sio INJURIOUS AND USEFUL INSECTS 



The Athericera include three great families, Syrphidae, 

 Muscidee, and CEstridse, besides several small ones. 



The Syrphidse are distinguished by the absence of cavities 

 on the face for the antennas, and by the "spurious vein," a 

 mark which runs along the wing between the third and fourth 

 longitudinal veins. The proboscis is often long, and well 

 suited for exploring the recesses of flowers. Many resemble 

 bees or wasps in their coloration. The flies are remarkable for 

 their activity in pollinating flowers. In sunny weather during 

 summer they can nearly always be seen hovering over flowers. 

 The larvffi differ greatly in their mode of life. Some devour 

 aphids {Syrphus), others inhabit the foulest pools {Eristalis, 

 the rat-tailed maggot), others dwell as scavengers in the nests 

 of bees and wasps ( Volucella) ; some are vegetable-feeders. 



The Muscidae include about a third of the known Diptera, 

 and constitute, therefore, a family of enormous extent. Many 

 of them are so similar to the blow-fly in all that relates to the 

 structure of the head as to be pretty easily recognised as 

 Muscids by all who know that one insect in detail. But the 

 various features alter one by one, sometimes almost insensibly, 

 and it is apparently impossible to draw a clear line anywhere 

 between a typical Muscid like the blow-fly and flies which are 

 notably different. The proboscis is always well developed, 

 but shorter than in many SyrphidK. If the antennae are sunk 

 into a cavity on the face, and if the halteres are covered by a 

 winglet, the fly is certainly a Muscid of the most typical kiiid 

 (sub-family Muscinas), but these characters do not obtain 

 throughout the family. 



To the Muscidae belong the Tachina-flies, with habits similar 

 to those of ichneumons. They do not, like ichneumons, pierce 

 the skin of the caterpillar, but lay' their eggs on it ; the issuing 

 larvae bore their way into the victim. The flesh-flies resemble 

 in structure and mode of life some typical Muscids, such as the 

 blow-fly. Many of the Anthomyids are destructive to crops, such 

 as the cabbage-fly, root-fly, radish-fly, mangold-fly, and onion-fly. 

 The much dreaded tzetze-fly of South Africa is allied to the 

 stable-fly of England {Stomoxys) ; both are nearly related to 

 the blow-fly and common house-flies. 



Muscidae are often distinguished from one another by 

 minute characters, which escape an ordinary observer. The 

 inexperienced entomologist thinks he knows a house-fly when 



