HOW TO KNOW THE IMMATURE INSECTS 



lb. Pupa enclosed with the larval skin; head always retracted, the 

 sclerotized portion occupying a position on the inner side of the 

 ventral surface of the puparium; anterior respiratory organs dis- 

 tinct, either protruded from the antero-lateral angles of the cephalic 

 extremity or from dorsum of base of abdomen; adult usually 

 emerges by forcing off the rounded anterior extremity of the pupar- 

 ium in cap-like form, or the dorsal half of the thoracic portion — 

 the lines of cleavage being along the lateral margins to a point at 

 base of abdomen; rarely emergence is through a rectangular 

 splitting of the dorsum of the puparium. 

 Fig. 558 Suborder CYCLORRHAPHA* 



Fig. 558. a, Toxomerus polltus Say; b, Phytophogo destructor (Say) 

 (U.S.D.A.); c, Sheep bot fly. Oestrus ovis L. (Ohio Exp. Sta.); 

 d, Rhagoletis pomonella (Walsh); e, Leucopis griseolo Fall 

 (U.S.D.A ) 



2a. Antennae much elongated, distinctly visible beneath the pupal 

 skin, normally curving well over upper margin of eyes and extend- 

 ing to or beyond base of wing, in some cases almost to apex of 

 wing; head without strong thocns (except in some Cecidomyiidae 

 and a few Tipulidae); thoracic respiratory organs much elongated 

 or sessile; abdomen sometimes unarmed in the species with short 

 antennae Series NEMATOCERA 3 



2b. Antennae shorter, projecting downward and outward, not curving 

 over the eyes or reaching nearly to base of wing; head usually 

 with strong thorns or horns; thoracic respiratory organs sessile, 

 rarely stalk-like; abdomen usually armed with strong spines or 

 bristles, or if unarmed there are only 4 or 5 distinct pairs of ab- 

 dominal spiracles Series BRACHYCERA 21 



3a. Head with several strong thorns in a vertical series on the median 

 line; pupae living in galls, sometimes in the hardened larval skin 

 and resembling a flaxseed. Fig. 559 Family CECIDOMYIDAE 



Pupation takes place in dif- 

 ferent ways: some pupae are 

 naked, some are borne in pu- 

 paria and a few in silken co- 

 Fig. 559. Monardio sp. COOnS. 



*Key to families is not available. 



200 



