34 
THE GUIDE TO NATURE 
Useful Flies. 
Downingtown, Pennsylvania. 
To the Editor: 
Last winter, whenever the sun shone 
warm, our attic windows fairly 
swarmed with large flies, long bodied, 
black, sluggish, humpbacked fellows 
with yellowish legs and wings. I man- 
aged to kill most of them from time to 
time, so that very few lived to con- 
tinue the tribe at our place. Since then 
I have learned from a book, “Insects 
and Man,” that they are good flies to 
have around one’s house, for their food 
consists of the larvae of the clothes 
moth and of fleas. I presume that their 
presence in such numbers was owing 
to there being so much clothing, so 
many carpets, etc., stowed away in 
the attic, but so far as we know there 
are no moths or fleas in the attic. I 
think the big flies kept us free from 
those destructive insects. It used to be 
thought, as I have read, that the larvae 
of these flies fed on old carpets and 
clothing, and hence it was called the 
carpet fly. 
Do not we often destroy life through 
ignorance? It seems so. Better the 
idea of the Hindu, who holds all Jife 
to be sacred. 
A. Ashmux Kelly. 
Of this fly (Scenopinus fenestralis) Dr. 
Howard in “The Insect Book” states 
as follows : 
“Its specific name, fenestralis, is due 
to its window-loving habit. The larvae 
of these flies are long and very slender, 
white in color and with apparently 
many joints to the body. They are fre- 
quently found under carpets and in de- 
caying wood ; also in woolen blankets, 
and Riley has stated that he found one 
in human expectoration. This, how- 
ever. was probably accidental. The 
manager of a storage warehouse no- 
ticed many of these slender, white 
larvae under carpets sent in by his cus- 
tomers for storage. He was worried at 
their number, since he supposed that 
their presence might indicate the ad- 
vent of some new kind of carpet moth. 
He was assured, however, that they 
were considered as predatory in habit, 
and that they feed upon clothes moths 
and other insects found in such places, 
such as book-lice. Nowhere, however, 
does there appear to be any record of 
any definite observations on this point. 
One observer tells me that he tried to 
decide this question, but that the in- 
sect intended for prey turned out to 
be more aggressive and ate up the 
Scenopinus larva. They are apparently 
always especially abundant, as I am 
informed by Mr. Chittenden, in the 
sweepings in feed stores, and the flies 
are always to be found around the win- 
dows in such establishments. The 
probability is very strong that they 
feed upon such small, soft-bodied in- 
sects as flour-mites and book-lice. Mr. 
Pergande tells me that he has seen 
them eat the pupae of one of the little 
stored-grain beetles and also disabled 
house-flies which he had ofifered them, 
as well as their comrades of their own 
species.” 
Twin Water Elms. 
Albion, Indiana. 
To the Editor. 
I am sending you a photograph of 
two large water elm trees which are 
completely grown together several feet 
above the ground. I made a thirteen 
mile trip in an automobile to photo- 
graph this tree. 
Rollin Blackman. 
The new Czecho-Slovak Republic 
has already established its own Weath- 
er Bureau at Prague. 
