Foliage Type and Deprivation Alters the Movement Behavior of Late Instar European Gypsy Moth Lymantria dispar (Lepidoptera: Erebidae)

Abstract

The movement behavior of insects characterizes their ability to disperse, establish, compete, forage, seek mates, and ultimately reproduce. Understanding the movement of invasive insects is particularly important for developing management policies. We conducted laboratory experiments in Minnesota, USA to determine how host type and food deprivation affected the movement of late instars of the European gypsy moth Lymantria dispar (Lepidoptera: Erebidae), an invasive forest insect in North America. Gypsy moth larvae can feed on over 300 species of trees and shrubs. During outbreaks food availability to conspecifics can become severely restricted as developing instars consume increasing amounts of foliage. Larvae were raised on one of five foods: Quercus macrocarpa, Larix laricina, Acer platanoides, Acer saccharinum, or artificial diet. Subsets of fifth and sixth instar larvae were also deprived of food for zero, 24, or 48 h. After the food deprivation period, late instar larvae were placed on a servosphere and their movement paths were recorded. Larvae raised on Q. macrocarpa, a preferred host, were unlikely to move unless starved. They moved farther the longer they were starved. In contrast, when larvae were raised on less preferred hosts, they were more likely to move without prior starvation. These results suggest that feeding on optimal hosts provides gypsy moth larvae with the energy and nutritional requirements to move more quickly to more food when there is none immediately available.