FIELD BOOK OF INSECTS. 



are present and wings are well developed. Of the Atro 

 pidae, two species are rather common in old books and on 

 dusty shelves: Troctes divinatorius (Plate XXI) and Atropos 

 pulsatoria. These creatures are supposed to make a 

 ticking sound, hence the name Death-watch, but this is 

 doubtful. They are also called Book-lice. The Psocidas 

 may be found in groups on bark, each cluster often being 

 covered with a fine silken net spun from their mouths. 

 Their common name is Bark-lice. 



MALLOPHAGA 



Little need be said here about the Bird-lice, except to 

 refer to Plate XXI which shows a common Chicken-louse 

 (Menopon pallidum], a Pigeon-louse (Lipeurus bacillus), 

 and the egg of a louse on the peafowl. Completeness 

 demands a few words about unpleasant creatures, but 

 even these are interesting. Is it not curious that a given 

 species of insect should be confined to the feathers of a 

 single species of bird or the hairs of a certain sort of 

 mammal? This is the case with many Mallophaga. In 

 other cases, the same species of Mallophaga is found on a 

 given kind of bird in the Old World and on a related bird 

 in the New World, indicating that evolution has been less 

 rapid in the parasite than in the host. The winglessness 

 of these insects is undoubtedly a secondary matter a 

 "degeneration" due to parasitism. Unlike the true lice, 

 they do not suck blood but have biting mouth-parts and 

 feed on hair, feathers, and epidermal scales. Metamor- 

 phosis is incomplete. Really these creatures are not bad 

 looking if one views them dispassionately and the egg of at 

 least one of them (see the picture which was redrawn from 

 Bastin's Insects] is most striking. 



SlPHUNCULATA 



The True Lice have been shifted about somewhat in the 

 scheme of classification. Some put them as an appendix 

 to the Hemiptera. They are small, wingless parasites of 

 mammals, including man. Their eyes are either absent or 

 much reduced; their beak is fleshy and unjointed; their 



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