68 BULLETIN 1369, U. S. DEPARTMENT OF AGRICULTURE 
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 pupe 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 (62) records © 
an average pupal period of 32.9 days, the range being from 29 to 
40 days. In Ireland, Carpenter, Phibbs, and Slattery (29) 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 larve which drop normally a considerable percentage fail — 
to produce flies, even under what might be thought to be optimum — 
conditions. The percentage of the larve which pupate is rather | 
high. Among 559 larve of 4. lineatum which were noted at Dallas, 
Tex., 514, or 92 per cent, formed pupe and 337, or 65.6 per cent, | 
of the pupae emerged as adults, or 60.8 per cent of the total num- | 
ber. Both species of Hypoderma are very dependent upon proper 
conditions for completion of their development. Larvee 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 larve of H. lineatum 
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 larvee extracted and observed. All | 
of these larve had practically attained their full growth. | 
Among 221 larve of H. bovis 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 pupe. This | 
point will be discussed under natural control. 
EMERGENCE OF ADULT FROM PUPARIUM 
In the case of both H. lineatum and H. bovis 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. 4 
The cap of the puparium is first forced open by the head of the © 
fly, 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 
