1940] 
Hilara granditarsis, Balloon-maker 
55 
HILARA GRANDITARSIS , A BALLOON-MAKER 
A. L. Melander 
College of the City of New York 
On July 31, 1935, while driving through the open forest 
near Moraine Lake, Alberta, I noticed some flies dancing a 
dozen feet above the ground in groups of four to eight among 
the spruce trees. The distinctive feature of this aerial dance 
was the white burden carried by some of the flies, which 
mysteriously glistened in the sunshine. Although the in- 
sects were flying out of reach of the net, now and then one 
would descend and in a short time some two dozen speci- 
mens were captured, all of them males. The species proves 
to be Hilara granditarsis, described by C. H. Curran in the 
Canadian Entomologist, 1926, page 248, from six specimens 
taken by Eric Hearle near Banff, Alberta, and recorded also 
as “swarming under trees”. This habit of swarming in and 
out high up between the trees is rather unusual for Hilara, 
the numerous species of which are most commonly encoun- 
tered dancing close to water. 
The glistening oval bit of frothy matter carried by the flies 
is conspicuous in contrast with the blackish bodies of the in- 
sects hovering with it, and in bulk is even larger than the 
flies. When caught, the flies dropped the balloon, which is 
extremely delicate. On drying, the web collapsed and shrunk 
almost to nothing, and when put into alcohol quickly disin- 
tegrated. 
In Europe, Hilara sartor has similar habits, which have 
been witnessed and commented upon by many entomologists. 
This species likewise is found in coniferous forests in the 
higher altitudes, the males fashioning a white frothy web 
which they carry in the aerial dance to attract the females. 
There are some half-dozen other European species of 
Hilara which are known to build rudimentary webs around 
the small Diptera which they catch and carry for the nuptial 
dance, and it has been suggested that probably most species 
