Eur. J. Entomol. 106 (3): 353-356, 2009 | 10.14411/eje.2009.043

Investment in cocoon-silk and structure of the clusters of cocoons produced by gregarious microgastrine wasps (Hymenoptera: Braconidae)

Jun TAGAWA1, Yoshibumi SATO2
1 Department of Biosphere-Geosphere System Science, Faculty of Informatics, Okayama University of Science, Okayama 700-0005, Japan; e-mail: tagawa@big.ous.ac.jp
2 Kyoto College of Medical Science, Sonobe, Nantan, Kyoto 622-0041, Japan; e-mail: sato@kyoto-msc.jp

After leaving their hosts, the larvae of endoparasitic braconid wasps pupate in cocoons. To determine their investment in cocoon silk, the dry weight of newly emerged wasps and that of the empty cocoons were measured for three gregarious braconid species of slightly different sizes: Glyptapanteles liparidis (Bouché), Cotesia glomerata (L.) and Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae, Microgastrinae). These braconids form clusters of cocoons of different types. Glyptapanteles liparidis is significantly larger than either of the Cotesia species, and C. kariyai is the smallest. The ratio of the weight of cocoon silk to the total weight of cocoon silk, wasp body, cast cuticle and meconium is smaller for small species than large species. Small species economise on their use of silk by aggregating cocoons and can therefore invest a larger fraction of their resources in adult body mass. Moreover, the larvae of the smallest species, C. kariyai, additionally reduce their use of silk by constructing a communal airy silk layer beneath which the individual cocoons are formed.

Keywords: Braconidae, Microgastrinae, Glyptapanteles liparidis, Cotesia glomerata, Cotesia kariyai, cocoon, cocoon cluster, body size, silk investment, aggregation

Received: December 17, 2008; Accepted: April 20, 2009; Published: July 24, 2009

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