326 



FOOD OF INSECTS. 



hearty meal of a putrid fungus. Ptinus Fur devours in- 

 differently dried birds or plants^, not refusing even tobacco ; 

 and from the impossibility that one of a million of the 

 innumerable swarms of gnats which abound in swampy 

 places, particularly in regions which but for them would be 

 lost to sensitive existence, should ever taste blood, it seems 

 clear that they are usually contented with vegetable aliment. 

 Indeed the males, as well as those of the horse-fly, of which 

 even the females readily imbibed the sugared fluid offered 

 to them by Reaumur never suck blood at all ; so that they 

 must either feed on vegetable matter, which in fact I have 

 observed them to do, or fast during their whole existence 

 in the perfect state. 



Though insects, generally considered, have thus a much 

 more extensive bill of fare than the larger animals, each 

 individual S23ecies is commonly limited to a more restricted 

 diet. Many both of animal and vegetable feeders are 

 absolutely confined to one kind of food, and cannot exist upon 

 any other. The larva of CEstrus Equi can subsist no where 

 but in the stomach of the horse or ass ; wdiich animals, 

 therefore, this insect might boast with some show of reason to 

 have been created for its use rather than for ours, being to 

 us useful only, but to it indispensable. The larvae of Scosva 

 Pyrastri, according to De Geer, eat no oih&c Aphis hwi that of 

 the rose.^ Most Ichneuraons and Sphecina prey each upon 

 a single species of insect only, which therefore they would 

 seem to have been formed for the express purpose of keeping 

 within due limits. Reaumur mentions having once found in 

 a parcel of decaying wood the nests of six different kinds of 

 the latter tribe, each of which was filled with flies of a 

 distinct species.^ Cerceris auritus and Philanthus IcEtus in 

 the larva state feed solely on the weevil tribe of Coleoptera, 

 the latter being restricted even to the short-rostrumed family, 

 as Otiorhynchus raucus, &c. ^ ; while Bembex rostrata, another 

 hymenopterous insect, selects flies, as Musca Ccesar, &c.'^ 



1 Reaum, iv. 280. 2 De Geer, vi. 112. 



3 Reaum. vi. 271.; and M. L. Dufour has recently described a species of sand- 

 wasp {Cerceris), which selects various species of Buprestis as the food of its 

 progeny, some of wliich are of the greatest rarity to collectors. 



4 Entomologische Bemcrkungen (Braunschweig, 1799), p. 6. 



° Latreille, Ohs. surles Hymenopteres. Ann. de Mas. xiv. 412. 



