FOOD OF INSECTS. 



333 



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 several 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 are extremely various. In some genera (^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 scimitar ; together forming 

 so keen an apparatus, that De Geer has seen an Asilus pierce 

 with it the elytra of a lady-bird ; and I have myself caught 

 them with not only an Elater and weevil, but even a Hister 

 in their mouths. In many horse-flies we find four ; two pre- 

 cisely resembling lancets, and two, even to the very handles, 

 buck-hafted carving knives. The blood-thirsty gnat has five, 

 some acutely lanced at the extremity, and others serrated on 

 one side. The flea, the spider, the scorpion, have all instru- 

 ments for taking their food of a construction altogether dif- 

 ferent. But it is impossible here to attempt even a sketch 

 of the variations in these organs which take place in the 

 apterous genera, and in many of the dipterous larvae. Sufiice 

 it to say, that they all manifest the most consummate skill in 

 their adaptation to the purposes of the insects which are pro- 

 vided with them, and which can often employ them not only 

 as instruments for preparing food, but as weapons of oflence 

 and defence, as tools in the building of their nests, and even 

 as feet. 



Some insects in their perfect state, though furnished with 

 organs of feeding, make no use of them, and consume no food 

 whatever. Of this description are the moth which proceeds 

 from the silk-worm, and several others of the same order; 

 the diflerent species of gad-flies, and the Ephemeras — insects 

 whose history is so well known as to aflbrd a moral or a simile 

 to those most ignorant of natural history. All these live so 

 short a time in the perfect state as to need no food. Indeed 



