Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2008. / Title from PDF t.p. (viewed on Jul 27, 2009). Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6533. Advisers: Michael Wade; Curt Lively.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6534. Adviser: Sydney A. Cameron. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6535. Adviser: Sydney A. Cameron. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3285. Adviser: Lawrence M. Hanks. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0800. Advisers: Susan E. Fahrbach; Gene E. Robinson. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

In the absence of previous experience with flowers, how do bees distinguish between possible food sources and non-rewarding objects? Unrewarding stimuli (colours in Experiment 1 and patterns in Experiment 2) were presented in a radial arm maze. The unlearned approach responses of bumblebees (Bombus impatiens) were recorded and significant preferences were obtained: the bees chose yellow and blue over other colours, and radial patterns over concentric patterns or unpatterned discs. Habituation was demonstrated when choices proportions for the same pattern by the same bees decreased over two test sessions. When an attractive novel pattern was presented in the third session the trend was reversed. These data confirm both that truly naive bees have unlearned colour and pattern preferences and that learning not to approach these stimuli occurs in the absence of reward. Two further experiments tested the length of time that habituation is maintained by bumble bees and the degree to which contextual cues contribute to maintaining habituation. In Experiment 3 once bees habituated to a radial pattern response decrement was maintained after a stimulus presentation delay of two hours. After a 24 hour delay, however, the preference was restored. In Experiment 4 exposure to the context without stimulus presentation did not affect the retention of the habituated response. These findings confirm bumble bees' ability to habituate to a stimulus and delineate its time course as lasting in the range of minutes and hours but not days. They call into question the associative role of contextual cues in habituation for bumble bees.

The natural plant toxin asimicin and the standardized extract F020 from Asimina triloba (Annonaceae) were examined for their insecticidal properties using six insect species, encompassing four orders. Growth of Ostrinia nubilalis and Manduca sexta larvae was inhibited at 100 and 500 $\mu$g F020$\cdot$g diet$\sp{-1}$, respectively and mortality was significantly higher than controls at levels as low as 500 and 1 $\mu$g F020$\cdot$g diet$\sp{-1}$, respectively. Antifeedant properties were observed. Toxicity and growth reduction from exposure to F020 were apparent for Oncopeltus fasciatus (Hemiptera) and Tenebrio molitor (Coleoptera). Tenebrio molitor was significantly affected at doses as high as 250 $\mu$g F020$\cdot\mu$l$\sp{-1}$ and at 20 $\mu$g asimicin$\cdot\mu$l$\sp{-1}$. Examination of the effect of F020 on the respiratory rate of third instar O. nubilalis larvae demonstrated that F020 is an effective respiratory inhibitor. Both F020 and asimicin were very effective at inhibiting complex I, the NADH-ubiquinone site of the electron transport chain. The EC$\sb{50}$ values for inhibition of state 3 respiration by asimicin and F020 were 0.546 nmoles$\cdot$mg protein$\sp{-1}$ and 1.656 $\mu$g$\cdot$mg protein$\sp{-1}$, respectively. (Abstract shortened by UMI.)

Toxicokinetic and synergistic studies were conducted with dihydro-azadirachtin (H$\sb2$-AZA) and a tritiated tracer on the European corn borer (ECB), Ostrinia nubilalis Huber. Azadirachtin, a triterpenoid extracted from the Neem Tree Azadirachta indica A. Juss, has been recognized for years for its antifeedant and growth regulation properties on different insect species. The results have shown that: (1) H$\sb2$-AZA reduces the growth and affects the development of the ECB; (2) the elimination of the tracer within the feces takes between 12 to 24 hours following an oral or topical treatment; (3) the gut, the carcass and the fat bodies are subject to the highest accumulation of tracer for an oral treatment; the gut and the carcass present the highest accumulation of tracer for a topical treatment; (4) the penetration of tracer in the cuticle takes place rapidly, within the first 12 hours after topical treatment; and (5) dillapiol and piperonyl butoxyde, two polysubstrate monooxygenase (PSMO) inhibitors, increase the toxicity of H$\sb2$-AZA for the ECB. This study contributes to the understanding of how O. nubilalis reacts to the introduction of a substance like azadirachtin within its body and of how this molecule acts on the insect.

