DIPTERA. 129 
My observations have been mainly concerned with the practical side of the sub- 
ject, and not until the past year or two have I taken much trouble to investigate 
the life history of the insect. 
As a rule, the fly begins its work in June, but nothing like vigorous business activ- 
ity is reached until July, when for three or four months the time of the stockman 1s 
kept constantly absorbed in attending to animals with ‘‘ wormy’’ sores. This year 
(1888) the most trouble was experienced during September and October, and out of 
some 200 head of cattle and 60 or 70 head of hogs we had as many as 15 or 20 cases 
under treatment in a space of less than two weeks. 
The trouble starts usually by some little scratch, perhaps caused by barbed wire 
' or by a stroke from a horn; sometimes, frequently in fact, it starts by an undue 
accumulation of ticks and consequent rubbing of the animal, which, while removing 
some of the ticks, leaves an opening in the skin through which a little blood will 
exude. In either case the basis of the operation seems to be a raw or slightly bloody 
surface, and the rapidity with which the work is carried on is wonderful. The eggs 
are deposited and the larve appear in a very short time; from what I have noticed I 
should say in less than thirty-six hours after the egg is deposited. 
I have been told, time and again, by those who assume to know, that the ‘‘screw- 
worm fly” does not deposit the eggs—that they are hatched within the body and the 
young larva deposited after hatching. There is a gray fly which does this, but the 
female deposits only a few larvz, and they are not by any means to be dreaded so 
much as the green fly (brown head), which deposits eggs by the wholesale. 
I have never seen a ‘‘screw-worm” (larva) which I could trace directly to a gray 
fly. All of the worms which I have bottled up and hatched under positive guard 
against error have turned into the same kind of fly, specimens of which (in alcohol) 
are herewith transmitted for your examination. 
It is said, however, that the gray fly works earlier in the season. This may be true, 
as the flies I have hatched out have been from worms taken from sores during 
September and October. 
In October of this year a house cat which I have had his foot injured, presumably 
by fighting. When we next saw him, about three days later, his foot was swollen 
and filled with screw-worms. We took out over 60 screw-worms from his foot within 
six days. All of these were placed in a bottle with a little earth and covered by a 
wire screen. 
The worms pupated and transformed in twelve days, about 30 flies coming out; all 
like the flies sent you. 
During the few days that the worms were in the cat’s foot they divested the bone 
of almost every particle of flesh and caused one of the phalangeal bones to come out 
entire. 
About a week after this I bought a thoroughbred Hereford calf and had him 
shipped down from the northern part of the State. On arrival I found screw-worms 
in the cleft of the right front foot (between the toes), produced by some fly in Dallas, 
as he was shipped directly from that point, and had been there for two weeks or 
more prior to date of shipment. I took out some 12 or 15 of these worms and 
‘‘planted” them very carefully. I did not know but the fly in north Texas might 
prove to be the gray one, and I was anxious to satisfy myself on this point. 
Some 10 or 12 of the number ‘“‘planted” transformed and the flies appeared in 
eleven days from date of planting, all green with brown heads, exactly like the 
ones I had found in the cat’s foot, and which must, of course, have been deposited by 
flies in this immediate vicinity. ~*~ ~*~ * 
Dr. Francis (Bull. 12, Tex. Exp. Sta.) states that no cases in man 
_ have fallen under his notice, and says: 
Of all our domesticated animals cattle suffer the most from its ravages. They 
occur in wounds from horns, castrating, spaying, branding, dehorning, barbed-wire 
injuries, and often where ticks have burst on the brisket, flank, or just behind the 
4653—No, 5 9 
