﻿68 BULLETIN 1369, V. S. DEPARTMENT OF AGEICULTUBE 



the adult, the average for several being 34.7 days, and Glaser 

 (29) records this period as being 37 to 56 days in Germany. Under 

 just what conditions these pupse were kept is not known, but pre- 

 sumably they were out of doors. Vaney (106) in Lyons, France, 

 has observed that the period of transformation requires from 3 

 to 4 weeks. In the vicinity of Paris, France, Lucet (63) records 

 an average pupal period of 32.9 days, the range being from 29 to 

 40 days. In Ireland, Carpenter, Phibbs, and Slattery (19) record 

 a pupal period of 32 to 46 days. Stub {97), working in Copenhagen, 

 found the pupal period to be from 40 to 53 days. 



MORTALITY IN THE PREPUPAL AND PUPAL STAGES 



Among larvse which drop normally a considerable percentage fail 

 to produce flies, even under what might be thought to be optimum 

 conditions. The percentage of the larvae which pupate is rather 

 high. Among 559 larvse of H. lineatum, which were noted at Dallas, 

 Tex., 514, or 92 per cent, formed pupse and 337, or 65.6 per cent, 

 of the pupase emerged as adults, or 60.3 per cent of the total num- 

 ber. Both species of Hypoderma are very dependent upon proper 

 conditions for completion of their development. Larvae removed from 

 the backs of cattle before they are ready to emerge are subject to 

 a high percentage of mortality. It is conceivable that by forcing 

 them through the holes in the hide they may be injured, but the 

 writers' experience indicates that immaturity and not injury is the 

 cause of death. Among 325 well-developed larvae of H. Uneaticm 

 extracted by hand and kept under optimum conditions for pupation 

 and adult emergence, only 113, or 34.8 per cent, pupated, and out 

 of this number 26, or 23 per cent, produced adults. This was 8 per 

 cent of the total number of the larvae extracted and observed. All 

 of these larvae had practically attained their full growth. 



Among 221 larvae of H. hovis which emerged normally from hosts 

 and were kept in a screened insectary in Middletown, N. Y., 186, 

 or 84 per cent, produced adults. 



Excessive moisture produces a high mortality among pupae. This 

 point will be discussed under natural control. 



EMERGENCE OF ADULT FROM PUPARIUM 



In the case of both H. lineMnmn and H. hovis the flies appear 

 mature within the puparia several hours before they emerge. The 

 majority of the adults reared by the writers have been found to 

 escape from the puparia during the early morning hours. 



The; cap of the puparium is first forced open by the head of the 

 Ay, and in some cases it is broken off completely. The fly then 

 crawls out, and this process takes less than half a minute. Within 

 a few minutes after the fly escapes it usually walks away from the 

 puparium and begins to unfold its wings. Usually this process re- 

 quires about five mintues. The ptilinum is completely retracted and 

 the wings straightened to normal position in about 15 minutes after 

 emergence. The abdomen is conspicuously distended, showing 

 that the insect is provided with an ample supply of food from 

 the larval stage. An occasional droplet of excrement is voided 

 during the drying process. Immediately after the wings are dried 



