INSECTS AND MANKIND 443 



reared from these were utilised to start silk- cultivation in 

 the Mediterranean countries, the industry passing west- 

 ward to Italy in the twelfth and to France in the sixteenth 

 century. The prolonged domestication of Bomhyx mori, 

 which is unknown in the wild state, has been accompanied 

 by remarkable degeneration both in the moths and cater- 

 pillars. The former are incapable of flight, and the larvae, 

 as J. H. Watson (191 1) has pointed out, lose after their first 

 moult the dark colour and strong hairy clothing character- 

 istic of their family and become pale, feeble, and almost 

 naked ; while the legs are abnormally reduced, '* their 

 grasping power so small that it is insufficient to sustain the 

 larva when held upside dowTi on a leaf and gently shaken." 

 Fed in its domesticated condition on leaves laid flat on 

 trays, the silkworm is incapable of climbing on twigs, so 

 that " were it put in the open on the mulberry trees it would 

 starve in the midst of plenty, not having strength to climb 

 about for its food as wild species must do." Naturalists 

 who accept the action of the Lamarckian factor in evolution 

 would naturally explain these degenerative changes as 

 definitely induced by the conditions of domestication. 

 Certainly they must be regarded as accompaniments of the 

 silkworm's age-long association with human industry. The 

 large spiny caterpillars of several species of Saturniid moths 

 have been successfully reared for silk-production for many 

 years past ; of these the best known is Antherea tnylittay 

 an Indian moth whose cocoon is the source of " tussore " 

 silk, and A. pernyi, a Chinese species cultivated for the 

 " Shangtung " silk. Watson suggests that the Saturniidae 

 might prove " a sheet anchor in the case of the failure of 

 the production of silk by Bombyx moriJ" The modern 

 textile experts have, however, produced another possible 

 " sheet-anchor " in the now familiar *' artificial silk," the 

 fibres of which are drawn out from wood-pulp. 



Another group of insects which have for long been 

 utilised by man are those Coccidae which produce lac, the 

 resinous substance whence various varnishes, including 

 shellac and lacquer, are made ; the names of these indicate 



