18 XEUROPTERA. 



anterior wings sometimes indicated by short corneous scales ; 

 the mpjority have four membranous wings, the anterior 

 larger, dilated towards the rounded apex, extending beyond 

 the abdomen; veins with few branches; the subcosta forms 

 a pterostigma, the radius forked, its branches usually again 

 divided, and united in the middle of the wing by a few trans- 

 verse veins. 



The Psocidce have an incomplete metamorphosis ; the 

 larvae and pupae resemble the perfect insects, but the ocelli 

 are wantino;, and in lieu of wino;s thev have more or less 

 developed sheaths. As in Termites {cf. Linnea, xii. p. 18), 

 a peculiar form of pupa appears likewise to exist, in which 

 the development of the wing-sheaths is strangely arrested 

 compared with that of the other parts of the animal. These 

 creatures are not rare, and live in company with the imago 

 and pupae with long wing-sheaths. Mr. Westwood has 

 figured one of these creatures, Introd. ii. fig. 59, 13; the 

 office of these pupae, like those of Termites, is unknown. 

 Certain perfectly-developed individuals have likewise short 

 and rudimentary wings, and it may be conjectured that they 

 are produced from short winged pupae; but this has not been 

 observed. Westwood has united these creatures in the genus 

 Lachesilla. 



The Psocidce very frequently exhibit sexual differences ; 

 in the males the reticulate eyes are larger, often globose, pro- 

 minent, and placed closer together, the forehead narrower; 

 the antennae are stouter, and the pubescence obviously longer ; 

 the whole body is smaller. Sexual differences in neuration, 

 indicated by Mr. Westwood, /. c. p. 19, seem to me very 

 doubtful, and I think that the creatures which Mr. West- 

 wood obligingly showed me pertain to different species. But 

 this is merely an opinion, which, opposed to the assertion of 



