306 INSECT ARTIZANS AND THEIR WORK 



light than the other sex, the less luminous sex has, 

 as a rule, the best developed eyes ; this is especially 

 marked in the case of the large eyes of males of 

 species in which the female is luminous, but 

 apterous." 



There is very little difference in the appearance 

 of the larvae and the fully developed females. From 

 the laying of the egg to the emergence of the 

 perfect insect from the chrysalis a period of about 

 twenty-one months is covered, the insects becoming 

 inactive during winter. Both larvae and perfect 

 insects feed upon snails and slugs. Such creatures 

 when attacked exude a great amount of slime, and 

 the larva has a special implement for dealing with 

 this when it has got smeared over its body. Such 

 a coating might seriously interfere with the proper 

 action of the breathing apparatus by closing some 

 of the spiracles ; but from the last segment of its 

 body the insect can protrude a bunch of whitish 

 filaments which it uses as a brush by curving the 

 flexible hind body and drawing the brush over the 

 soiled part. 



As to the nature of the luminosity of the Glow- 

 worm and other Lamp-bearers, there is much 

 difference of opinion among the authorities. One 

 says it is due to the slow oxidation of a special 

 substance in the cells of the light-giving region, 

 controlled by the nervous system. Another says 

 he has found in the Fire-fly that it is due to the 

 reaction of two substances called luciferase and 

 luciferine, the former found only in the luminous 



