Tachinid Fly Parasitism of Sphinx Larva

Description:

A large sphinx larva (Pachylia syces) (http://www.projectnoah.org/spottings/261...) was found in a park in the city of Oaxaca, Mexico (June 6, 2013) walking on the sidewalk, looking for a place to pupate. We brought it home, put it in some dry soil with leaf litter and it pupated that same day (June 8, 2013). We were happily expecting to see the adult sphinx (for pictures of the adult moth see: http://www.silkmoths.bizland.com/psycesy....) Unhappily for this moth, 10 large (1.2 cm), black, white-faced Tachinid flies emerged (4 on 26 July, 5 on 27 July and 1 more on 28 July 2013). There were 8 females and 2 males. In the first and second photos you can see the pupal cases of the flies bursting the seems of the sphinx pupa. The adult flies emerged through these sectional slits in the pupal case. The species of fly is Belvosia bicincta of the Family Tachinidae, a family of flies that parasitizes other insects as larvae. This sphinx was obviously parasitized some time during it’s development and the fly larvae watited until the sphinx larva was large, fat and pupated to begin their own development. After waiting several days, I dissected the pupal case of the sphinx. It was completely full of the pupal cases of the flies, as well as an addtional pupa which did not emerge (making a total of 11 parasites). There was only a tiny remnant of liquified sphinx tissue in the abdominal end of the pupa. While this type of parasitism is very unsettling, (and it arrouses sympathy for the poor moth), without Tachinid flies, the world might be overrun by caterpillars. This might be a first report of this fly parasitiing Pachylia syces in Mexico and in additon represents a massive multiple infestation not usually seen.

Habitat:

El Parque del LLano, Center of Oaxaca City. This park is especially populated with Jacaranda Trees.

Notes:

The flies took 48 to 50 days to emerge once the Sphinx larva pupated. This reference reports the parasitism of Pachylia syces in Brazil by this same fly species. However, not even a summary is available on line. Dias, M. M., 1976: Parasitism of Pachylia syces Lepidoptera, Sphingidae by Belvosia bicincta Diptera, Tachinidae, and a description of the larva and puparium of the parasite. Revista Brasileira de Entomologia 20(2): 83-90. See also: Belvosia bicincta (Diptera, Tachinidae) Parasitizing Larvae of the White-lined Sphinx Moth In Eastern New Mexico, US (http://biostor.org/reference/76920). In this latter case, only 1 fly emerged from each of the parasitized pupae (26% of 115 larvae collected). Belvosia bicincta has a large distribution from the southern United States south through Brazil and prefers the larvae of Sphingidae for parasitism.