic loci that are responsible for most of the pattern variation, and that these loci are homologous. One locus, containing the transcription factor optix, is responsible for red pattern elements. A set of non-coding sequences linked to some of the red pattern elements have been identified. Another locus, containing the gene WntA, has been linked to the shape of the forewing band elements and is responsible for variation in wing pattern development in several species of lepidoptera. A third locus, responsible for yellow pattern elements, contains multiple candidate genes that may affect wing pattern development, including the gene cortex, which is also linked to the industrial melanism phenotype in the moth Biston betularia, as well as the genes domeless and washout, linked to the Bigeye mutant in Bicyclus anynana. I first investigated modifications to regulatory sequence near the transcription factor optix, detecting a module associated with the band pattern element. I also found that for some pattern regulatory modules at optix, the same sequence has independently evolved the same function in H. melpomene and H. erato, in association with non-coding sequences conserved throughout the Lepidoptera. I then investigated gene expression differences in two morphs from either side of a hybrid zone that vary only in the presence or absence of a yellow pattern element, in order to determine a role for candidate genes at the yellow pattern locus. In H. melpomene the gene cortex was upregulated in the larval wing discs of the black morph, whereas in H. erato it was upregulated in the larval wing discs of the yellow morph. In pupal wings, washout was differentially expressed, again in the opposite pattern in the two species, suggesting the same locus is responsible for convergent pattern modification, but by a different mechanism. Finally, I investigated the spatial transcriptomic landscape across the wings of three different heliconiine butterflies. I identified candidate factors for regulating the expression of wing patterning genes, including genes with a conserved expression profile in all three species, and others, including genes in the Wnt pathway, with markedly different profiles in each of the three species. Each of these studies contributes to our understanding of how gene regulatory networks can be modified to create diversity: first, at the level of cis-regulation, second at the level of gene interaction and expression, and lastly at the level of developmental bias and constraint.

Les pullulations de « papillon cendre » du genre Hylesia, appartenant à la famille des Saturniidae, constituent un problème récurrent de santé publique en Guyane et au Venezuela. En effet, pour protéger ses oeufs des prédateurs, la femelle possède des soies détachables extrêmement urticantes qu’elle est susceptible de libérer dans l’atmosphère. L’augmentation des sources de lumière artificielle depuis la fin du 19ème siècle liée à l’urbanisation croissante attire ces papillons nocturnes vers les villes et les villages, où la libération des soies urticantes est susceptible d’affecter l’Homme en générant une douloureuse affection de peau, la « papillonite ». Malgré les enjeux sociaux et économiques liés à la présence récurrente de ces papillons en zones urbaines, leur biologie et leur écologie reste peu connue. Les pullulations de « papillon cendre » attribuées à l’espèce H. metabus constituent un problème récurrent de santé publique en Guyane et au Venezuela. La définition de méthodes spécifiques de régulation des populations s’avère donc très urgente mais nécessitait au préalable de vérifier que seule l’espèce H. metabus est impliquée dans ces épisodes d’urtication et de préciser la structure des populations de ces insectes. Il était également important de préciser les mécanismes de reconnaissance des partenaires sexuels chez cette même espèce. Ces questions ont été les objectifs principaux de cette thèse. L’utilisation d’outils moléculaires a permis de montrer que seule l’espèce Hylesia metabus était impliquée dans les récents épisodes d’urtication en Guyane et au Venezuela. L’étude a également démontré que les populations guyanaises de cette espèce se distinguaient au plan génétique des populations du Vénézuela, et surtout qu’elles se structuraient en 2 sousensembles génétiques distincts entre la côte et l’intérieur de la Guyane. Tous les insectes collectés durant les épisodes de pullulation appartenaient au sous-ensemble côtier. Une approche basée sur l’étude du comportement de reproduction a été utilisée afin de préciser la temporalité d’émission de la phéromone sexuelle et ouvre de nouvelles perspectives pour l’identification de cette phéromone. / The genus Hylesia (Lepidoptera Saturniidae) are moths of human health importance in Venezula and French Guiana, inducing epidemic outbreaks of lepidopterism, a puriginous dermatitis caused by the urticating properties of the females’ abdominal setae. Adult female releases extremely urticating setae in the surrounding air, causing itchy dermatitis known as ‘papillonite’. Hylesia are attracted by artificial light source which are increasing since the end of the 19th century due to urbanization resulting in serious invasion event in towns and villages. Despite of the impact on human health, many aspects of the biology and their ecology remain unclear. The definition of specific methods of population regulation is thus very urgent but it was necessary first of all to verify that only the species H. metabus is involved in these episodes of urtication and to specify the population structure of these insects. It was also important to clarify the mechanisms for recognizing sexual partners in this same species. These questions were the mainobjectives of this thesis.The use of molecular tools has shown that a single species, Hylesia metabus, was involved in recent episodes ofurtication in Guyana and Venezuela. The study also demonstrated that the Guyanese populations of this species aregenetically distinct from the Venezuelan populations, and especially that they are structured in 2 distinct genetic subgroupsbetween the coast and the interior of French Guiana. All insects collected during outbreaks belonged to thecoastal subset. An approach based on the study of reproductive behavior has been used to clarify the temporality ofemission of the sex pheromone and opens new perspectives for the identification of this pheromone

No description available.

Heliconius butterflies exhibit Müllerian mimicry, in which two or more unpalatable species share a mutual advantage from having a common conspicuous colour pattern. These tropical butterflies have impressive visual signals, which are under conflicting selection pressures, as they are used in choosing potential mates and defending against visual predators through aposematic coloration. As both selection pressures are likely to be strong, different elements of the signal might be adapted for different receivers. Here, I combine sensory ecology with behavioural ecology to explain Heliconius colours signals of different co-mimic pairs. I explore how mimicry in Heliconius is perceived both from the perspective of predators and conspecifics, using visual abilities of both butterflies and birds. The different visual sensitivities of avian predators, H. erato females and males make them to perceive Heliconius coloration in different ways. My work suggests that having the ability to see in the ultra-violet light range enables higher discrimination between co-mimics both for birds and butterflies. Heliconius warning colours transmit a consistent signal across time of the day and habitat in a tropical forest for avian vision. In contrast through Heliconius vision there is evidence that patterns are more conspicuous in their own habitats. All these traits could facilitate communication between co-mimics and reduce the cost of confusion in courtship while still maintaining the advantages of Müllerian mimicry against predation. I conducted a field experiment to show that attack rates on a novel distasteful butterfly reduced over time, suggesting that Heliconius wing colouration can enhance aversion among predators. Finally, I have shown that Heliconius butterflies use leaf shape as a cue to approach their host plants, demonstrating the potential for Heliconius to drive negative frequency dependent selection on the leaf shape of their Passiflora host plants. Overall these results highlight ecological interactions between Heliconius butterflies, their predators and host plants.