142 ENTOMOLOGY FOR MEDICAL OFFICERS 



and the posterior basal cross-vein and anal cell are often 

 incomplete. Squamae absent. Antennae of 3 segments ; the 

 3rd segment broad, with an arista which may be terminal, or 

 more or less dorsal. Proboscis short and fleshy, palpi flat. 

 The flies of this large family are predaceous. They haunt 

 damp and shady places, or aquatic vegetation, or may even 

 run on the surface of the water. Among some flies sent 

 from Hongkong by Dr Atkinson as being predatory on 

 mosquito-larvse there were several specimens of a Doli- 

 chopodid. 



Certain species of Brachycerous flies belonging in the families specified 

 below have a long proboscis which may be mistaken for an apparatus for 

 sucking blood. 



(a) Acrocerid<B. Flies with a very small head formed almost wholly 

 by the eyes ; the thorax and abdomen are large and inflated ; and the 

 squamse are of peculiar magnitude. The larvae about which anything is 

 known are said to be parasitic on the young of spiders. 



{b) Nemestrinida. Flies with a complicated wing-venation ; the 4th 

 and 5th veins curve forward and end in front of the tip of the wing ; the 

 empodia are broad, but the pulvilli are often minute. 



(c) Apioceridce. Flies of which some resemble Asilida and some in 

 wing-venation resemble Nemestrinida. Empodia are absent. 



All these three families are small, numerically. 



{d) Bombyliida. The flies of this large family are as a rule thickly 

 hairy, and many of them have a strong resemblance to bees. The head 

 is often small and broadly sessile on the thorax. The wings often have 

 dark markings, and the squamae are small. The pulvilli and empodium 

 are often vestigial. The antennae commonly consist of 3 segments, but 

 the 3rd is never compound. The Bombyliida are flower-flies ; the 

 larvae of some species are parasitic in and on the larvae and eggs of other 

 insects, and certain species are said to do good service to man by 

 destroying the eggs of locusts. 



