Leaf selection and daily variation on feeding and oviposition of Gratiana spadicea (Klug) (Coleoptera, Chrysomelidae, Cassidinae)

Abstract

Gratiana spadicea

(Klug) (Coleoptera, Chrysomelidae) is a monophagous beetle that feeds only on leaves of Solanum sisymbriifolium Lamarck (Solanaceae). We determined the portions of S. sisymbriifolium leaves that are used by the adults as feeding and oviposition sites. Daily variation on larval and adult feeding frequency, and on oviposition, was also registered under laboratory conditions (25oC; 70+10% rh). Larvae and adults were fed with S. sisymbriifolium leaves during photo (14 hours) and scotophase (10 hours). At the end of each phase, it was measured the leaf area they ate and registered position of their feeding marks on leaves. The oothecae were counted and noted, regarding their position on the leaf blade. Larvae and adults of G. spadicea showed feeding activity during photo and scotophase. Oviposition was restricted to photophase. Females leaf consumption rates were greater than those of the males. Adult feeding marks were most frequent on leaf margins. Oothecae were most frequently found near the central vein of the abaxial leaf surface. Daily ingestion rates grew exponentially through the larval stage; fifth instar ingested more than 60% of the total amount of food consumed by the larval stage. The possible adaptive mechanisms involved in such feeding and oviposition patterns are discussed.