FOOD OF INSECTS. 223 
can be cither united into an air-tight canal, or be instantly separated, at the 
leasure of the insect. 
Another numerous race, the whole of the order Hemiptera, abstract the 
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 
Jancets ; 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 them- 
selves 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 (JZusca) there 
is but one, which resembles a sharp lancet. Others (mpis, 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 batpebinds and [have myself caught them 
with not only an Elater and weevil, but even a ister 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 impos- 
sible 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 consummate skill in their 
adaptation to the purposes of the insects which are provided with them, 
and which can often employ them not only as instruments 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 orler; the different species of gad-flies, and the Ephe- 
Mere — insects whose history is so well knownas to afford a moral or a 
simile to those most ignorant of natural history All these live so short 
atime in the perfect state as to need no food. Indeed it may be laid down 
asa general rule, that almost all insects in this state eat much less than 
1 Vor a full description of this instrument, see Reaum. i, 125, &e. 
2 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 pro- 
ably performed in part by capillary attraction: and, as Lamarck has suggested 
(Syst. des Anim. sans Verlébres, p. 193.), in part by a succession of undulations and 
Contractions of the sides of the organ. 
