MOUTH OF GNATS AND FLIES. 15 



two tubes. At the point Avliere the tubular prolonga- 

 tion springs from the basal portion of the maxilla, 

 there is a very minute two-jointed palpus, which 

 sufficiently indicates the true nature of the organ. 

 The use of this beautifid spiral trunk needs no expla- 

 nation, for there can be few wdio have not observed 

 butterflies busily engaged in pushing their unrolled 

 tongues into the recesses of flowers in search of the 

 sweet juices which usually collect there. 



Very different from this elegant and harmless organ 

 is the formidable weapon with which the mouths of 

 the Gnats and many flies are armed, and which often 

 causes these insects, contemptible as they are from 

 their size, to rank amongst the greatest pests of the 

 countries where they abound. Beneath the heads of 

 these little creatures we find a tubular organ, which 

 is sometimes fleshy, and sometimes horny in its tex- 

 ture. In either case it is the representative of the 

 lower lip, and its tip is often furnished with a fleshy 

 disc formed of two lobes, which is constantly em- 

 ployed as an organ of touch, and is considered by 

 many entomologists as the representative of the labial 

 palpi. This tube or proboscis is cleft on its upper 

 surface, and within it we find, in the most perfectly 

 organized of these insects, five bristles or lancet-like 

 organs, some of which can be pushed out of the 

 sheath-like lower lip so as to Avound the skin of other 

 animals, when, by the combined action of the whole, 

 a sort of pump is produced, by means of which the 

 blood is sucked up into the body of the insect. Four 

 of these lancets represent the two pairs of jaws of the 

 biting insects, and one pair of them, representing the 

 maxillae, are even furnished Avith palpi, composed of 

 from one to five joints, which project from the base of 



