158 Transactions. — Zoology. 



Sub-family Liviince, F. Low : Front of head not prolonged 

 into conical processes ; eyes not prominent ; the stalk 

 of the lower branch (cubitus) of the furcation of the 

 primary vein in the forewing much longer than the 

 stalk of the upj)er branch (subcosta). 

 Sub-family Ajjhalarince, F. Low : Front of head either 

 swollen, or prolonged into two conical processes, or 

 roughly ragged ; eyes prominent ; stalk of the cubitus 

 in forewing as long as, or longer than, the stalk of the 

 subcosta in almost all cases. 

 Sub-family Ps////Mzr6', F. Low: Front of head either swollen 

 or produced into two conical processes ; eyes prominent ; 

 stalk of the cubitus in forewing shorter than the stalk 

 of the subcosta. 

 Sub-family Triozino', F. Low: Front of head either swollen 

 or produced into two conical processes ; eyes more or 

 less prominent ; stalk of the cubitus in forewing want- 

 ing (the vein forking directly from the junction with 

 the subcosta). 

 Sub-family Prionocnemidce, Scott : Front produced into 

 conical processes; eyes prominent; stalk of the cubitus 

 in forewing very short ; tibiae slightly serrated. (Are 

 these sufficient distinctions?) 

 It will be seen that the first principal character for differ- 

 •entiation here is a point in the venation of the forewing. As 

 this point -cannot well be made clear by any written descrip- 

 tion, I give diagrams (PI. X., figs. 1, 2) of a wing of Psylla and 

 one of Trioza, in which bd is the stalk of the subcosta, and 

 he (which exists only in the former) the stalk of the cubitus. 

 In fig. 4, belonging to the sub-family Aphalarince, it will 

 be seen that he is a good deal longer than bd ; in fig. 1 it is 

 shorter ; in fig. 2 it is altogether wanting. 



There is a further feature in PsyUidcs which is common 

 to all the sub-families, but of which the variations may be 

 employed for generic and specific differentiation — it is the 

 character of the genital apparatus in either sex. That of the 

 adult female has always the form of more or less sharp- 

 pointed valves produced in a direct line with the abdomen, and 

 within these is the ovipositor. That of the adult male con- 

 sists of a number of appendages erect on the last segment of 

 the abdomen, and having between them the penis ; these 

 appendages are on the dorsal side, and it is not clear what 

 may be their use. The auterior one is usually the largest, 

 sometimes as if with two broad wings or with two lateral 

 slender processes : this is called the " genital plate ;" and on 

 the variations of this and the posterior appendages it is pos- 

 sible to separate species and even genera. The difference 

 between the genitalia of the male and the female is very easily 



