258 FOOD OF INSECTS. 



juices of plants or of animals by means of an instrument of a construction 

 altogether different — a hollow grooved beak, often jointed, and containing 

 four bristle-formed lancets, which, at the same time that they pierce the food, 

 apply to each other so accurately as to form one air-tight tube, through 

 which the little animals suck up^ their repast ; thus forming a pump, 

 which, more effective than ours, digs the well from which it draws the fluid. 



A third description of insects, those of the order Diptera, 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 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 (Emyhis, 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 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 extremity, 

 and others serrated on one side. The flea, the spider, the scorpion, have 

 all instruments for taking their food of a construction altogether different. 

 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. Suffice it to say, that they all manifest the most consum- 

 mate skill in their adaptation to the purposes of the insects which are 

 provided with them, and which can often employ them not only as instru- 

 ments for preparing food, but as weapons of offence 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 different species of gad-flies, and the Ephe- 

 merse — insects whose history is so well known as to afford a moral or a 

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

 lime in the perfect state as to need no food. Indeed it may be laid down 

 as a general rule, that almost all insects in this state eat much less than in 

 that of larvae. The voracious caterpillar, when transformed into a butter- 

 fly, needs only a small quantity of honey ; and the gluttonous maggot, 

 when become a fly, contents itself with an occasional drop or two of any 

 sweet liquid. , 



While in the state of larvae the quantity of food consumed by insects 



' The mode, however, in which this is effected, in all insects furnished with a proboscis, 

 can scarcely be by suction, strictly so called, or the abstraction of air, since the air-vessels 

 of insects do not communicate with their mouths : it is more probably performed in part 

 by capillary attraction ; and, as Lamarck has suggested (Si/st. des Anim. sans Verttbres, 

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



