210 THE CANADIAN ENTOMOLOGIST 



curved posteriorly, or following, to a great extent,, the contour of the 

 hind margin of the eye, and which plainly do not reach the hind 

 margin;' and those which, although diverging posteriorly, are 

 straight or convergingly curved, and meet the hind margin or 

 approach it exceedingly closely. 



Carination of head. In these we have the most unsatisfactory 

 taxonomic characters, for in so many spacies they are obscured at 

 the junction of vertex and face, and there is considerable variation 

 in such characters as the furcation of the median frontal carinse. 

 In Homoptera such variation is common in all characters which 

 undergo a great alteration at the last ecdysis*. In all nymphs of 

 DelphacidcC with which the writer is acquainted there are two 

 medio-longitudinal carina? on the face which, in certain species 

 amalgamate to a greater or lesser extent, the extent of amalgam- 

 ation being variable. For this reason it has been necessary to 

 place certain genera in two or three locations. With a wider 

 knowledge of the species of certain genera, and their variations, 

 than the writer possesses it is highly probable that more definite 

 characterisation can be constructed. 



Tibial spines of the hind legs have been used for taxonomic 

 purposes, but they do not appear to be of great value for there is 

 great specific variation; usually there is one at the base, one about 

 middle and several at apex. It is possible that the proportional 

 length of the first joint of hind tarsus and the absence or presence 

 of one or two spines near the middle can be used more than they 

 have been, also the proportional length of the front tibiae. 



For specific work it is absolutely necessary that the male 

 genitalia be examined, and a use of it for generic distinction is 

 possible in certain groups. 



In the orismology the writer has used the term vertex as 

 indicating that portion of the head, excluding the eyes, which can 



*An extreme case of this nature is foimd in the Derbid gems Zoraida in 

 which the face is only a narrow carina (composed of two carinse more or less 

 amalgamated) betwe-m the eyei; in the nymph the face is broad with two 

 median carina well separated. In the adult the wide face still exists but is 

 invaginated med-o-longitudinally, the outer carin^e of the nym )h forming the 

 narrow face of the adult. This can be demonstrated by boiling a head of 

 Z. insulicola (perhaps any other species) ia caustic potash when the face will 

 open. Several genera have been erected upon slightly widened faces (i.e. 

 Shirakia and Zomidoides) some of which are likely to be found to be miperfectly 

 developed Zoraida. 



