No. 394.] A BALLOON-MAKING FLY. SII 
the balloon when the male is flying. It is frequently carried 
farther back, apparently by the hind legs alone. Fig. 2 shows 
the position assumed in copulation, the male underneath rolling 
the balloon. 
No illustration could properly show the beauty of the balloon, 
still less could anything worthy of the subject be made from 
the shriveled and flattened specimens that now remain in our 
Fic 3. 
possession. The half-tone (Fig. 3) serves only to show the way 
it is formed of bubbles. 
The only published observations at all comparable with these 
are on the European: species of Hilara, a genus of Empidz 
closely related to Empis, and especially on Hilara sartor 
Becker. Several entomologists have published articles on the 
species, and there has been considerable difference of opinion 
as to the nature and purpose of the structure carried by the fly, 
as well as the method of carrying it. Professor Mik, in the 
