300 NEW YORK STATE MUSEUM 



The sternal setae are the patches of setae on the ventral side 

 of each segment between the i)atches of pedal setae of either 

 side [lag.lst]. The sternal setae of the thoracic segments are 

 frequently' divided transversely into two groups: the anterior 

 group may be known as the anterior sternal setae [fig.la.sf] and 

 the posterior group as the posterior sternal setae [Qg.lpst]. 



In the figures representing the setae of the thorax and ab- 

 domen, the plan originally devised by Dr Friedrich Brauer for 

 showing the setae occurring on the larvae t)f the Oestridae or 

 bot-flies has been followed. By this method each segment is 

 represented as a parallelogram and the topographic arrange- 

 ment of the setae indicated by dots. 



There are nine pairs of spiracles present; one pair is situated 

 on the cephalic margin of the mesothorax and eight pairs on 

 the first eight abdominal segments. The spiracles on the first 

 seven abdominal segments are small and, so far as is deter- 

 minable from their histological structure, are functional. The 

 first abdominal spiracle is on the lateral aspect of the body, but 

 the succeeding pairs gradually converge toward each other till 

 the eighth abdominal segment is reached, which contains a pair 

 of large active spiracles, opening on the dorsal surface, one on 

 either side of the meson. 



Associated with the spiracles of the eighth abdominal seg- 

 ment, there are a number of well marked sclerites. The largest 

 and most prominent is a thick and well chitinized peritreme 

 which completely surrounds the spiracular opening except in 

 front at middle, where there is a very evident interruption 

 [pl.27, fig.l9/)]. Cephalad and laterad of the peritreme there is 

 a prominent sclerite, the anterior sclerite, which is of about the 

 same size as the peritreme and distinctly separated from it by 

 a well marked furrow [fig.ll)«,9]. This sclerite varies slightly 

 in position and extent in different specimens. In some cases 

 its mesal end is inter])olated between the peritreme and the 

 caudal end of the apodeme and in such cases usually contains 

 a prominent, lateral, tongue-like projection. Projecting ceph- 

 alad from each cephalo-mesal angle of the sclerite just de- 

 scribed, there is a long thread-like sclerite, which is one of the 

 chitinized sides of a large dorsal apodeme which is invaginated 

 just in front of and between the anterior sclerites. This apo- 

 deme, together with the anterior sclerites, serves for the attach- 

 ment of a complicated system of muscles which are used in 

 moving the caudal spines. Plate 27, figure 14, represents a 

 longitudinal section of this apodeme, showing the attachment 

 of 11 distinct groups of muscles. The opening of this apodeme 

 was mistaken by Mr Sanderson for the opening of the rectum. 

 On plate 28, figure 17a^, is represented a median longitudinal 



