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Influence of Host Plants on the Immunology of Fall Webworm

The generalist insect herbivore fall webworm (Hyphantria cunea) is a moth species found in Colorado, and its larvae (caterpillars) have been found to have considerable variance in their performance (survival, number of offspring) when reared on different host plants. While it is known that the fall webworm is a generalist herbivore, it is not known how feeding on different host plants can affect the immune function of fall webworm larvae. This experiment investigated if the fall webworm immune system is affected by larvae being reared on different host plants that vary in quality. Fall webworm larvae were reared from 10 maternal lines on 4 different host plants with 2 of the plants being higher quality and the other 2 plants being lower quality. When the larvae reached their 4th instar, their hemolymph was examined to obtain the number of hemocytes, specialized immune cells. Filaments were then inserted into the larvae to measure melanization. Melanization occurs when an insect is immune challenged by a foreign entity, and its immune cells encapsulate the entity with layers of hemocytes. The filaments were extracted 24 hours later and analyzed using a computer software program. This experiment is ongoing, and the data is currently being analyzed. This project will help to understand if variation in host plant species causes varied immune response in fall webworm.

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