INDIRECT BENEFITS DERIVED FROM INSECTS. 157 



in France by the name of Vinaigrier, is supposed to destroy more cock- 

 chafers than all their other enemies, attacking and killing the females at 

 the moment of oviposition, and thus preventing the birth of thousands of 

 young grubs. 1 Lastly come the Brachyptera, many of which prey upon 

 insects as well as on putrescent substances. Mr. Lehmann tells us that 

 some of them are very useful in destroying a weevil (Apion flavifemo- 

 ratum*), the great enemy of our crops of clover seed. 



Amongst the devourers of insects in their perfect state only, must be 

 ranked a few of the social tribes, ants, wasps, and hornets. The first- 

 mentioned indefatigable and industrious creatures kill and carry off great 

 numbers of insects of every description to their nests, and prodigious are 

 their efforts in this work. I have seen an ant dragging a wild bee many 

 times bigger than itself; and there was brought to me this very morning, 

 while writing this letter, an Elater, quite alive and active, which three or 

 four ants, in spite of its struggles, were carrying off. An observing friend 

 of mine 3 , who was some time in Antigua, informed me that in that island, 

 a kind of ant which construct their nests in the roofs of houses, when they 

 meet with any animal larger than they can carry off alive, such as a cock- 

 roach, &c., will hold it by the legs so that it cannot move, till some of 

 them get upon it and dispatch it, and then, with incredible labour, carry 

 it up to their nest. Madame Merian, in her account of the periodical ants 

 mentioned to you before, and which is confirmed by Azara 4 , notices their 

 clearing the houses of cockroaches and similar animals ; and Myrmica 

 omnivora is very useful in Ceylon in destroying the former insect, the 

 larger ant, and the white ant. 5 



You are not perhaps accustomed to regard wasps and hornets as of 

 any use to us ; but they certainly destroy an infinite number of flies and 

 other annoying insects. The year 1811 was remarkable for the small 

 number of wasps, though many females appeared in the spring, scarcely 

 any neuters being to be seen in the autumn 6 ; and probably in conse- 

 quence of this circumstance, flies in many places were so extremely nume- 

 rous as to be quite a nuisance. Reaumur has observed that in France 

 the butchers are very glad to have wasps attend their stalls for the sake of 

 their services in driving away the flesh-fly; and, if we may believe the 

 author of Hector St. John's American Letters, the farmers in some parts of 

 the United States are so well aware of their utility in this respect, as to 

 suspend in their sitting rooms a hornet's nest, the occupants of which 

 prey upon the flies without molesting the family. There are other de- 

 vourers of insects in their perfect state, the manners and food of whose 

 larvse we are unacquainted with. St. Pierre speaks of a lady-bird, but it 

 probably belonged to some other genus, of a fine violet colour, with a 

 head like a ruby, which he saw carry off a butterfly. 7 Linne informs us 

 that Clerus formicarius devours Anobium pertinax. A fly related to Panorpa 

 communis appears created to instil terror into the pitiless hearts of the 



1 Latr. Hist. Nat. x. 181. 



2 Linn. Trans, vi. 149. Kirby, Ibid. ix. 42, 43. 



5 The late R. Kittoe, Esq. 



4 Voyages, i. 185. Percival's Ceylon, 307. 



6 Mr. Knight made the same observation in 1806, and supposes the scarcity of 

 neuters arose from the want of males to impregnate the females. Philos. Trans. 

 1807, p. 243. 



7 St. Pierre, Voy. 72 



