The larva of Pelecinus polyturator (Drury) (Hymenoptera: Pelecinidae)

Norman F. Johnson, Luciana Musetti, James B. Johnson, and Kerry Katovich

Proceedings of the Washinton Entomological Society 101 (1), 1999, pp. 64-68.

The application of characters from larval morphology to the study of relationships within the Hymenoptera is very uneven. There are some good examples of the usefulness of immatures as an additional source of data (e.g., Evans 1987), but for many superfamilies little or nothing is known. Progress in this area is hindered for several reasons. Most Apocrita are parasitoids of other insects, and the hosts for a number of groups are very poorly known. Many species are internal parasitoids; thus it is difficult to obtain early instars and often the larvae are highly simplified in structure.
Within the Hymenoptera a remarkable array of larval body plans is found. Clausen (1940) outlined fourteen types among the parasitic Hymenoptera alone. Some of these are highly simplified, "embryonic," forms, while others possess well-developed, exaggerated mandibles and caudal appendages. Later instars usually converge upon a generalized, hymenopteriform type. Little phylogenetic pattern has been found amidst this variety; at present we are confronted with a diversity of forms without any underlying organizing principle.
The superfamily Proctotrupoidea s. str. is comprised of ten extant families of internal parasitoids. The hosts for three of these (Renyxidae, Austroniidae, and Peradeniidae) are unknown, and only a bare minimum of information is available for the Monomachidae and Roproniidae. The only families for which immature stages have been described are the Diapriidae (a large group of nearly 2,000 recognized species), Proctotrupidae (331 described species), and Heloridae (a relict group of 10 extant species). In total, the larvae of only six species from this complex have been described. We report on the larvae of the Pelecinidae, a small group (only one species currently recognized) of uncertain affinities (Rasnitsyn 1980, Dowton et al. 1997).

Pelecinus polyturator, larva. Head of first instar in lateral view.