INTRODUCTION. 



5 



up have the power of motion, which enables the insect to move them 

 in any direction. 



The antennae consist of three parts : the basal joint, commonly 

 distinguished by its form, length, and colour ; the club, formed by a 

 gradual or sudden thickening of the terminal joints, of which the 

 number, form, and size present great variations ; lastly, the stalk, 

 formed by all the joints of the antennae, except the basal, when no 

 club exists, and in case of the existence of a club, of all those 

 between it and the basal one. 



We give as examples the antennae of two beetles, one of the 

 genus Asida, the other of the genus 

 Zygia (Figs. 3 and 4). 



Insects, for the most part, while in 

 repose, place their antennae on their 

 backs, or along the sides of the head, 

 or even on the thorax. Others are 

 provided with cavities in which the 

 antennae repose either wholly or in part. 



During their different movements, 

 insects move their antennae more or 

 less, sometimes slowly and with regu- 

 larity, at other times in all directions. 

 Some insects impart to their antennae 

 a perpetual vibration. During flight 

 they are directed in front, perpendicular 

 to the axis of the body, or else they 

 repose on the back. 



What is the use of the antennae, 

 resembling as they do, feathers, saws, clubs, &c. ? Everything 

 indicates that these organs play a very important part in the life of 

 insects, but their functions are imperfectly understood. Experience 

 has shown that they only play a subordinate part as feelers, and have 

 nothing to do with the senses of taste or smell. There is no other 

 function for them to fulfil, except that of hearing. 



On this hypothesis the antennae will be the principal instruments 

 for the transmission of sound-waves. The membrane at their base 

 represents a trace of the tympanum which exists among the higher 

 animals. This membrane then will have some connection with an 

 auditory nerve. 



The mouth of insects is formed after two general types, which 

 correspond to two kinds of requirements. It is suited in the one 

 case to break solid substances, in the other to imbibe hquids. 



Fig. 3. 



Antenna of a 



species of Asida. 



Fig. 4. 



Antenna of 



Zygia oblonga. 



