J. C. HUTSON 209 



sometimes a right angle. The anterior dorsal margin of the neck 

 is shghtly reflexed, and is hidden within the occipital foramen into 

 which the neck fits. 



The ventral surface of the neck is shorter than the dorsal and 

 is composed of two plates closely approximate along a median 

 suture and together forming the episternum of Snodgrass. The 

 anterior portions of these plates are narrow and concave, and fit 

 closely under the convex extension of the prothorax to form with 

 it a short cylinder which fits into the occipital foramen, and gives 

 the head freer movement. These plates widen posteriorly into 

 two lobes, whose posterior margins are convex and unite with the 

 concave ventral surface of the collar to form articulations for 

 the coxae. The small triangular sternum lies between the bases 

 of the coxae and adds support to their articulations. 



The dorsal surface of the collar is somewhat flat anteriorly, but 

 slopes upwards, sometimes ^^Imost vertically, to a rounded cre.st 

 at the back, which is divided by a median furrow into two lobes. 

 The anterior dorsal surface may be slightly arched and almost 

 horizontal so that it forms nearh^ a right angle with the posterior 

 surface, the lobes being rounded and not prominent, or it 

 may form an acute angle with the posterior surface, in which 

 case the lobes are rather sharp, with their crests higher than the 

 mesonotum. 



The posterior region of the collar is somewhat vei'tical and 

 extends over the anterior margin of the mesonotum which has a 

 broad median projection under it. 



Between the lateral edge of the episternum and the anterior 

 lateral margin of the collar is a very narrow plate, called the 

 epimeron, which has been partly telescoped under the collar. 

 This narrow strip appears to be the continuation of the anterior 

 margin of the neck. The epimeron suddenly grows wider ven- 

 trally and extends to the base of the coxa on each side. The 

 collar extends ventrally as far as the epimeron and its lower 

 posterior margin projects over a portion of the mesothorax in 

 the form of a semicircular lobe, called the prothoracic lobe by 

 Fernald. This lobe touches the side of the mesonotum above 

 and covers a depression on the mesopleuron, at the bottom of 

 which lies a spiracle. 



TRAN.S. AM. ENT. SOC, XLV. 



