J. HYM. RES. Vol. 9(2), 2000, pp. 220-240 The Natural History and Behavior of Hymenoepimecis argyraphaga (Hymenoptera: Ichneumonidae) a Parasitoid of Plesiometa argyra (Araneae: Tetragnathidae) William G. Eberhard Smithsonian Tropical Research Institute, and Escuela de Biologia, Universidad de Costa Rica, Ciudad Universitaria, Costa Rica Abstract. — Larvae of the koinobiont ectoparasitoid Hymenoepimecis argyraphaga Gauld used a series of different adaptations as they matured to hold onto the abdomen of their host spider, Plesiometa argyra, its web, and the larval cocoon: the first instar did not leave the egg chorion, which was glued to the spider by the female wasp when she oviposited; the second instar used two pairs of ventral abdominal protuberances to help hold onto both the first larva's molted cuticle and to what was probably a sheet of coagulated spider hemolymph that adhered to the larva and to wounds that it made on the spider's abdomen; the early final instar grasped the shed second instar cuticle that remained attached to the coagulated hemolymph with the ventral surface of its abdomen; and the late final instar used a row of mobile dorsal protuberances with sharply curved spines that grasped lines of a unique web that the larva induced the spider to spin just before killing it, and then the larva's own cocoon silk. The pupa used a pair of toothed protuberances at the tip of the abdomen to stay at the upper end of its cocoon. Other aspects of the wasp's biology that are described include infanticide by adult females; aculeate-like lack of use of the ovipositor to oviposit; manipulation of host web-spinning behavior, apparently by means of a fast-acting larval secretion with long-term effects; manipulation of host bleeding; alternative tactics in attacks on spiders; use of pheromones by females to attract males; cocoon spinning behavior; and a bias to parasitize female rather than male spiders. Although Ichneumonidae is undoubt-species resembles that of some European edly one of the largest of all animal fam-polysphinctines. It is an external koino-ilies, remarkably little is known about the biont on a spider, the tetragnathid Nephila behavior of the larvae. Excluding studies clavipes (L.). The female temporarily par-of foraging behavior, adult behavior is alyzes the host by stinging it in the ceph-also poorly studied (e.g., Hanson and alothorax, and then glues an egg on its ab-Gauld 1995). The neotropical polysphinc-domen. Spiders with a wasp egg or a tine pimplines are no exception. The more young larva are active, and build appar-derived polysphinctines are known to be ently normal prey capture webs and feed koinobiont ectoparasitoids of spiders while the larva feeds by sucking the spi-(Gauld 1995, Wahl and Gauld 1998), and der's hemolymph and gradually matures, several European species were observed The spider's webs become more irregular in careful detail by G. C. Bignell (1898) and reduced one to two days before the and E. Nielsen (1923, 1928, 1929, 1935). larva kills it and constructs its pupal co-There is apparently only a single study of coon, which is attached to the spider's a neotropical species, that of Fincke et al. web. A second species, H. tedfordi Gauld, (1990) on Hymenoepimecis robertsae Gauld parasitizes another tetragnathid spider, (for probable identification see Gauld etal. Leucauge marinae Keyserling (Gauld et al. 1998). The general natural history of this 1998), but nothing more is known about



The Natural History and Behavior of Hymenoepimecis argyraphaga (Hymenoptera: Ichneumonidae) a Parasitoid of Plesiometa argyra (Araneae: Tetragnathidae)

William G Eberhard
Journal of Hymenoptera Research 9: 220-240 (2000)

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