xvn PSOCIDAE 395 



The association of ocelli with wings is nearly constant in 

 Psocidae. The genus Clothilla allied to Atropos possesses 

 very rudimentary wings but no ocelli. Hagen, however, found x 

 that in a certain locality no less than 12 per cent of the indi- 

 viduals of this species were provided with ocelli, a most extra- 

 ordinary variation. 



In some of these apterous forms there is found on each side 

 of the prothorax a tubercular prominence which, according to 

 Hagen, can be considered only as the rudiment of a wing that 

 never develops. Though no existing Insect is known to possess 

 rudimentary wings on the prothorax, we have previously men- 

 tioned (p. 344) that in the Carboniferous epoch appendages of 

 the nature alluded to were not very rare. 



A genus of living forms Hyperetes in which the three 

 thoracic segments are w T ell developed, but in which there are no 

 alar appendages or rudiments, is considered by Hagen to be more 

 primitive than the Psocidae found in amber to which we shall 

 subsequently allude. 



The number of described species of Psocidae does not reach 

 two hundred ; we have, however, thirty species or more in 

 Britain. 2 Nietner observed about the same number in the 

 immediate vicinity of his house in Ceylon. The isolated and 

 remote Hawaiian group of islands is remarkably rich in Psocidae. 

 Two thousand is a moderate estimate of the number of existing 

 species. The largest forms yet discovered belong to the Brazilian 

 genus Thyrsophorus ; they attain, however, a breadth of only 

 about one inch with the wings fully expanded. The Cuban 

 genus Embidopsocus is said to be of great interest from its 

 approximation to Embiidae. It is at present very inadequately 

 known. 



One (or more) very minute Insects of this family Clothilla 

 pulsatoria according to Hagen, Atropos 3 divinatoria according to 

 some other authors is widely known under the name of the 

 death-watch, owing to its being believed to make a peculiar 



1 Stettin, ent. Zeit. xliv. 1883, pp. 299, 305. 



2 For the British species, see M'Lachlaii, Ent. Month. Mag. iii. 1867, p. 177. 



3 The genera Atropos and Clothilla were named after the two fates Atropos and 

 Clotho. AVestwood attempted some years ago to complete the trio by establishing a 

 genus Lachesilla. This proved a failure, the genus being a misconception. As the 

 name Lachesis is in use in various branches of zoology, the desired circle of Psocid 

 fates is likely to remain always incomplete. 



