102 BRITISH INSECTS 



strikingly like wasps and bees. The chief mouth-part 

 is the fleshy labium, but there is also a series of 

 slender, pointed lancets. To what use, if any, the 

 latter are put is not known, seeing that the food of 

 these insects consists chiefly of pollen. " Honey is 

 also doubtless taken by some species (writes Dr. Sharp), 

 but the lancet-like organs appear equally ill-adapted 

 for dealing with it." The form of the larva and the 

 nature of the life-history are very diverse in this 

 family. The hover-flies that frequent our gardens lay 

 their eggs on plants, and their maggots do good 

 service to mankind by preying on aphides, whose 

 juices they suck. The common drone-fly, 1 which 

 resembles an overgrown hive-bee in appearance, is 

 one of a group of species whose larvae are the " rat- 

 tailed maggots " that feed in liquid filth or dirty 

 puddles. The remarkable " tail" contains an ex- 

 tension of the tracheal system ; and as it is capable of 

 extension or withdrawal, the larva is able always to 

 keep the tip above water, thus securing a constant 

 supply of air. In another genus, 2 the maggots live in 

 the nests of bees and wasps, where they were once 

 believed to prey upon the grubs, but are now known 

 to act as scavengers. Other Syrphid larvae feed in 

 fungi or decaying vegetable matter ; while those of the 

 narcissus-fly 3 a particularly humble-bee-like species, 

 very variable in colour burrow into living bulbs, and 

 cause much mischief, both in this country and in 

 Holland. 



The bot-flies, 4 in their larval state, rank among the 

 most revolting of all parasites, feeding as they do in 

 the nasal passages, under the skin, or in the alimentary 



1 Eristalis tenax. 2 Volucella. 



3 Merodon equestris. 4 (Estridce 



