450 



Journal of Agricultural Research 



Vol. XV, N«. 8 



even within a few days after the larva hatches. No cannibalism occurs 

 among the larvae of this parasite although from 20 to 30 individuals 

 may be developing simultaneously. In such congested cases they nearly 

 all mature, but result in dwarfed adults. No waste matter is passed 

 by the larva, the midintestine being closed caudally during the entire 

 period of larval development. The larva enters a short prepupal period, 

 from 2 to 3 days in duration, before pupating. During this prepupal 

 period a very small portion of the accumulated waste is voided. This 

 would indicate that the mesenteron and proctodeum become connected 



even before the pupa is actually formed. No 

 hibernating form of the larva is known to 

 occur. 



The pupa is formed with its head facing the 

 cephalic end of the puparium (fig. 32). In 

 cases where 20 or 30 pupae are packed within 

 the puparium, a few may lie with the position 

 reversed. Of 200 puparia containing pupae 

 of T. giffardianus , examined during August 

 and September, 191 7, 3 per cent of the pupae 

 were lying with the head in this reversed 

 position. 



The duration of the combined egg, larva, 

 and pupa stages is from 24 to 31 days in 

 the cool months and lasts about 18 days dur- 

 ing the warm months. In January, 191 7, 243 

 adults emerged in from 24 to 31 days after 

 the eggs were deposited, with an average 

 period of 28 days. In April, 1917, 894 adults 

 emerged in from 19 to 26 days after the eggs 

 were deposited, with an average period of 21 days, and in July, 1917, 

 455 adults emerged in from 17 to 19 days after the eggs were deposited. 



Fig. 32. — Tetrastichus giffardianus: 

 Pupae in normal position and 

 number in fruit -fly puparium 

 opened to show contents. Greatly 

 enlarged. 



The adult emerges from the puparium by gnawing a small hole, more 

 or less ragged and circular. Though the puparium may contain from 

 3 to 30 parasites, usually only one emergence hole is made. The typical 

 position of the emergence opening is shown in figure 33. Occasionally 

 two holes are made, and rarely three. They may be at either end of 

 the puparium or between the extremities. More than one emergence 

 hole usually results from the development of an excessive number of 

 individuals in the puparium. In one rare case wherein 39 parasites 

 emerged from a single puparium, three emergence holes were made. 

 A distinct, thin, brownish pupal skin is left in the puparium after the 

 adult has issued. Although wrinkled and twisted, the skin is an exact 

 replica of the mature pupa. The parasites may twist and turn about 



