PSOCIDAE 393 



with an elongate efferent duct ; the number of the secondary 

 sacs varies from one to four according to the individual. The 

 testis (Fig. 244, A, l) is a simple capsule ; connected with the 

 base of the ejaculatory duct there is a pair of elongate accessory 

 glands or vesiculae seminales. 



The life-history has never been satisfactorily sketched. The 

 young greatly resemble the old, but have no ocelli or wings, and 

 sometimes the tarsi are of two joints, while in the adult they 

 have three. The antennae have also in these cases a less number 

 of joints in the young stage. The food is animal or vegetable 

 refuse substances ; many live on fungoid matter of various kinds, 

 mouldy chaff being, it is said, a favourite pabulum ; the mould 

 on palings is a source of food to many ; others live on the rust- 

 fungi of leaves, and many frequent the bark of trees. They are 

 able to spin webs, probably by the aid of the lingual glands ; 

 the eggs are deposited, in some cases, on leaves and covered with 

 a web. Hagen says that a peculiar organ, possibly a gland — he 

 calls it a hose ^ — exists at the base of the tarsal claws. In our 

 climate most of the species pass the winter in the egg-state. 

 There may be two generations in a year, perhaps more. 



The nomenclature of the wing-veins of Psocidae has given 

 rise to much discussion.^ The , 



system shown in the accom- ^ ^_-------:??^*^'°°°^\Il/\/~>\ 



panying figure is probably the ^.:;-^ ^^~^^^^^---) 



most convenient ; the subcos- 4'^~ .^^ \^^ ^^T^V^' 



tal vein (2) is always obscure, ^^ ^^s^_\/ ^~^ 2 ^ 



and sometimes can only be " " i'^ 



detected by very minute ex- Fig. 245. — Anterior wing of FMpsoms hrevi- 



,. a " • 4- 4.;„„ stylus. (After Renter.) 1, Costal vein; 



ammation. Some mterestmg 2, subcostal ; 3, radial ; 4, cnbitus ; 4a, 



information as to the minute branches of cubitus ; 5, sector of the radius ; 



, 1 e f. 5a, forks thereof. 



structure and mode or lorma- 



tion of the wings and their nervures has been given by Hagen.^ 



In the young the wings first appear as buds, or outgrowths 

 of the sides of the meso- and meta-thorax ; afterwards the pro- 

 thorax decreases, while the other two thoracic segments and 

 the wing -rudiments attached to them increase. The wings 

 from their very origin appear to be different from those of the 

 Orthoptera, and the changes that take place in the thoracic 



•Psyche, iii. 1881, p. 196. ^ Kolbe, Stettin, ent. Zeit. xli. 1880, p. 179. 



3 Op. cit. p. 209, etc. 



