82 AN INTRODUCTION TO ENTOMOLOGY. 



wood, especially pine, from near the trees ; as such wood is liable to 

 become infested, and the white ants to spread from it to the orange- 

 trees. 



The zoological position of the Termitidae is, like that of the Ephemeridae, 

 near the foot of the insect series. In fact, the form of the wings with Termes 

 is regarded as even more primitive than that of Ephemera; as is also the 

 structure of the thorax, with its equally developed and unusually distinct seg- 

 ments. But the wonderful development of instinctive powers and of separate 

 castes among the white-ants indicates that, although as shown by their struc- 

 ture, they represent one of the lowest groups of winged insects preserved to 

 this time, they constitute the highest development of their line. It is a sug- 

 gestive fact that Hagen, who is the best informed regarding the Termitidae, 

 considers them closely related to the Blattidae, to which the oldest known in- 

 sects belong. 



Family V. — PSOCID^E* 



{Book-lice ct al.) 

 The best known representatives of this family are the minute in- 

 sects common in old papers, books, and neglected collections ; and 



which have received the name of Book-lice. 

 These low, wingless creatures form, how- 

 ever, but a small part of the family. The 

 more typical and winged forms (Fig. 77) 

 bear a strong resemblance to plant-lice or 

 Aphides. The body is oval, the head free, 

 and the prothorax is small. The wings 

 when present are of unequal size, the hind 



Fig. 77. — Psocus venosus. , ., ,. n . , 



pair being smaller. When not in use the 

 wings are folded roof-like over the body, like those of the Aphides. 

 The tarsi are two- or three-jointed. 



There are two sub-families, which are distinguished as follows : 



A. Ocelli wanting; wings absent or incomplete. Atropine. 



AA. Ocelli present ; wings well developed. Psocin^:. 



ATROPINE. — Two genera of this sub-family are represented in 

 this country. In Atropos the wings are absent, the meso- and 

 metathorax are grown together, and the antennae are seventeen- 

 jointed. The common Book-louse is Atropos divinatoria. This species 

 is about 1 mm. in length ; it is grayish white, with black eyes. Closely 

 allied to this genus is ClotJiilla, in which the anterior wings are rep- 

 resented by small convex scales ; the meso and metathorax are free, 

 and the antennas are many-jointed. 



*Psocidae, Psocus : psocho (tpooxa)), to grind. 



