142 ZOOLOGY. 



of flies which destroy vegetables, and their size is so graduated that they 

 are capable of destroying larvte of all sizes, from those several inches in 

 length, to such as do not exceed one twenty -fifth of an inch. 



Insects in their various states constitute the food of many beasts, birds, 

 reptiles, and fishes. Some, as the large grasshoppers, are sometimes dried 

 and eaten in the Levant ; some savage nations eat the large grubs found in 

 rotten wood ; and the cossus, which the ancients esteemed as a great deli- 

 cacy, was a larv^a of some kind, and an allied one is now eaten in Brazil. 

 Ants are eaten by the savages of Brazil, the formic acid probably replacing 

 the vinegar used in civilized gastronomy ; whilst some of the lowest savage 

 tribes devour their own vermin. 



The various species of blistering flies are employed under the name of 

 canfhaHdes ' the genus Coccus furnishes the beautiful dyeing material 

 cochineal ; the galls formed on oak trees by insects of the genus Cynips^ 

 are used in the arts ; and insects funiish honey, silk, and manna. 



Caprification is an art which has been practised from a remote period. 

 It consists in causing figs to ripen by suspending upon the trees branches 

 of the wild fig tree (named caprificus by the Romans), which is infested by 

 an insect which pierces the fruit and causes it to ripen. 



The indigenes of Brazil have made a curious surgical application of ants, 

 many of which, when they attack with their mandibles, will allow them- 

 selves to be pulled to pieces rather than let go. When one of these natives 

 has received a cut, the sides of the wound are brought together carefully, 

 and an ant adapted for the purpose is made to bite the conjoined edges, 

 when the body is torn from the head, the process being repeated according 

 to the length of the wound, so that the natives are often seen with rows of 

 ant heads upon various parts of the body. 



Although insects are essentially terrestrial, there are families, the mem- 

 bers of which swim upon the surface (as Gyrinus\ or walk with the body 

 raised above it (as Gerris^ or JTydrometra)^ the tips of their feet touching 

 the surface, and a few wliich walk uj)on the bottom (as jVepa). These are 

 almost entirely confined to the fresh waters. Westwood, however, describes 

 a genus {Micndymma) which inhabits the coasts of the sea between higli 

 and low water mark, under such circumstances that it must remain four hours 

 under water at each tide, and he mentions other instances of Coleoptera 

 remaining beneath salt water for shorter periods. (Mag. Zool. and Bot. ii. 

 12i.) According to Audouin, a small carabideous insect, Aepusfulvescens, 

 passes a great part of the time beneath the sea, holding a small quantity of 

 air among the bristles with which it is in part clothed ; but whether it can 

 abstract oxygen from the water when this is exhausted, has not been deter- 

 mined. It is probable, however, that this power exists in the coleopterous 

 genus Elmis^ and some allied ones, the species of which are small, tardy in 

 their movements, and unable to swim. They live affixed to stones at the 

 bottom of fresh waters, which are sometimes so rapid that the insects could 

 not reach the surface and return to the position in which they are found. 



Among the insects which walk upon the water, the most remarkable is 

 the genus Ilalobates (allied to Gerris)^ which is found far at sea in the 

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