Natural History and Leaf Shelter Construction of the Asian Rice Leptispa Beetle Leptispa pygmaea Baly (Coleoptera: Chrysomelidae: Cassidinae: Leptispini)

Abstract

Kaniyarikkal Divakaran Prathapan, Caroline S. Chaboo, and Kolandaivelu Karthikeyan (2009) Natural history and leaf shelter construction of the Asian rice leptispa beetle, Leptispa pygmaea Baly (Coleoptera: Chrysomelidae: Cassidinae: Leptispini). Zoological Studies 48(5): 625-631. The leaf-roll construction by the Asian rice leptispa beetle Leptispa pygmaea Baly (Cassidinae: Leptispini) was studied. Consistent adult feeding on the adaxial side of tender rice leaves Oryza sativa Linnaeus (Poaceae) induces partial upward rolling of the leaf lamina. Adult leaf rolls are ephemeral and not apparent, and they unfurl once the beetle leaves the leaf. Females oviposit clutches of up to 8 eggs mostly on the adaxial side of the leaf within such rolls. Neonate larvae migrate to the base of the leaf axil and feed by scraping, which induces formation of leaf rolls from the base where the leaf is already curled up. All 5 larval instars feed in this manner, migrating to new leaves and forming new leaf rolls. Pupation occurs within the leaf roll of the 5th instar. Adult leaf rolls are partial and ephemeral, and therefore offer only limited protection to eggs and adults. In contrast, larval leaf rolls are well formed and cohesive compared to those of adults. This is probably due to the sedentary nature and active feeding of the larvae resulting in a greater reduction in leaf turgidity. The host plant, leaf curling, and leaf-roll architecture of Leptispa Baly differ from the leaf ‘sandwiches’ built by some Neotropical cassidines, of the Imatidiini, that glue together Inga leaves (Fabaceae). Two terms, leaf rolls for Leptispini and leaf case shelters for Imatidiini, are proposed to reflect the lack of homology of these structures, although both function as shelters. We also propose that Leptispa feeding probably induces loss of turgor pressure that in turn induces inward curling of the leaf to produce an elongated leaf roll. This may be regarded as an ideal example of cost-effective shelter building by an insect. http://zoolstud.sinica.edu.tw/Journals/48.5/625.pdf