178 



whereas in the Brachycera they are either short and inconspicuous or 

 project ahnost in a straight hne across the front of the head, being 

 usually armed with thorns, or they project divergently downward and 

 are frequently armed with strong thorns. The abdomen has usually 

 7 pairs of lateral spiracles, but in most of the aquatic forms these are 

 not distinguishable. 



Division Brachycera 



As mentioned under the previous heading, the pupae of this group 

 very frequently have spines on the antennal sheaths and, in addition, 

 similar spines on protuberances on the face or other portions of the 

 head, and also on the thorax. The prothoracic spiracles are sessile or 

 but slightly elevated except in some Empididae and Dolichopodidae. 

 The abdomen has 7 pairs of lateral spiracles; the segments usually 

 have girdles (1-2) of spines, thorns, or hairs; and the apical segment 

 is usually armed with two or more strong terminal spines or stout 

 processes. Only in the case of the Stratiomyiidae are the pupae en- 

 closed in the last larval skin. 



The pupae of Coleoptera and Hymenoptera may readily be sepa- 

 rated from those of Diptera by the mandibulate mouth-parts and the 

 presence of four wing-pads, while the latter character will also sepa- 

 rate those of Lepidoptera, though usually the under wings, or posterior 

 wings, are visible only in the form of a narrow strip along the caudal 

 margins of the front pair. 



Suborder CYCLOEEHAPHA 

 Divisions Acroptera, Aschiza, and Schizophora 



All the divisions of this suborder may be distinguished by the fact 

 that the pupae are enclosed within the indurated last larval skin. The 

 absence of a well-developed head will readily separate the puparia of 

 this suborder from those of Stratiomyiidae ; in the case of Lonchop- 

 teridae, which resemble the latter family, there is no distinct head, there 

 are only 9 distinct segments, and on the dorsum of the second ab- 

 dominal segment there are horn-like respiratory organs as in Phoridae. 

 The chitinized' structure of the puparia itself will serve to separate 

 them from those of the Cecidomyiidae that pupate under similar con- 

 ditions, the integument of the latter being of a rather flimsy nature. 



In Lonchopteridae, Syrphidae, Phoridae, and many Muscidae and 

 Anthomyiidae a pair of thoracic respiratory organs are developed upon 

 the first or second abdominal segment in the puparia. These organs 

 do not appear until the pupa is formed, and their mushroom-like 

 sprouting comes rather as a surprise to the observer. 



