The Senses of Insects* 



to the brain b\' such a multituck' of facets, there has been considerable controversy 

 among the experts, but the view most favoured is the " mosaic theory " of J. MiiUer, 

 who held that — " An image formed bv several thousand separate points of which 

 each corresponds to a distinct field of vision in the external world, will resemble 

 a piece of mosaic work ; and a better idea cannot be conceived of the image of 

 external objects wliich will be depicted on the retina of beings endowed with such 

 organs of vision, than bv comparing it with perfect work of that kind." 



The longest sight is thought to be possessed by butterflies and moths, which 

 can perceive the movements of rather large bodies at a distance of five feet ; bees, 

 wasps, and their kindred at a distance of two feet ; flies at two and a half feet. 

 Man)/ experiments have clearly proved that Insects ^ 



can distinguish colours at relatively long distances. 

 In other respects they appear to be guided more by 

 smell than sight. 



The sense of smell is — at least in most Insects — 

 seated in the antennas, popularly known as feelers 

 or horns, the pair of slender, many-jointed organs 

 springing from between or in front of the eyes. 

 From the brain a thick nerve passes into each 

 antenna, and fibres from it connect with sensitive, 

 staff-like cells near the extremitv of the antenna, 

 and with accessorv apparatus in the form of pits, 

 or of peg-like or tooth-like projections filled with 

 fluid. In some Insects (such as the grasshoppers) 

 there are three or four hundred of such pits on each 

 antenna. In the rnantis there are no pits, their 

 place and function being taken bv small, hollow, 

 curved teeth with a fine opening at the tij). As 

 might be expected, great variation is found in these 

 pits and processes in the difl^erent families and species 

 of Insects, due no doubt to their different habits. 



The organs of taste are in most cases situated 

 on what mav be called popularlv the palate or roof i'"' '"ormons dcwiopnunt ot thr \vhori,<i 



^ '^ • _ ' _ branches of the aiit<'im;i' is apparently dne to 



of the mouth. Where the construction of the mouth the tact that they are organs of hearing. These 



hairs respond in their movements to a tunnie;- 



doeS not permit of this the\' will be found on fwU giving si^ vibrations per second: and 



' . . - . the hnin of thi' female is of the necessary pitch to 



the organs immediately surrounding the mouth. >■ t tii.-m vibrating. 

 They are somewhat similar to the organs of snu'll, taking the form of pit- or cups. 

 The exact nature of these organs has not been made out without a great amount 

 of experimenting b\- numerous investigators, the dc^tails of which it is not necessary 

 to enter upon here. One or two example^ niii^t sulVicc. Will, a (icrman 

 entomologist, fed certain wasps with sugar, to which they repeatedly returned. 

 Later he took awav the sugar and put alum in its place. The wasps coming eagerly 

 back for more sugar had scarceh' touched the alum when they drew back with 

 most comical gestures of disgust, and cleaned their tongues by running them in 

 and out of their mouth, and frequent!}- stroking them with their fore-feet. He 



Flmlo by] [H. S. Cheavin, F.RM.S. 



He.\d Organs ok M.vle Gn.\t. 



