72 BUTTERFLIES 



are compound and their facets extraordinarily 

 numerous, as many as 12,000 being present in the 

 eye of the death's-head moth, and 17,000 in the 

 swallow-tailed butterfly. The range of vision in 

 butterflies is unknown. Of the sense of hearing 

 in butterflies we know very little, but in moths and 

 other insects the antennae are often fringed ; and 

 some most interesting experiments have been made 

 with the antennae of the male mosquito, special hairs 

 of which were found to vibrate to particular notes, 

 those hairs being most affected which were at right 

 angles to the direction from which the sound came. 

 The sound is thus most intense if directly in front 

 of the head ; if one antenna is affected more than 

 the other the head is turned till both are equally 

 affected, and so the mosquito is enabled to direct its 

 flight directly towards the point from which the 

 sound originates ; this power being specially used 

 to aid it in finding the female. 



The Life-History of Butterflies. A butterfly is 

 not always a butterfly, but goes through several 

 phases viz., the egg, the larva or caterpillar, the 

 pupa or chrysalis, and the adult form or imago. The 

 caterpillar phase is the nutritive one ; the adult 

 phase is reproductive and usually short-lived, often 

 not more than a few days, and sometimes limited 

 to a few hours. The eggs are usually protec- 

 tively coloured, and often show very beautiful 

 markings under the microscope. It has been shown 

 that while at least nine-tenths of the eggs and 

 larvae of North American butterflies are destroyed 

 by parasites or disease, such parasites never attack 



