300 NEW YORK STATE MUSEUM 
The sternal setae are the patches of setae on the ventral side 
of each segment between the patches of pedal setae of either 
side [fig.1st]. 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.last] and 
the posterior group as the posterior sternal setae | fig.1ps7]. 
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 of 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 
[p].27, fig.19p]. 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.19as]. This sclerite varies slightly 
in position and extent in different specimens. In some cases 
its mesal end is interpolated 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 17al, is represented a median longitudinal 
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