FLIES, MOSQUITOES, AND MIDGES 



219 



The transformations are always complete. The most common 

 larvae are termed "maggots," and are headless and footless, white, or 

 light-colored, tapering to a point at the head, usually with a horny, 

 rasplike feeding organ retruded within the head, though many 

 absorb nutriment from the surrounding food through the skin. In 

 other larvae the head and mouth-parts are well developed, while 

 some, like the mosquito wrigglers, lead a most active life. The 

 pupae are usually 

 naked or inclosed in 

 the last larval skin, 

 though a few make 

 cocoons. Instead of 

 being molted, the 

 last larval skin of 

 most common flies 

 becomes hard and 

 distended, and the 

 pupa separates with- 

 in it, so that the lar- 

 val skin practically 

 forms a cocoon for 

 the pupa and is 

 known as a pupa- 

 rium, which looks 

 much like a large 

 brown or black seed. 



The Diptera is 

 one of the largest 

 orders, with over 

 five thousand species in this country (a great majority of which 

 may be classed as injurious), and includes many serious crop pests 

 and most of the insects which carry disease. The different fami- 

 lies are distinguished by the structure of the antennae and of the 

 wing veins, and are divided into two suborders, the typical Dip- 

 tera (Diptera gennind), including all the common families, and 

 the Pnpipara, including three small families of parasitic species, 

 mostly wingless. 



FIG. 347. A crane-fly (Tipitla hebes Loew) 



a, larva, or meadow-maggot ; ^, pupa ; c, adult male fly. 



(After Weed) 



