88 The Ohio Naturalist [Vol. XIII, N.o. 5, 



nearly straight. From its posterior end arises the tail-like 

 respiratory appendage (Fig. 145, c) which is usually curved 

 anteriorly above or around the body. It is commonly shortened 

 to a length of S to 10 mm. of which the basal segment often forms 

 about two-thirds, the terminal one usually being second in length. 

 The tracheal tubes from these appendages soon become constricted 

 off a short distance within the main body of the puparium and 

 are not functional during most of the pupal stage. 



At the approach of pupation there appears under the larval 

 skin, about one segment back of the anterior or larval respiratory 

 comua, (Fig. 131, b; 145, a), a pair of rounded darkened areas. 

 These soon become elevated to a length of about 2 mm. ; their 

 diameter being about 0.25 mm., rather uniform to near the tip 

 where they round off (Fig. 145, h). They are provided on the 

 distal three-fourths or four-fifths of their length with several 

 hundred, short, rounded tubercles (Fig. 147). These tubercles are 

 somewhat collected into groups, and, especially along the anterior- 

 median surface, are absent over a longitudinal stripe. When 

 highly magnified each tubercle is seen to be ornamented on the 

 tip with about 8 or 9 radial elevations, which I take it are the 

 spiracles. (Fig. 148). The elevations as a whole are called the 

 pupal respiratory cornua. Internally to the puparium they 

 continue as large trachea, which attach to the dorsal part of the 

 prothoracic segment of the developing nymph (Fig. 146, a). 

 There is thus quite clearly a special provision for pupal respiration. 



These might be considered homologous with the prothoracic 

 spiracles of the adult fly; and since they penetrate the puparium 

 about one segment back of the anterior larval respiratory cornua, 

 it might seem improper to consider the larval segment which 

 bears the latter the prothoracic. Nevertheless, it does not seem to 

 me that the point at which these pupal cornua emerge should be 

 considered of much significance. The larval skin at this time is 

 much distorted out of its nonnal shape by contraction and 

 inflation and it would not seem that segmental homology could 

 longer hold. 



The larval respiratory cornua (Fig. 145, a) become fixed at a 

 length of about 0.75 mm. their diameter being slightly less than 

 that of the pupal comua just described. They are recurved 

 slightly to a sharp point. The sub-circular group of rounded lobes 

 at its tip in the larva (Fig. 132), become obscure in this stage. 

 Internally the trachea from these cornua are constricted off and 

 have no connection with the pu])a, at least in its more advanced 

 stages. 



The buccal cavity, antennae, etc., are retracted within the 

 puparium a short distance back of the anterior end where the 

 dorsal elevation begins. Internally the oesophageal framework is 

 flattened against the ventral wall of the puparium from which the 



