ASirJD^E. 53 



three submarginal and five })()sterior cells always present; 

 first and fourth posterior cells and the anal cell open or closed. 



The family Asilidte or Robber-flies is one of the largest and 

 best known among diptera, including nearly three thousand 

 species, distributed among about one hundred and fifty genera. 

 Many of the species are consi)icuous for their large size, the 

 largest measuring nearly two inches in length, while the small- 

 est known species are seldom less than a third of an inch. 

 They are the most predaceous of all flies in their habits. The 

 greater i^art of them rest u})on the ground, and fly up when 

 disturbed, with a quick buzzing S(mnd to alight again a short 

 distance beyond. Some of the Laphrinae have a striking 

 resemblance to large humble bees, and are usually observed 

 resting upon foliage about the borders of forests. All their 

 food, which consists wholly of other insects, is caught upon 

 the wing; their luckless victims when once seized in their 

 strong feet are powerless to escape. Other flies and 

 Hymenoptera are usually their food, but flying beetles, es- 

 ])ecially the Cicindelidai are often caught and they are known 

 to seize and destroy large dragon flies. In an instance that 

 the writer observed, a female seized a pair of her own species, 

 and, thrusting her proboscis into the thorax of the male, car- 

 ried them both off together. 



The larvce live chiefly in rotten wood, under bark, or in soil 

 containing decomposing vegetable nuitter, under leaves, etc., 

 and feed upon grubs and other larvae. The larvte are cylin- 

 drical in shape, with ])archment-like skin, the abdominal seg- 

 ments sometimes girdled with rounded tubercles, or with 

 abdominal protuberances for locomotion. The pupffi are free, 

 Avith strong booklets at the anterior end, and the abdomen is 

 ])rovided with spiny girdles, mixed with hairs above and be- 

 low ; the last segment has two short divaricate booklets and 

 several smaller ])rojections. 



The young larvie sonuitimes bore their way completely 

 within tlie bodies of other larva', remaining there till their 



