44 GNATS OR MOSQUITOES — CHAPTER III 



organ ; as he believes that it is by the vibrations of these 

 bristles that nutritive particles are directed into the mouth. 

 Anterior again to the clypeus is a small, rounded, median 

 prominence, the hibrum or dorsal plate of the first 

 metamere. 



The eyes are large and placed laterally, forming a sector 

 of about 150", and close behind them may be distinguished 

 a minute ocellus, generally of oval form. The antennae 

 spring from the antero-external corners of the third meta- 

 mere, and form a pair of short, curved horns, fairly freely 

 movable on their basal articulation with the head, but 

 elsewhere rather rigid. The greater part of the organ 

 consists of a rather stout basal joint, which is provided at 

 the inner side of its distal extremity with a tuft of strong, 

 compound bristles. 



The next joint is less than half the length of the basal, 

 and is distally armed with a few long, stiff bristles, while, 

 like the basal joint, it is beset throughout its length with 

 stiff, short spines. The last portion of the antenna or 

 fiagellum is very minute, although there are indications 

 that it is in reality composed of three very short articula- 

 tions. Besides the fiagellum there are also attached to the 

 end of the second joint two peculiarly-formed processes 

 or jointed hairs, which are almost certainly sense organs of 

 some sort, and are most probably olfactory organs. 



In general form the thorax forms a sort of six-sided box, 

 and is somewhat larger than the head in all dimensions. 



Although no sutures can be distinguished on its surface, 

 its division into its three component segments is sufficiently 

 indicated in its outline, and by three pairs of lateral tufts 

 of bristles, which are longer and stouter than those of any 

 other region of the body. The component hairs of these 

 tufts are all compound, each being clothed throughout its 

 length with filaments of considerable proportional length ; 

 and each tuft springs from a nipple-shaped tubercle, which 

 appears to be capable of a certain amount of voluntary 

 movement, though, from its position, it is obviously not 

 the rudiment of a leg. These tufts appear to act by way 

 of lateral keels, whereby the larva is maintained in any 



