232 INDIRECT BENEFITS DERIVED FROM INSECTS. 



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 despatch 

 it, and then, with incredible labour, carry it up to their nest. 

 Madame Merian, in her account of the periodical ants men- 

 tioned to you before, and which is confirmed by Azara', no- 

 tices their clearing the houses of cock-roaches and similar 

 animals ; and Myrmica omnivora is very useful in Ceylon in 

 destroying the former insect, the larger ant, and the white 

 ant.^ 



You are not perhaps accustomed to regard wasps and hor- 

 nets 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^ ; and probably in consequence of this 

 circumstance, flies in many places were so extremely numerous 

 as to be quite a nuisance. Keaumur 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 devourers of insects in their perfect state, 

 the manners and food of whose larvae we are unacquainted 

 with. St. Pierre speaks of a lady-bird, but it probably be- 

 longed to some other genus, of a fine violet colour, with a head 

 like a ruby, which he saw carry ofl* a butterfly.* Linne in- 

 forms us that Clerus formicarius devours Anohium pertinax, 

 A fly related to Panorpa communis appears created to instil 

 terror into the pitiless hearts of the tyrants of our lakes and 



1 Voyages, i. 1 85. 2 Percival's Ceylon, 307. 



3 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. 



4 St. Pierre, Voy. 72. 