Based on the hydrolysis of synthetic substrates, pH optima for substrate hydrolysis and effects of potential activators and inhibitors, the identity and occurrence of cysteine proteinases in several major coleopteran families were investigated. The larval midgut of the Colorado potato beetle, Leptinotarsa decemlineata contains the cysteine proteinase cathepsin B and H, the aspartate proteinase cathepsin D and leucyl aminopeptidase. Cathepsin B and the serine proteinase trypsin were identified in the larval midgut of the yellow mealworm, Tenebrio molitor. Cathepsin B and the serine proteinase chymotrypsin were identified in the maize weevil, Sitophilus zeamais. The larger grain borer, Prostephanus truncatus, feeds on the same food source as S. zeamais but uses trypsin, chymotrypsin and leucyl and arginyl aminopeptidase and not cysteine proteinases for digestion. Trypsin, leucyl aminopeptidase and arginyl aminopeptidase and not cysteine proteinases were identified in a predacious carabid beetle, Pterostichus corvinus, a predacious tiger beetle, Cicindela sp. and a saprophagous hide beetle, Dermestes maculatus. (Abstract shortened by UMI.)

Many secondary plant compounds are capable of photoactivation resulting in the production of toxic species of oxygen. One mechanism of defense for insects feeding on phototoxic plants may be the presence of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPOX), and glutathione reductase (GR). The activities of these enzymes were examined in larvae of three lepidoptera: Ostrinia nubilalis, Manduca sexta, and Anaitis plagiata. Highest levels of antioxidant enzyme activity were found in A. plagiata, a specialist feeder on Hypericum perforatum, which contains high levels of the phototoxin hypericin. Larvae of A. plagiata fed leaf discs treated with hypericin exhibited a short-term, concentration-dependent decline in enzyme activity. Longer term studies with A. plagiata fed either the phototoxic H. perforatum, or the closely related but non phototoxic H. calycinum, resulted in increased CAT and GR activity in larvae fed the phototoxic plant whereas superoxide dismutase activity was not significantly different. These results suggest that CAT and GR may be inducible defenses against phototoxins. Other insect defenses against phototoxins include specific biochemical defenses such as antioxidants. These antioxidant defenses eliminate or quench the deleterious singlet oxygen and free radicals formed by these phototoxins. We examined the role of dietary antioxidants in protecting the phototoxin-sensitive insect herbivore M. sexta. Elevated dietary levels of the lipid-soluble antioxidants beta-carotene and vitamin E resulted in a concentration-dependent reduction in the mortality associated with treatment of larvae with the phototoxic thiophene $\alpha$-T. Elevated levels of dietary ascorbic acid had no effect whereas reduced levels greatly increased the toxicity of $\alpha$-T. Tissue levels of antioxidants were shown to increase substantially in larvae fed antioxidant-supplemented diets. The results suggest that the ability to absorb and utilize plant-derived antioxidants could be an important defense against photo-activated plant secondary compounds and may have allowed some insects to exploit phototoxic plants. The effects of oxidative stress induced by $\alpha$-T at the biochemical level and the protective effect of antioxidants and antioxidant enzymes were also examined. The phototoxin $\alpha$-T strongly induced lipid peroxidation (LPO) in midgut tissues of the phototoxin-sensitive M. sexta in a UV-dependent manner, however this LPO was prevented when the compound was administered to larvae raised on high vitamin E diets. In the absence of UV, $\alpha$-T caused a significant increase in GPOX, GR, and non-GSH-dependent PER activity over 72 h. However in the presence of UV, $\alpha$-T strongly inhibited GPOX and GR and prevented the increase in PER. $\alpha$-T also affected cellular thiol status with approximately a 50% increase in total and GSH content in midgut tissue, although this was not UV-dependent. The effectiveness of antioxidant enzymes and the antioxidant GSH in providing protection against phototoxins were also examined. Neither the SOD inhibitor DEDC nor the CAT inhibitor 3AT affected the acute toxicity of topically applied $\alpha$-T to M. sexta larvae. The GSH-depleting agent BSO also had no effect on acute toxicity. In contrast, GSH depletion strongly enhanced the chronic (72 h) toxicity of $\alpha$-T when the phototoxin was incorporated into diets. GSH depletion also enhanced LPO in midgut tissue of $\alpha$-T-treated larvae. Implications of the results are discussed in terms of the role antioxidants and antioxidant enzymes may have played in the successful adaptation of some insect species to phototoxin-containing plants. The interrelationships of biochemical, physiological, physical, and behavioural mechanisms of defense are considered.