34 
28j hours. One specimen which lived 23^ hours contained ovaries 
with only a small number of eggs, about 25 in each ovary. One 
adult which lived for 44 hours contained ovaries between the third 
and fourth stages, and showed the transition from stage 3 to 
stage 4 very clearly. Twelve adults contained ovaries filled with 
fully developed eggs (stage 4, PI. I, fig. 4), ranging in num- 
ber from 200 to 300. These adults lived from 30 to 67J hours. 
Two adults contained ovaries with eggs of stage 4. but in small 
numbers, about 50 in each ovary. They lived 48 and 56 hours, 
respectively, and possibly had developed the remainder of the eggs 
left within the ovary after a previous oviposition. One adult con- 
tained ovaries with eight fully developed eggs, and the remainder 
of the ovary filled with eggs corresponding to stage 3. This adult 
lived 34 hours and had presumably oviposited once, as is indicated 
by the presence of the eight fully developed eggs, and then devel- 
oped the remainder of the ovaries to stage 3. 
A comparative study of the ovaries of well-engorged (-j — | — \-) 
specimens shows that no adult which died before reaching a period 
of longevity of 30 hours after engorgement developed the eggs within 
the ovaries to full degree. On the other hand, with one exception, 
all adults which lived for 30 hours after engorgement developed the 
eggs within the ovaries to the fullest extent. The fully developed 
eggs within the ovaries were of the same shape as eggs freshly laid, 
and only a fraction smaller. 
THE APPARENT EFFECT OF A BLOOD MEAT LPON THE DEVELOPMENT OF THE OVAELES. 
In the studies which have been made of the ovaries of females of 
Simulium venustum under various conditions the following points 
are worthy of emphasis: (a) In all adults taken while oviposit- 
ing, apparently digested blood was found in the stomach, (h) Xo 
eggs within the ovaries developed to the fullest degree without en- 
gorgement and the requisite time in which to digest the blood meal. 
(c) The condition designated as stage 5 occurred both in adults 
which had just oviposited and also in adults which were taken on 
animals and killed at the time of capture. This condition (stage 5) 
seems to furnish strong evidence that adults feed again after oviposit- 
ing, as the majority of engorged adults showed the entire contents of 
the ovaries developed. In addition the exact cause of the similar 
condition found in adults which had just oviposited is known; 
namely, that a few fully developed eggs were left in the ovaries after 
oviposition and the remainder of the eggs were in a rudimentary 
condition apparently awaiting the necessary factors for development. 
(d) The males have reduced mouth parts and are not found engorg- 
ing on blood, indicating the acquisition of this habit by the females 
for a special purpose, as is the case with other blood-sucking Diptera. 
