130 KANSAS UNIVERSITY SCIENCE BULLETIN. 



edge of the foramen next to the frons, which is easily torn 

 away in dissection. At first the labium is merely a mem- 

 branous band with only very slightly raised edges, which in 

 this region of the organ are somewhat chitinized. These edges 

 gradually become more raised and lose their chitinization until 

 finally a little before the bend in the labium these edges be- 

 come broad flaps which come together, and from this point to 

 the tip there is left only a slit (29-4:), The epipharynx lies 

 naturally against the floor of the labium, but it can be lifted 

 clear, together with the remainder of the parts, for some dis- 

 tance from this position. The first or basal segment of the 

 labium is membranous, not chitinized, since it is so well pro- 

 tected between the procoxse in a membranous fold. Each 

 procoxa is placed very close to and almost fits the foramen 

 laterad and dorsad of the frons (29-1, for). The first seg- 

 ment of the labium lies between the front coxse, embedded in a 

 membrane, and these coxse almost meet over (ventrad of) it 

 (29-2 and 31-1). 



The attachment of the labium to the prothorax, in this case 

 to the region between prothorax and mesothorax, typical of 

 the Homoptera, is very strong as compared with that between 

 labium and head. In fact, in most cases when the head was 

 removed from the rest of the body the labium remained fas- 

 tened to the thorax but tore loose at its base from the head. 

 Meek mentions such a condition as present in the cicada, call- 

 ing the structure on the thorax to which the labium is attached 

 a "collar," describing it in the following words: "A heavy 

 membrane attaches the labium to a chitinized collar of the 

 thorax." In Pachypsylla this collar is a chitinized process 

 (27-4) embedded in the membranes between the prothorax 

 and mesothorax (29-2, p). This process consists of two 

 heavily chitinized structures, flattened and concave at their 

 distal ends and large and swollen at their proximal ends, which 

 are connected by a curved, chitinous rod as a sort of yoke, 

 which is immediately under or dorsad of, and partly encircles, 

 the labium just cephalad of its bend (29-4, b). The bases of 

 this process are embedded in the membrane dorsad and some- 

 what caudad of the cephalic margin of the mesothorax, from 

 whence the process projects ventrad and cephalad. The distal, 

 parallel ends of these are roughened on their edges and hol- 

 lowed out to form a groove, which, assisted by membranous 



