SENSES. 9 



The sense of smell is also probably present, and is believed to lie in the 

 antennae. Some insects (e.g., locusts) can almost certainly smell water, 

 a feat we are incapable of because our olfactory organ is always damp. 

 Others can certainly smell flowers, carrion, etc., and their sense of smell 

 is probably far keener than our own. 



Taste is believed to be a sense functional through certain organs in 

 the mouth-parts. 



Touch is another sense probably connected specially with the antennae 

 and the little palps on the mouth-parts. 



Other senses that we do not now use certainly occur; possibly we 

 were once possessed of the " sense of direction/' as many insects are ; 

 other obscure senses we are able dimly to perceive only after a close study 

 of the habits of insects, although we cannot connect any special sense 

 organs with them. Among these we may include the very peculiar sense 

 shown in the phenomenon known as " assembling." It is known that if 

 the females of certain moths are exposed in a cage, the males of those 

 species will come in numbers and from considerable distances. These dis- 

 tances in some cases extend to several miles. By what sense the males 

 become aware of the presence of the female is not known. The pheno- 

 menon is utilised in the rearing of wild silk moths in India, the reared 

 female attracting the wild males from the jungle. 



It is impossible to discuss the senses of insects in further detail in 

 this book. Man cannot hope to comprehend them. The fact that a 

 butterfly knows " by instinct " the plant on which its young will feed 

 seems marvellous when we recollect that the butterfly could not remem- 

 ber what it fed on as a caterpillar, the metamorphosis having come after 

 its caterpillar stage and obliterated its memory of larval life. There are 

 countless instances of this kind, and we can only study the activities of 

 insect life with admiration at the wonderful " instincts" and senses with 

 which they are endowed. 



Among other curious phenomena may be marked the formation and 

 migration of swarms of insects, such as locusts. This phenomenon is also 

 little understood ; it occurs in a small number of insects belonging to 

 different families. The locusts arc the best known instances in India, 

 two lands of which move in swarms over many hundreds of miles. It 

 occurs also in moths, butterflies, dragon-flies, in the larvaa of certain flies 

 and in] caterpillars. Large numbers of these insects gather together, form 

 swarms and migrate from place to place. This phenomenon probably 

 originates in the necessity of moving to fresh places in search of food. 

 Insects which multiply very rapidly into enormous numbers may have 

 found it a necessity to move often, the habit thus becoming a settled one. 



