DIPTERA 785 



THE BRISTLES OF THE LEGS 



The extensor row. — A row of bristles on the upper surface of femur. 



The flexor row. — One or more rows of bristles placed along the lower surface of 

 the femur. 



The preapical bristle. — A large bristle found on the extensor side on the distal 

 third of the tibia in some families of the Acalyptratae; it is quite distinct from the 

 tibial spurs. This term is sometimes used for a bristle on the femur. 



The tibial spurs. — One or more bristly spurs placed at the distal end of the 

 tibia. 



THE ABDOMINAL BRISTLES 



The discal bristles, — Usually one or more pairs of bristles inserted near the 

 middle of the dorsal wall of the abdominal segments before the hind margin. 



The lateral bristles. — One or more bristles situated on or near the lateral 

 margins of the abdominal segments, above. 



The marginal bristles. — Bristles inserted on the posterior margin of the ab- 

 dominal segments, above. 



Flies undergo a complete metamorphosis. The larvae are com- 

 monly called maggots. These are usually cylindrical and are footless. 

 In the more generalized families the larvse possess a distinct head ; but 

 in the more specialized Diptera there is an anomalous retarding of the 

 development of the head; with these the rudiments of the head are 

 invaginated within the body of the larva and the head does not be- 

 come exposed until the pupal stage is reached. The development of 

 the head in these insects is described in Chapter IV, The pupae are 

 usually either naked or enclosed in the last or the next to the last 

 larval skin. A few are enclosed in cocoons. When the pupa state is 

 passed within the last larval skin the body of the pupa separates from 

 the larval skin more or less completely; but the larval skin is not 

 broken till the adult fly is ready to emerge. . In this case the larval 

 skin, which serves as a cocoon, is termed a puparium. In some fam- 

 ilies the puparium retains the form of the larva; in others the body 

 of the larva shortens, asstiming a more or less barrel-shaped form 

 before the change to a pupa takes place. 



SYNOPSIS OF THE DIPTERA 



Suborder Orthorrhapha. The Straight-seamed Flies, p. 794. 

 Series I. — Nemocera. The Long-horned Orthorrhapha. p. 795. 

 Subseries A. — The True Nemocera. 



The Crane-flies, p. 795. Superfamily Tipuloidea 



The Primitive Crane-flies, p. 796. Family Tanyderid^ 

 The Phantom Crane-fly Family, p. 796. Family Ptychopterid.t- 

 The So-called False Crane-flies, p. 797. Family Anisopid^ 

 The Typical Crane-flies, p. 798. Family Tipulid^ 

 The Dixa midges, p. 800. Family Dixid^e 

 The Moth-like Flies, p. 801. Family Psychodid^ 

 The Midges, p. 802. Family Chikonomid^ 

 The Mosquitoes, p. 804. Family Culicid^ 

 The Fungus-gnats, p. 810. Family Mycetophilid^ 

 The Gall-gnats, p. 813. Family Cecidomyiid^ 

 Subseries B. — The Anomalous Nemocera. 

 The March-flies, p. 820. Family Bibionid^ 

 The Scatopsids. p. 821. Family Sc.\topsid.e 



