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CABBAGE BY NAME, KALE BY CHOICE: FEEDING PREFERENCE IN TRICHOPLUSIA NI

Abstract

The cabbage looper (Trichoplusia ni), as the name suggests, can feed on cabbage and related crucifers. However, previous studies show that T.ni fed a kale diet had increased larval weight, decreased larval stadia, and decreased mortality when compared to those fed cabbage. Given these life history differences, this study examines whether T. ni has a preference for feeding on cabbage or kale. To measure T.ni preference, 10mm cabbage and kale discs were placed around the edge of a 120mm dish in alternating order. Individually, first day 3rd instars (n=20) and first day 5th instars (n=20) were placed in the center of the dish. Initial food choice and the time it took for individuals to choose cabbage or kale was recorded. After 4hrs and 24hrs, pictures were taken and disc consumption was measured using Image J. Preference was determined by calculating percent of total kale consumed (kale consumed/total of kale and cabbage consumed). For both 3rd and 5th instars, kale was the preferred food source despite the fact that there was no initial preference for either cabbage or kale. For 3rd instars at 4hrs, the average percent of kale eaten is 86% and at 24hrs it is 95%. For 5th instars, at 4hrs the average percent kale consumed is 74% and at 24hrs is 56%. The 24hr time point for 5th instars indicates that if given enough time, T. ni will eat either food source even if it chooses to eat kale first. This highlights a preference and not an aversion to cabbage. Taken together, these results indicate a food preference behavior in T. ni that is possibly linked to later life history traits. Future studies will investigate the mechanisms driving this preference by determining which sensory cues T. ni is capable of detecting that indicate a nutritional difference between kale and cabbage.

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