Manifestations of a pupal diapause in two species of flies,Sarcophaga argyrostoma and S. bullata

Sarcophaga argyrostoma shows under certain conditions a state of arrested development, recognized as a diapause, in the pupa shortly after the head has become evaginated and before the antennae of the adult fly become visible, i.e. about 40 hr after formation of the puparium. Diapause occurs in: (1) Cultures raised and maintained at 13·5°C and (2) cultures raised at 18°C under conditions of short days—8 hr light/16 hr darkness (LD 8 : 16). Diapause also arises when larvae are raised at higher temperatures and the prepupae or young pupae transferred to 13·5°C. Diapause does not ensue from transference from 23 to 18°C, LD 8 : 16. In both cases of diapause development starts spontaneously after 6 to 12 months. Upon transference to higher temperatures development in the 13·5°C diapause starts almost immediately, whereas in the 18°C, LD 8 : 16 diapause it starts only after a delay the length of which depends on the temperatures employed. The 18°C, LD 8 : 16 diapause is also shortened by chilling at 6°C for 1 to 2 months. The diapause in S. bullata is manifested in exactly the same morphological state as in S. argyrostoma, but differs from it in that it has so far not been induced by short days, and in the 13·5°C diapause is terminated spontaneously after shorter periods. In certain instances arrested development occurred in the state when the antennae are just visible.