<p>A study of the tarsi and mouthparts of females in three representative genera of tabanids revealed that the ventro-lateral surface of the fore-tarsi and the aboral margin of the labella were the principal loci of contact chemical sensilla. Of the four main types of aboral labellar trichodes (A,B,C and D), two (B and C) proved to be gustatory and then only at the tip. Two other types of trichodes (E and F) were identified on the anterior aspect of the labella. These were different from the aboral setae (type A,B,C, and D) in shape, size and function. </p><p>Extension of the proboscis was taken as the index of positive tarsal stimulation and the criterion of positive labellar stimulation was the spreading of the labellar lobes in an extended proboscis. This was observed to be the same in free as well as attached experimental flies. Newly emerged females showed similar response.</p><p>The frequency method generally employed in psycho-physical studies for estimating thresholds in mammals was successfully extended to tabanids. Using this method the stimulative effectiveness and threshold of various sugars for the tarsal and labellar taste sensilla was determined. Comparison was made between the frequency method and the ascending method of estimating thresholds with regard to sucrose. The effect of starvation on responsiveness of tarsal and labellar contact chemoreceptors was determined. Newly emerged flies became increasingly sensitive to sucrose during the duration of tests when they were strictly maintained on water diet. </p><p>Intergenerlc differences and similarities were seen in the behaviour immediately before feeding. The flies fed on "dry" sucrose as well as on solutions of appropriate concentrations. By analysing the crop contents of wild-caught tabanids, it was established that they fed on sugars and these findings were related to tabanid feeding behaviour and adaptation in nature.</p><p>Using whole blood, sugars and blood-sugar mixtures at various concentrations and proportions (in the case of blood-sugar mixtures), their dispatch to crop and/or mid-gut was studied. In addition, select group of amino acids and nucleotides were also tested to determine if these acted as feeding stimulants for the deer-flies.</p><p>Wild-caught females of deer-flies lived on dry sucrose and water and on 1.OH glucose solution longer than on distilled water alone or without food and water.</p> / Thesis / Doctor of Philosophy (PhD)

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In the honey bee, responsiveness to sucrose correlates with many behavioural parameters such as age of first foraging, foraging role and learning. Sucrose responsiveness can be measured using the proboscis extension response (PER) by applying sucrose solutions of increasing concentrations to the antenna of a bee. We tested whether the biogenic amines octopamine, tyramine and dopamine, and the dopamine receptor agonist 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN) can modulate sucrose responsiveness. The compounds were either injected into the thorax or fed in sucrose solution to compare different methods of application. Injection and feeding of tyramine or octopamine significantly increased sucrose responsiveness. Dopamine decreased sucrose responsiveness when injected into the thorax. Feeding of dopamine had no effect. Injection of 6,7-ADTN into the thorax and feeding of 6,7-ADTN reduced sucrose responsiveness significantly. These data demonstrate that sucrose responsiveness in honey bees can be modulated by biogenic amines, which has far reaching consequences for other types of behaviour in this insect. (C) 2002 Elsevier Science B.V. All rights reserved.

The honeybee is one of the model species in insect olfaction and its sense of smell is well studied. However, knowledge about the spectrum of odorants detectable to honeybees is limited. One class of odorants that has never been tested so far are the amino acids, which are important constituents of floral nectar. The experiments reported here were conducted in order to (1) determine if the odor of amino acids is detectable to honeybees (Apis mellifera), and (2) determine olfactory detection thresholds in honeybees for detectable amino acid odors. To this end, the proboscis extension reflex, a classical conditioning paradigm that takes advantage of the honeybee’s ability to build a robust association between an odor stimulus and a nectar reward, was used. The results demonstrate that five out of 20 amino acids presented at 100 mM were detectable. The honeybees’ median olfactory detection thresholds for these five amino acids are 12 mM for L-tyrosine and L-cysteine, 50 mM for L-asparagine and L-tryptophan, and 100 mM for L-proline. These threshold values are high in comparison to naturally occurring concentrations in floral nectar, and compared to threshold values obtained in vertebrate species. One possible explanation for these findings is that the size of the olfactory receptor repertoire of honeybees limits their olfactory capabilities in terms of detectability and sensitivity for the odor of amino acids

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Argulus foliaceus (Linnaeus, 1758) is a member of the branchiuran family Argulidae and has a worldwide distribution, causing major economic impacts for freshwater aquacultured fish species worldwide. In the UK, it has economic impacts for both aquaculture and sports fishing industries. Previous studies observed haemorrhagic and inflammatory responses after Argulus infection, which has been taken to support the idea that the parasite secretes chemicals during the feeding process to assist with the ingestion of blood and epithelial tissue. The present study suggests that the blood-feeding ectoparasite of fish, A. foliaceus, may use similar mechanisms for evading host immune responses to those used by sea lice and other haematophagous arthropods. No previous studies have directly investigated the nature of the bioactive compounds / proteins, assumed to be released from these ectoparasites, and which are considered to contribute to feeding processes and host-parasite interactions during infection. Thus, the work described in this thesis was undertaken with the objective of identifying, describing and characterising the secretory components that have previously been suggested to be secreted from glandular cells associated with the feeding appendages of Argulus foliaceus. The current study applied transcriptomic and proteomic techniques in conjunction with in situ methods to investigate known immunomodulatory genes that may serve a function in parasite-host interactions. Overall, the findings of this project have generated considerable additional knowledge concerning the biology of Argulus spp. and have provided a list of proteins that may be used by the parasite to facilitate feeding processes by secreting these active molecules into the host and hence modulating their immune defence mechanisms. This information can be used as a baseline for developing freshwater lice control strategies to help prevent the spread of Argulosis in aquaculture by applying vaccination as means of control using the candidate antigens described in this study to specifically target Argulus spp. Knowledge generated by the work described in this thesis can also contribute to the development of drugs for controlling Argulus or functional components of feed that may serve to protect fish against this parasite. Furthermore, data from this thesis enhances the knowledge of the distribution of toxin/venom or venom-like substances in crustaceans and arthropods in general.

In this study, the effects of the neonicotinoid pesticide, thiamethoxam, are examined through the Proboscis Extension Response (PER) in honey bees (Apis mellifera). PER is a form of classical conditioning applied to honey bees through scent and reward association which quantifies learning rates. Results between groups treated with thiamethoxam did not differ significantly from untreated control groups. Potential reasons for these results are discussed. The method and experimental apparatus for testing the PER assay are also discussed.