158 



INSECT TRANSFORMATION 



Mallophaga as a sub-order of the latter. Among the Psocidae, 

 the family which represents the Corrodentia in these countries, 

 are found many small insects with relatively ample wings that 

 live on the bark of trees, in moss, and other vegetable growth. 

 It is of interest to find that in several genera of these psocids 

 Mesopsocus for example 1 the wings in many adults remain 

 in the condition of short pads or rudiments, like those of young, 

 growing insects ; within the same species wings may or not be 

 be developed. The best known of the Psocidae is probably 



a 



FIG. 90. CATTLE-BITING LOUSE (Trichodi'des scalaris). 

 a, female ; b, egg. x 24. From Carpenter, F.con, Proc. R. 

 Dublin Soc. II. 



the tiny pallid insect Atropos divinatoria which may be seen 

 running about in decaying dry wood, among old books and 

 papers or in neglected natural history collections ; this creature 

 is often known as a " death-watch " because of the tapping 

 noise audible in the silence of night which it makes with 

 its mandibles on wood or other material in which it lives. 

 Now Atropos has no trace of wings in any stage of its life- 

 history, resembling in this respect the whole of the Mallophaga. 



1 P. Bertkau : " Ueber einen auffallenden Geschlectsdimorphismus bei 

 Psociden". Arch. /. Naturgesch., XLIX., i. 1882. 



