318 [NJUBIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



DIPTERA (Order) 



TWO WINGED INSECTS 

 TRUE FLIES 



This order is exceeded in the numbers of described species only by 

 the order Coleaptera and possibly by the order Lepidoptera and is one 

 of vast importance to health as well as to agriculture. Large numbers 

 of the members feed upon decaying vegetable and animal matter, many 

 are injurious to growing plants, while still others are predaceous and 

 parasitic upon other insects and animals. When wings are present 

 there are only two. The male coccids or scale insects and some of the 

 may-flies are the only other insects thus characterized. 



All have complete metamorphoses. The larva; are legless and com- 

 monly known as maggots. They are usually headless, though some, 

 as mosquito wrigglers, have well-developed heads. The pupa may or 

 may not be enclosed in a tough larval skin, known as a puparium. 

 The adults are commonly called flies, though this term is also given, 

 usually with some prefix, to many other insects. 



The mouth-parts are for piercing, lapping and sucking. 



The life histories and habits of flies vary considerably. Most species 

 lay eggs, while a few give birth to living maggots and others bring 

 forth young already developed to the pupal stage. The latter flies are 

 always parasitic. The feeding habits of the maggots differ greatly. 

 A great many are terrestrial and feed upon decaying plant or animal 

 matter or upon living plant or animal hosts, while others are aquatic 

 in habits though they may have similar diets. 



The control of this group is very difficult, due to the great produc- 

 tiveness of the females of some species and the secluded work of the 

 larva?. A contact spray is usually recommended for sucking insects, 

 but is of little avail against the maggots, while poison-baits and sweet 

 poisoned sprays are readily lapped up by adult flies and give some 

 aid as control measures. The reduction of the number of maggots is 

 only accomplished by the destruction of the adults. Carbon bisulfid 

 is sometimes used to kill maggots in the soil, as in the case of root 

 maggots. 



To what extent natural enemies check the tremendous increase of 

 Hies is not well known. Predaceous insects prey upon the larva? and 

 adults, while internal parasites attack nearly all stages. 



THE ALFALFA CRANE-FLY 



Tipula simplex Doane (Family Tipulidae) 



(Fig. 313) 



Description. — The adults are long-legged, slender-bodied insects of 

 a light brown color. The females are wingless, while the males are 

 winged and somewhat smaller, lighter in color and with longer and 

 more delicate legs. The average length of the adult female is about 

 ^ inch. 



The eggs are dark gray, oval and very small. The maggots are dirty 

 white or light brown, very rough, with projections or breathing spiracles 

 at the posterior end, and from | to 1 inch long. Due to their tough 

 skins, they are often called "leather jackets." The pupa? greatly 

 resemble the larvae in shape and color at first, but gradually assume 



