264 Journal New York Entomological Society. t VoL xxvil. 



at the ends facing up and down stream. Under this covering the life 

 of the pupa is spent. 



In 1914, when the previous article was written, it was not under- 

 stood how the pupa, with its four tubular spiracles and absence of 

 gills, could respire beneath the surface of the water. Later experi- 

 ments, however, show that though the pupa is beneath the surface 

 of the water, its back at least, on which the spiracles are located, 

 is surrounded by air. 



To determine whether the pupa cases contained air or water, 

 stones on which they were attached were slid beneath the surface 

 of the creek to a locality where the water was quiet. Here the 

 cases were pulled loose from the rocks, and each one was found to 

 contain a bubble of air, which had collected beneath the roof of the 

 pupal case in the well aerated water of the riffles. 



The necessity for this air explains the death in our breeding cages 

 of more than fifty pupse in their cases which had been removed from 

 the rocks, though almost every one that was left on the rocks sur- 

 vived till maturity. 



Ginglymia acrirostris. 



Of more than one hundred specimens of Elophila collected in 

 Fall Creek in August at least fifty per cent, were parasitized by 

 Ginglymia acrirostris, a Tachinid fly. The infested specimens con- 

 tained the withered remains of the lepidopterous larvae and the puparia 

 of the parasite, a single puparium to a larva. The silken pupal cases 

 of the infested hosts seemed perfectly normal. 



In form the puparium, fig. 3, is oval, 5 mm. long and 2 mm. wide. 

 Its color is amber brown. On the dorsal surface it has two con- 

 spicuous eye-like spiracles connected by a U-like structure which 

 points away from the head. The U connecting the spiracles repre- 

 sents respiratory tubes of the last larval instar. It penetrates the 

 puparium through a single circular opening at its base. Behind the 

 circular opening where the respiratory tubes penetrate the puparium 

 there is a small, heavily chitinized circle, whose function is at yet 

 unknown. 



A single larva of Elophila was found in the prepupal instar which 

 contained the parasite, evidently in the last instar. In this specimen, 

 fig. 4, the back of the larva on the suture between the fourth and fifth 



