THE CLASSIFICATION OF INSECTS 



171 



of the chewing and crushing biting common to beetles, grass- 

 hoppers and other insects with jaw-like mandibles, some, as 

 the mosquito, have elongate mandibles, slender and sharp- 

 pointed, so that they act as lacerating needles to make punc- 

 tures in the flesh of animals or tissues of plants. Most flies, 

 however, have no piercing beak, but, like the house-fly, lap up 

 liquid food with a curious folding fleshy proboscis which is the 

 highly modified labium or under lip. They feed on flower 

 nectar or any exposed sweetish liquid, or on the juices of 

 decaying animal or plant substances. 



FIG. 81 Horse-fly, Tabanus punctifcr. (About i| natural size.) 



All the Diptera have a complete metamorphosis, the young 

 hatching from the eggs as footless and even headless larvae 

 (maggots, grubs), usually soft and white, and in many cases 

 taking food osmotically through the skin. Larvae of different 

 kinds of flies live under a great variety of conditions; some in 

 water, some in the soft tissue of living plants or decaying 

 fungi, some in the flesh of live animals or in carrion, some 

 underground, feeding on plant roots. 



The pupae of the more specialized flies are concealed in the 

 thickened and darkened last larval molt, the whole puparium or 

 chrysalid looking much like an elliptical brown seed. In some 



