363 



CHAPTER X. 



Part I. 



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PSYLLID^I. 



Considered as a distinct group, this family of insects is very easily 

 overlooked, even by workers who have a fair knowledge of economic 

 entomology, inasmuch as they may be mistaken for the Aphididae or 

 green-fly on the one hand, and the Cicadidae on the other. 



The following may be taken as the chief characteristics of the 

 group : Head produced in front, but somewhat broad ; eyes- large and 

 prominent ; three ocelli present, one close to each eye and the third in 

 the middle of the forehead. Antennae inserted in front of the head, 

 usually ten-jointed, with two large basal joints, the remainder of the 

 joints filiform, and terminated by a slender forked bristle. 



The thorax is well developed. The wings, when at rest, are folded 

 roof-wise over the body. As the wings are nearly all equally clear, 

 they may be termed four in number, and not elytrae and wings. The 

 venation of the upper is very simple. The subcostal vein passes 

 obliquely across the wing, ending in a small indistinct stigma, and 

 dividing the whole wing into seven distinct open cells. 



The front pair of legs are rather shorter than the other two pairs. 

 All legs are well formed for leaping. The tibiae in the second pair of 

 legs are somewhat longer than in the first pair, and still longer in the 

 third pair. In the hinder pair the tibiae have a few blunt spines at 

 the apex. The tarsi are two-jointed, and terminated by a distinct 

 claw. In the hinder pair of legs, the second joint of the tarsi, like 

 the tibiae, have also a few blunt spines. There is a very notice- 

 able peculiarity in the adult insects on the food-plant viz., that 

 they take to flight very reluctantly from approaching danger, and 

 seem to depend almost entirely on their leaping powers as a means 

 of escape. 



