50 
Psyche 
[Sept -Dec. 
DRAGONFLIES AS PREDATORY ENEMIES OF THE 
STABLE-FLY ( STOMOXYS CALC1TRANS ) 
By Charles T. Brues 
Biological Laboratories, Harvard University 
Two accounts have recently been published 1 of observations 
showing that dragonflies commonly capture stable-flies in con- 
siderable numbers. These relate to Florida Gulf beaches, and 
recall similar observations made by us some years ago at a 
second, far distant locality in northern Canada. 
This was on the shores of Cedar Lake in northern Manitoba 
(Lat. 53° N) where we spent a part of the summer of 1936 with 
the primary purpose of collecting fossil insects contained in Cre- 
taceous amber which occurs in quanity on one of the beaches 
bordering the western end of the lake. 
The ever-present swarms of mosquitoes make the short sum- 
mer season almost unbearable for man and beast alike and we 
had been warned that these would be supplemented from time 
to time by other small biting flies. From the description of this 
pest given us by the Indian who selected our camp site it 
appeared probable that it must be the stable-fly. 
This surmise proved to be correct. A fortnight later when 
we returned to camp on the evening of July 5th from the beach 
where our collecting was done we were assailed by numbers of 
stable-flies which bit with the persistence that they exhibit 
whenever abundant, especially in the absence of other mam- 
malian hosts. They were present in considerable numbers while 
the evening meal was being prepared and eaten, and we re- 
signed ourselves to accepting them as camp mates for some 
time to come. 
On the next evening they appeared in still greater abundance 
and the outlook grew more unpleasant. Shortly afterward, dur- 
ing the long twilight which persists for several hours at that 
1 Dove, W. E. and S. W. Simmons. Control of the Stablefly or “dog fly” 
Breeding in Shore Deposits of Bay Grass. Journ. Econ. Entom., vol. 28, pp. 
582-589 (1942). 
Wright, M. Dragonflies Predaceous on the Stablefly ( Stomoxys calcitrans) . 
Florida Entom., vol. 28, pp. 11-13; 31-32. 
