Carotenoid Sequestration and Susceptibility to Natural Enemies

It has been shown that insect coloration is affected by diet, such as the sequestration of carotenoids obtained from the host plant.  This study was designed to examine any increase in survival rates that might occur as a result of carotenoid sequestration.  Trichoplusia ni Hübner larvae of various instars were used to conduct both indoor and outdoor trials. Larvae were reared on Brassica oleracea (winterbor kale), which provides carotenoids, or an artificial diet that did not.  Both groups of larvae were placed on B. oleracea plants to compare survival, both in open garden plots and in enclosed tents that contained the predator Podisus maculiventris.  Survival rates for those larvae sequestering carotenoids versus those that did not were measured and compared. Carotenoid sequestering larvae were found to have higher survival rates. In addition, we photographed larvae given 8, 16 and 24-hour intervals to sequester carotenoids, and compared their contrast to leaves as a measure of visual apparency to natural enemies.  Those larvae not sequestering had a higher contrast against the background of the leaf, making them more susceptible to being seen by predators. As predicted, we found that the ability to blend with the background as a result of sequestered pigments does afford the T. ni larvae an advantage against predation.