Differential Aggression Responses Across
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Differen'al Aggression Responses across Instars and Host Plants of Epargyreus clarus C. Block, J. Lill Biology Department of the George Washington University Introduc'on Results Epargyreus clarus When poked, the caterpillars’ response was noted. Responses were categorized as being Host plants oNen vary in their nutri'onal value to part of five dis'nct categories: immobile, moving away from s'mulus, moving towards the organisms that eat them. The larvae of the s'mulus, bi'ng, or vomi'ng. The post-cool down test was actually a series of s'muli, but Silver-Spoed Skipper buerfly, Epargyreus clarus, there was not a significant desensi'zaon over the minute of repeated s'muli, so those is an insect that can be found on a wide variety of responses were each counted in the post-cool down responses. nave and invasive legume species, which offer a range of nutri'onal benefits that affect growth and PRE-COOL DOWN AGGRESSION RESPONSE POST-COOL DOWN AGGRESSION development. Moreover, the iden'ty of the host ON KUDZU RESPONSE ON KUDZU 100% 100% plant a par'cular caterpillar feeds on can influence 90% Vomit 90% Vomit 80% 80% its risk of mortality from its natural enemies 70% Bite 70% Bite 60% 60% (predators and parasitoids). Previous work with 50% Move Towards 50% Move Towards Photo by Yurika Alexander 40% 40% predatory insects has shown that diet can strongly 30% Move Away 30% Move Away 20% 20% influence levels of aggression (Grover et al. 2014) 10% Immobile % AGGRESSION RESPONSE 10% Immobile % OF AGGRESSION RESPONSES 0% 0% Future Direc'on 1 2 3 4 5 1 2 3 4 5 Preliminary studies of the defensive behaviors of E. INSTAR INSTAR Predator trials are being clarus caterpillars suggest wide variaon, ranging conducted to test what defensive from immobility to ac've bi'ng and vomi'ng. The PRE-COOL DOWN AGGRESSION RESPONSE POST-COOL DOWN AGGRESSION strategies are effec've against goal of this project is to explore the source(s) of ON WISTERIA RESPONSE ON WISTERIA 100% 100% different types of invertebrate this variaon, focusing on two likely candidates: 90% Vomit 90% Vomit 80% 80% predators, including two species the developmental stage of the caterpillar (early 70% Bite 70% Bite 60% 60% of paper wasp (Polistes dominulus vs. late instars) and the iden'ty of the host plant it 50% Move Towards 50% Move Towards 40% 40% and Polistes fuscatus) and the has been reared on. Host plant-mediated changes 30% Move Away 30% Move Away 20% 20% Chinese Man's (Tenodera 5 AGGRESSION RESPONSE in defensive behaviors are likely to be caused by 10% Immobile % AGGRESSION RESPONSE 10% Immobile 0% 0% sinensis). These trials are using a some combinaon of altered development and 1 2 3 4 5 1 2 3 4 5 INSTAR INSTAR variety of instars on all three host overall ‘vigor’. plants. Discussion Materials and Methods • Caterpillars on both host plants were much more ac've when responding to their Acknowledgements shelter being opened than repeated s'mulus aer the destruc'on of the shelter. Caterpillars are reared on kudzu and wisteria, with • Vomi'ng was a response that almost exclusively was used as a defense when the Thank you to John Lill, Mariana trials occurring either two or five 'mes a week. shelter was being opened. Only one individual vomited to defend against the repeated Abarca, Rachel Blankenship, s'mulus aer the destruc'on of the shelter. Michal Parak, Sarah Weinbrom, Trials are conducted first by opening the shelters • Kudzu caterpillars started vomi'ng at an earlier instar, but wisteria caterpillars started Maddie Maney, and Tara Scully. that the caterpillars build out of their host plant. u'lizing bi'ng as a defense before their kudzu counterparts. Funding was provided by the This act is considered the “Pre-Cool Down • Kudzu caterpillars were more likely to move away from the s'mulus as first instars, Harlan Fellowship, the GWU Response.” Caterpillars are then given five whereas caterpillars raised on wisteria were more likely to move towards the s'mulus Undergraduate Research Grant, minutes to cool down and then are poked with a as first instars. and the Washington Field wooden toothpick around every ten seconds for a • Immobility as a defense was most oNen used when caterpillars were second instars, Biologist Club. minute. both pre- and post-cool down. References and data are available upon request .