INSECT. 



827 



cently discovered, that the manna which, it will be 

 remembered, served the Israelites for food during 

 their passage through the Wilderness, is but the con- 

 creted juice of an Arabian tree (Tamarix mannifera), 

 which is caused to flow by the puncture of a small 

 species of Coccus, which the celebrated Prussian 

 entomologist, Dr. Klug, has recently described and 

 figured under the name of Coccus manuiparus in his 

 splendid work upon the insects of Arabia, and to 

 whom the writer himself is indebted for specimens of 

 this interesting insect. In medicine insects are also 

 of great service. Of these the Canlharis vesicatoria 

 is the most important, and of the properties of which 

 an account will be found in our article CANTHARID^. 

 Numerous other species were formerly introduced 

 into the Pharmacopoeia, but they have gradually been 

 disused. In a commercial point of view, silk, chermes 

 and cochineal are some of the most important products. 

 Of the former we sliall give a detailed account in our 

 article upon the SILKWORM ; and of the latter a de- 

 scription has been published in our article COCCID^E. 

 There are many other insects which construct silken 

 cocoons, and emit various coloured dyes, and which 

 it might be very serviceable to endeavour to intro- 

 duce as well as the true silkworm of the coccus cacti. 

 Gumlac also, wax and ink-galls, are insect produc- 

 tions of too great importance to be passed over 

 without notice. But there are other classes of bene- 



The Ink-gall insect, and the insect by which it is produced. 



fits resulting from the relations of insects with other 

 organised beings. These, although less directly 

 affecting man, ought not to be overlooked in a 

 general survey of the economy of nature. Suppose 

 the race of insects to be entirely annihilated, and 

 then observe the thousands of ills which would in- 

 evitably result from the putrefying masses of animal 

 and vegetable productions, and which are now, as it 

 were, reduced to their native elements solely by the 

 interference of the insect tribes. The entire tribes 

 of Silpha, Necrophagi, Dcrmcatcs, Nilidulfs, immedi- 

 ately fall upon the dead carcasses of animals, devour- 

 ing the flesh, and accelerating the dissipation of the 

 putrid mass, and these, assisted by myriads of flies, 

 which deposit their eggs in the decomposing- body in 

 such immense numbers, succeed, in a very few days, 

 in reducing the carcass to a mere skeleton. In like 

 manner, the Geotrupidas, Histerida:, and many other 

 insects, are equally serviceable (as we have already 

 stated in our articles upon these groups) in dissemi- 

 nating the excrements of animals, and rendering them 

 srrviceable to the agriculturist ; whilst the tribes of 

 insects which feed upon decaying vegetable matter 

 are even still more numerous. As serving for food 

 to some of the higher animals, as fish, birds, some of the 

 smaller mammalia, &c., insects are eminently service- 

 able in the scale of the creation. Amongst birds, 

 the shrikes, and the genera Sylvidte, Motacilla, An- 

 thura, Certhia, Muscicapa, and Hirundo, as well as 



the cuckoos and pies ; and amongst quadrupeds, the 

 genera Stenops and OtoRcnus, which feed upon 

 grasshoppers, the bats, shrew, hedgehog, mole, and 

 especially the genus Myrmecophaga, which derive 

 their sole nutriment from insects. Many species of 

 insects are equally serviceable in destroying other 

 noxious insects. Of these the tribes of predaceous 

 beetles, sandwasps, ants, dragon-flies, spiders, &c. 

 are to be noticed, but more especially the larva? of 

 the ladybirds (Syrphidaa) and golden-eyed flies, which 

 destroy myriads of plant lice. All these, however, 

 yield to the Ichneumonidce, which annually destroy 

 more caterpillars than the whole tribes of insectivo- 

 rous birds. We must refer to our article upon this 

 family to show the almost universal dominion of these 

 parasitic tribes. In the last place, we have to notice 

 the great services rendered by insects in effecting the 

 impregnation of plants, in many of which the position 

 of the sexual organs is such, that, were it not for the 

 intervention of insects, especially bees, butterflies, &c., 

 which, whilst seeking food for their own nourishment, 

 inconsciously perform a most important office, of 

 of which we have already, in our article CECDOM.YIA, 

 mentioned an instance ; and in our article CYNIPID.E 

 we have noticed the effect of insects in effecting the 

 more rapid ripening of the fig, by the process termed 

 caprification by the inhabitants of the Levant. 



It is, however, necessary for us now to reverse the 

 picture, and to observe, that if insects are capable of 

 being serviceable to mankind, other species are not 

 less injurious to him and his property. We will first 

 notice such species as possess a direct influence 

 against mankind. Of these the various species of 

 lice, the flea, jigger, and the bed-bug, are pre-eminently 

 obnoxious. Besides these, we are condemned to 

 suffer from the occasional attacks of multitudes of 

 other species, which at all hours of the day cease not 

 their tormenting powers. Moreover, the hotter the 

 clime and the period when the body requires the 

 greatest portion of rest, the more numerous are the 

 hordes of our insect enemies. The Tabani, Stornoxes, 

 Asili, are all highly irritating ; but all these yield to 

 the gnat and the musquito, which are sometimes so 

 annoying and so numerous, that their victims have 

 sunk under their attacks. There is also another little 

 insect, which, in the autumn, is very annoying to 

 persons who walk about the fields, and which is so 

 minute that it escapes observation. It is called the 

 harvest-bug, but is in reality one of the Acandcs, of a 

 red colour, its mode of attack being to insinuate 

 itself into the flesh of the legs, where it causes an 

 intolerable itching, and raises the most irritating sores. 

 An analogous species inhabits the West Indies, 

 where surgical operations are required to dislodge it, 

 causing, if neglected, abscesses, gangrene, and even 

 death. The name of Scholcchiasis has been applied 

 to a disease in which the larvae of various species 

 of insects are found in the human body, but these 

 appear to be entirely accidental cases wherein these 

 larvse have been injected. A species of (Estrus, in 

 like manner, has been found to be parisitic within the 

 body of persons residing in the tropics, but this 

 (although it has received the name of CEslrus fwminis) 

 we should be rather induced to regard also as an 

 accidental locality selected by the insect, instead of 

 its real habitat. There is another tribe of insect 

 enemies whose attacks are not less annoying, although 

 not resulting, like the former, from a desire to feed 

 upon our bodies. Here are to be ranked the bees, 



