300 The Ohio Xaturalist. [Vol. Ill, No. U 



should be harckiicd in live per cent, formalin. It is an excellent 

 type for class work so far as its hard ])arts are concerned, but its 

 muscular system is too hioiily modified to serve as a tvpe for the 

 group. 



It is the only representative of its i^^enus in America, and is 

 quite widely distributed. Its larva is characterized by havings its 

 third pair of legs rudimentary and is supposed to have a very long 

 larval stage. 



THE EXTERNAL SKELETAL SVeTEM. 



The body, as in all insects, is divided into a head, thorax, and 

 abdomen. The head contains seven segments and bears a curved 

 spine on its median dorsal surface, and is articulated posteriorly 

 W'ith the prothorax. This segment bears the first pair of legs and 

 presents a smooth expanded surface dorsally. It is articulated 

 posteriorly with the meso-meta-thorax by a narrow area. This 

 constricted area is part of the meso-thorax, which bears ventrally 

 the second pair of legs. On its dorsal surface are borne the elytra 

 or wing covers. Fused with the meso-thorax is the meta-tliorax, 

 which bears dorsally the true v>"ings covered by the elytra an 1 ven- 

 trally the third pair of legs. The last region (^f the body is the 

 aladomen, composed of eight segments, six of which are visible 

 ventrally, but bear no appendages. 



FIXED PART,S OF THE HEAD. 



These are first the epicranium. This term is applied in a 

 general way to the dorsal and lateral regions of the head. The 

 portion of the epicranium lying posterior to the spine is the vertex 

 (i) and the region lying anterior to and including the spine and 

 extending down to a transverse depression near the anterior end 

 of the head is the frons (2). On either side of the spine on the 

 lateral margins of the head lie the frontal ridges ( 3 ) which mark 

 the lateral boundaries of the frons. Below the frontal ridees on 

 the sides of the head lie the eyes (4). The epicranium extends 

 posterior to the eye and ventral to it as the gena (5). Running- 

 back and in from the posterior ventral border of the eye is a slight 

 elevation forming the outer wall of a groove into which the an- 

 tenna fits when retracted under the head. This is called the an- 

 tennal groove (6). The inner border of this antennal groove is 

 the genal ridge (7). It is a well marked elevation with its pointed 

 anterior extremities free and it forms the outer wall of the deep 

 genal emargination (4') into which the maxilla can be retracted. 

 This sclerite (a small chitinized area) surrounding the foramen 

 at the posterior surface of the head is called the occiput, but is 

 not separated by a definite suture frotu the remainder of the epi- 

 craniuiu. The clypeus (8) or epistoma lies on the clorsal sm'face 



