ANTENNA. 239 



describe tliem according to their vai-ious distinctions, and, 

 first, of their situation. 



Antennae are inserted into the head, and connected there- 

 with by means of a ball-and-socket-hke articulation, arising 

 generally in the face between or beneath the eyes ; sometimes 

 also, as already described in treating of the eyes, they arise 

 within a notch on the inside of these organs, which are some- 

 times thereby entirely di^'ided into two parts. They are like- 

 wise, as regards their connexion with each other, contiguous 

 or inserted close together, so as almost to touch each other, 

 or distant when far apart ; sometimes they arise from a pro- 

 duced part of the head, serving either solely as a peduncle 

 for their support, as in the dipterous genus, Ceriaj or as an 

 elongated rostrum, as in the weevils (fig. 56), at the extremity 

 of which the mouth is placed, the antennae being inserted at 

 its sides ; or as a footstalk for the eyes, as in Diopsis (fig. 60), 

 in which the antenna) are placed close to the eyes ; whereas 

 in Achias they are frontal, and the eyes pedunculated. 



As to their composition, they are formed of a variable 

 number of small and generally cylindrical pieces, externally 

 covered with a horny or leathery integument, according to 

 the general consistence of the body of the insect ; and inter- 

 nally softer or vesiculose, having an internal cavity extending 

 throughout the whole length of the organ, inclosing nerves 

 for sensation and muscles for motion ; thus forming a series 

 of tubes connected by a membrane, and attached end to end, 

 varying often as to their respective forms, and having generally 

 but a common motion. xVs to their form, antennae may be re- 

 garded as equal or unequal, according to the equality or in- 

 equality in the length of the respective joints : they may also 

 be regular or irregular, according as they exhibit a uniform 

 appearance, or have the various joints irregularly con- 

 structed. Definitions of a few of the more important modifi- 



