INSECT. 



849 



to notice that (hey are exceedingly sensitive, and are ( 

 evidently of the highest degree of service to the 

 insect. From their great diversity of structure they 

 are employed by entomologists as affording the most 

 satisfactory characters to distinguish the various 

 genera, \-c. It is therefore essential that we should 

 enter more into detail respecting their peculiarities. 

 W,; will therefore describe them according to their 

 various distinctions, and, first, of their situation. 



Antennae are inserted into the head, and connected 

 therewith by means of a ball and socket-like articu- 

 lation, arising generally in the face between or beneath 

 the eyes; sometimes also, us already described in 

 treating of the eyes, they arise within a notch on the 

 inside of these organs, which are sometimes thereby 

 entirely divided into two parts. They are likewise, 

 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 produced part of the head, serving either 

 solely as a peduncle for their support as in the dip- 

 terous genus, Ceria ; or as an elongated rostrum as in 

 the weewils (fig. 06), 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 antennae 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 internally softer or vesi- 

 culose, having an internal cavity extending through- 

 out 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 at- 

 tached end to end, varying often as as to their 

 respective forms, and having generally but a common 

 motion. As to their form, antennae may be regarded 

 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, accordingly exhibit- 

 ing a uniform appearance, or having the various 

 joints irregularly constructed. Definitions of a 

 few of the more important modifications of form 

 will be serviceable to the beginner, who would other- 

 wise have to contend against a series of technical 

 names which would be unintelligible to him, unless ac- 

 quainted with the Latin language, from which they 

 are generally derived. 



Variously formed Antennae. 



Filiform, when the antennae are of equal thickness 

 throughout their whole length, like a thread 

 (fig. 69). 



Setaceous, when they insensibly diminish in thick- 

 ness to the tip (fig. 70). 



Monti/form, when they are formed of globular joints 

 resembling a. necklace of pearls (fig. 71). 



NAT. HIST. Vor.. 11. 



Cylindrical, when they are of equal thickness 



throughout, with the joints scarcely discernible. 

 Prismatic, when they resemble a prism, or are 



formed of three sides (fig. 72). 

 Entiform, angulated at the sides, large at the base, 



but gradually terminating in a point, like a sword 



(fig. 73). 



Subulated, short and pointed at the tip. 

 Fusiform, narrowed at the two extremities and 



thickened in the centre, like a spindle. 

 Aristate, when the antennae are terminated by a 



fine bristle (fig. 74). 

 Dentate, when the joints are armed with short 



spines (fig. 77). 

 Seirate, when the joints are triangular, one of the 



angles being internally produced, like a saw 



(fig. 76). 

 Pectinated, when the joints are furnished with a 



long and slender tooth, general!}' arising from 



the base or extremity of each, thus resembling a 



comb (fig. 78). 

 Bipectinated, when each joint produces two long 



teeth, or filaments. 

 Flabellated, when the branches are very long and 



flattened like the rays of a fan (fig. 78 beneath). 

 Ramose, when several of the joints throw out 



branches (fig. 79). 

 Furcate, when the antennas are divided into two 



branches like a fork (fig. 80). 

 Geniculated, when they are bent at an angle, gene- 

 rally at the extremity of the long basal joint, like 



an elbow (fig. 81). 

 Clavate, when they gradually thicken to the tip 



like a club (fig. 82). 

 Capitate, when they are terminated by a knob-like 



mass or head. 



Perfoliate, when the terminal joints of the club are 



not closely applied to each other. 

 Lamelliform, when they are terminated by a club 



greatly produced on one side, the joints of which 



form plates applied against each other (fig. 83). 

 Fissile, when they are terminated by a cleft 



knob. 



Plumose, when they resemble a feather (fig. 84). 

 Auricidate, when one of the basal joints is dilated 



into a shield or ear partially covering the rest 



(fig. 85). 

 Palmated, when the antennae are short, and divided 



by deep incisions. 

 Nodose, when they are thickened in various parts, 



like knots. 

 Verticillate,\v\\en whorls of hair are placed at equal 



distances upon the joints (fig. 86). 

 Fasciculate, when abundle of hairs is placed on one 



side of each joint. 

 Scnpiferous, when a single or very thick bundle of 



hair is placed upon one of the joints. 

 H H H 



