396 FOOD OF INSECTS. 



forming a pump, which, more effective than ours, digs 

 the weli from wliich it draws the fluid". 



A third description of insects, those of the order Di- 

 plera, comprising the whole tribe of flies, have a sucker 

 formed on the same general plan as that last described, 

 but of a much more complicated and varied structure. 

 It is in like manner composed of a grooved case and se- 

 veral included lancets ; but the case, although horny, 

 rigid and beak-like in some, is in others fleshy, flexible, 

 and more resembling the proboscis of an elephant, and 

 terminates in two turgid liplets : and the accompanying 

 lancets are themselves included in an upper hollow 

 case, in connexion with which they probably compose 

 an air-tight tube for suction. The number and form of 

 these instruments is extremely various. In some ge- 

 nera {Musca) there is but one, which resembles a 

 sharp lancet. Others {Empis, Asilus,) have three, the 

 two lateral ones needle-shaped, that in the middle like 

 a scymetar; together forming so keen an apparatus, 

 that De Geer has seen an Asilus pierce with it the 

 elytra of a Coccinella; and I have myself caught them 

 with not only an Elafer and Curculio, but even a HiS' 

 ier, in their mouths. In many Tahani we find four ; 

 two precisely resembling lancets, and two, even to the 

 very handles, buck-hafted carving-knives ''. The blood- 

 thirsty gnat has five, some acutely lanced at the extre- 

 mity, and others serrated on one side. The flea, the 

 spider, the scorpion have all instruments for taking 



their mouths : it is more probably performed in part by capillary attrac- 

 tion ; and, as Lamprck has sii.^gested, {Syst. des Aniin. sans Vcrlcbrcs, 

 p. 193.) in part by a succession of undulations and contractions of the 

 bides of the organ. 



» Plate VI. Fig, 18—19. " 1'late VII. Fig. 5. 



