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a THE CATTLE GRUBS OR OX WARBLES 69 
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the abdomen is extended and retracted and the insect makes clumsy 
attempts at flight. Within half an hour after emergence it is able 
to sustain itself on wing, though rather clumsily. 
The adults evince a very strong positive heliotropism. In cap- 
tivity their main energies are devoted toward escaping. Very 
_ few flies have been recovered in nature unless in the act of attack- 
ing cattle, and just what place they choose for resting is not known. 
Apparently, however, they remain on the ground or on grass and 
‘shrubbery close to the ground. 
PROPORTION OF SEXES 
| The sexes were noted in the case of 284 reared adults of 7. 
lineatum. Of these, 147, or 51.8 per cent, were males. The males 
usually emerge from the puparia slightly before the females, al- 
though this is not uniformly the case. Among 172 adults of ZH. 
bovis which were reared and the sex noted, 81, or 47.1 per cent, 
were males. 
FOOD OF THE ADULT 
Mention has been made of the supply of food carried over to 
the adult stage from the larve. This appears to be sufficient to 
meet the needs of the adult insect throughout its hfe. The writers 
have repeatedly attempted to feed reared adults in captivity on 
fruit, sirup, and water, but have never observed any indication that 
they would partake of such substances. The mouthparts are de- 
generate and probably not capable of functioning in feeding. 
MATING 
Many reared flies of /7. lineatum have been kept in various types 
of breeding cages, usually supplied with sticks or branches of green 
trees, and in the much greater number of these cases mating was 
not observed to take place. Although a number of these reared 
females were induced to oviposit, in most instances the eggs were 
infertile. In four cases mating was closely observed. The act 
usually took place immediately after the males and females were 
placed in the same small cage. In each instance the male seized the 
female as soon as they met, but in one case the male went through 
some preliminary courting actions. He crawled over the female’s 
back and head, then worked rearward on the back of the female and 
mating began. The details of mating appear to be about the same 
as with many other Diptera. The duration of the act ranges from 
one to three minutes. In two instances mating was repeated a second 
time immedistely after the first. In two of the four instances of mat- 
ing observed in /Z. lineatum. both the male and female were 1 day 
or more old. In the other instance, however, which occurred at 
10.45 a. m., the male had emerged shortly prior to 9. a. m. of the 
same day, and the female was observed to crawl from the puparium 
at 10 a. m.; thus mating took place when the female had been out 
only 45 minutes. It is interesting to note in this connection that 
this female upon being placed on a calf 20 minutes after mating 
deposited a considerable number of fertile eggs. : 
HT, bovis evidently mates much more freely in captivity than 
Hl, lineatum. The act has been observed in many instances to take 
