79 



The second section of the Homoptera is known as Dimera, or those with two jointed 

 feet. In this section we find very much smaller insects with antennae longer than the 

 head and in the winged individuals four wings ordinarily all of the same membranous 

 texture. There are only two genera Psyllidae and Aphidae. The Psyllidae or Flea-lice 

 are small insects found on leaves and in some species raising galls. Although several 

 kinds are known to occur, almost every tree having its own species, very few have been 

 described. They have rather long antennae terminated by two slender bristles : the beak 

 is short and triarticulate, and the eyes are lateral and prominent as in the Cicadas. On 

 the front of the face are three ocelli placed in a triangle, the posterior ones quite close to 

 the eyes. 



The larvae and pupae have the body very flat, and in some species as Psylla celtidis- 

 mamma, Riley, live in galls. I exhibited at the last annual meeting of the Society in 

 Montreal specimens of the galls and pupae of this species, and Prof. Riley then kindly 

 informed me of its proper name, and told me where the only printed description could be 

 found, namely, in an article written by himself for Johnson's " New Universal Cyclopaedia," 

 under the head of " Galls." For the benefit of our members I reproduce this in full : — 

 <£ The Flea-lice produce galls of various shapes and sizes on the stems and leaves of the 

 Hackberry (Celtis). In life habits they differ from all the other gall insects, and agree 

 with their nearest relatives, the Plant-lice, only in being the architects of their own galls. 

 The egg, glued in spring to tender leaf or twig, soon hatches, and under the irritation 

 caused by the young Psylla the gall soon embeds it. Within this gall the insect dwells 

 till it has acquired the pupa state, which is generally by the time the leaves begin to turn 

 and drop, then by means of certain horny spines or thorns at the end of its body, this 

 pupa works its way out of its prison, and once out soon gives forth the perfect fly. The 

 galls made by these Flea-lice are generally woody. Most of them are yet undescribed. 

 P. celtidis grandis (Riley, M.S.) makes on the leaf-stalks a large grayish yellow swelling, 

 which is an exception in being polythalamous. The few cells it contains are more or 

 less filled with a white flocculent matter secreted by the insect." The perfect insect 

 of P. celtidis-mamma appears in September and passes the winter in the crevices of the 

 rough bark of the hackberry on which it underwent its preparatory stages, and 

 adjacent trees. On November 24th last, I collected several specimens in a torpid state. 

 The males are about one-eighth of an inch in length, and the females about one-third larger. 

 The wings are deflexed at the sides of the body, and the hemelytra, which are rounded at 

 the tips, are traversed by three strong nerves (the costal, median, and sub-median), each 

 divided but once and disposed as shown in Fig. 89, which is another species, but serves 



Fig. 89. 



to show the general arrangement ; the underwings are much more transparent and the 

 nerves are very delicate. The colour is grey like the bark of the trees on which they are 

 found ; the antennae which are terminated by two pairs of bristles are composed of ten 

 joints, the eight basal ones yellow striped with black at their upper ends, and the two 

 terminal ones entirely black. The femora are black for the greater part of their length, 



