112 Annals Entomological Society of America [Vol.1, 



The Ganglia and Connectives of the Thorax. 



In the thorax (Figs, i and 2) there are three quite similar 

 ganglia, which are the nerve-centers of the pro-, meso- and meta- 

 thoracic segments respectively. These ganglia are situated near 

 the floor, ventrad of the longitudinal-ventral muscles and caudad 

 of the center of each respective segment. They are of relatively 

 large size, circular in outline and decidedly depressed. 



The first thoracic ganglion (/) is connected with the sub-, 

 •oesophageal ganglion by two comparatively long connecti\-es. 

 On entering the prothorax they diverge as illustrated in Fig. 2. 



The connectives of the two following segments are but half the 

 length of those described above. They are also distinct from 

 each other, enclosing betw^een them the furcae (/) to which the 

 ventral diagonal muscles of corresponding segments are attached. 



The nerves of the first thoracic ganglion (Fig. i, 2, /). 

 From either of the lateral borders of this ganglion there arise three 

 nerve-trunks (.4, B, C), the first and third of which are as large 

 in diameter as the connectives. The anterior nerve trunk (A) 

 -extends laterad and breaks up into numerous branches which in 

 Fig. 2 have been labeled: a, i, 2, j; b, i, 2, j, and c, i, 2, j, 4. 

 The origin and direction of these nerves is evident from the 

 illustrations and need not be described in detail. The second 

 branch of a passes along the floor of the segment and innervates 

 the neck. Branch 9 also follows the floor of the segment and 

 extends to the caudal portion of the head. Nerve h supplies 

 the latero-dorsal portions of the segment ; branch 4 of nerve c runs 

 €ephalo-laterad, innervating the lateral portion of the neck. 



Nerve B is relatively smaller than either A or C. It forks 

 near its origin, giving the appearance of two distinct nerves. It 

 innervates the ventral and lateral muscles. 



Nerve C. The nerve of the leg consists of one large main 

 trunk, which near its origin gives rise to a slender branch. 



The nerves of the second and third thoracic ganglia 

 (Fig. 2, //, ///). The general distribution of the nerves of the 

 above two ganglia is very much the same and therefore will be 

 ■described together. 



Nerve A, which in the larva is a rather small nerve, becomes 

 in the adult quite enlarged and constitutes the alar nerve. 



Nerve B resembles that of ganglion / except that it has an 

 additional branch (i), which is analogous in appearance and dis- 

 tribution to "a" of nerve trunk A of the prothoracic ganglion. 



