Caterpillar bioassays

Gypsy Moth and Forest Tent Caterpillar Bioassays... 

The statistical analyses of the data concerning the four caterpillar bioassays involves an analysis of variance (ANOVA) for a completely randomized design (CRD) followed by Dunnett s test for each experiment. The ANOVA are done to get a preliminary feel if the treatments had any effect on the test organism. Dunnett s method is chosen because we are interested in determining whether the mean of the control group is significantly different than each of the means of the treatments. Experimental treatments can consist of crude extracts or pure compounds. 

Youngsteadt and DeVries (2005) described the putative role of chemical mimicry in a lycaenid caterpillar (Lepidoptera Lycaenidae), i.e., the harvester Feniseca tarquinius, that preys on some ant-tended Homoptera (see Aphid section). Chemical analyses and behavioral bioassays indicated that aphid-like camouflage allowed the caterpillar to evade detection by the ants (genera Camponotus or Formica) without other concealment behavior. The authors stated that mimicry was not an active process in this case. 

To investigate food preferences by insects or other herbivores, such as deer (Rautio et al. 2008), and the compounds responsible for their choices, these compounds can be added to their diet and tested in feeding bioassays. Here we will add a mixture of phenolic compounds, known as tannic acid, to the diet of homworm caterpillars. The tobacco homworm, Manduca sexta, normally feeds on Solanaceae such as tomato or potato plants. For more on the natural history of this insect, consult the information sheet prepared by the biological supply company that ships these caterpillars. 

We will perform one of the two bioassays dealing with tannins in insect diet The compounds to be tested (tannic acid) are mixed into diet in varying concentrations. We measure how much chow the caterpillar has consumed and whether the effect is concentration dependent. (The second bioassay - in Chap. 19 - employs the Leaf disk lest. In this often used bioassay leaf sections of a standard size are treated with the compounds in question.)... 

We will perform the Leaf disk test, also known as leaf disk assay or leaf disk choice test, the second of two bioassays of tannins in the diet of insects in this book. In this often used bioassay, leaf sections of a standard size are treated with the compound(s) in question. Several circular leaf sections ( leaf disks ) (Ali et al. 1999, Filho and Mazzafera 2000, Shields et al. 2008, Wheeler and Isman 2000) or cellulose membrane filters (Hollister and Mullin 1999, Larocque et al. 1999) are presented to a caterpillar in a choice experiment. We measure how much chow the caterpillar has consumed and whether any feeding inhibition is concentration dependent. Regardless of what compounds are being tested, leaf disk tests serve as an important tool in bioassaying feeding inhibitors and stimulants in insects. The cited references are examples of such studies. (In the first tannic acid experiment - Chap. 18 - the tannic acid was mixed into diet in varying concentrations.)... 

Ignoffo CM, Boucias DB. Relative activity of geographical isolates of Nomuraea bioassayed against the cabbage looper and velvetbean caterpillar. J Invertbr Pathol 59 215-217, 1992. 

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