MEANS OF DEFENCE OF INSECTS. 417 



stones, and in places that have not a free circulation of air, exhale a most 

 disagreeable and penetrating odour, which De Geer observes resembles that 

 of rancid butter, and is not soon got rid of. It is produced, he says, from 

 an unctuous matter that transpires through the body l ; but I am rather in- 

 clined to think it proceeds from the extremity. I have noticed that some 

 small beetles of the Omalium genus, for instance O. rivulare, and another 

 species that I once found in abundance on the primrose (0. Primuke K. 

 Ms.), especially the latter, are abominably fetid when taken, and that it re- 

 quires more than one washing to free the fingers from it. Every one knows 

 that the cock-roach (Blatta orientalis), belonging to the Orthoptera order, 

 is not remarkable for a pleasant scent ; but none are more notorious for 

 their bad character in this respect than the bug tribe (Geocorisfs), which 

 almost universally exhale an odour that mixes with the scent of cucumbers 

 another extremely unpleasant and annoying. Some, however, are less dis- 

 gusting, particularly Lygceus Hyoscyami, which yields, De Geer found, an 

 agreeable odour of thyme. 2 Several lepidopterous larvae are defended 

 by their ill smell ; but I shall only particularise the silk- worms, which on 

 that account are said to be unwholesome. Phryganea grandis, a kind of 

 May-fly, is a trichopterous insect that offends the nostrils in this way ; but a 

 worse is Clirysopa Pcrla, a golden-eyed and lace-winged fly, of the next 

 order, whose beauty is counterbalanced by a strong scent of human ordure 

 that proceeds from it. Numberless Hymenoptera act upon the olfactory 

 nerves by their ill or powerful effluvia. One of them, an ant (Formica 

 fcetida De Geer,fcetens Oliv.), has the same smell with the insect last men- 

 tioned. 3 Our common black ant (F.fuliginosa), whose curious nests in 

 trees have been before described to you, is an insect of a powerful and 

 penetrating scent, which it imparts to every thing with which it comes in 

 contact ; and Fabricius distinguishes another (F. analis Latr., fastens F.) 

 by an epithet (fcetidissima) which sufficiently declares its properties. Many 

 wild bees (Andrena) are distinguished by their pungent alliaceous smell. 

 Crabro U-JJavum, a wasp-like insect, is remarkable for the penetrating and 

 spirituous effluvia of ether that it exhales. 4 Indeed there is scarcely any 

 species in this order that has not a peculiar scent. Some dipterous in- 

 sects though these in general neither offend nor delight us by it are 

 distinguished by their smell. Thus Mesembrina mystacea, a fly that in its 

 grub state lives in cow-dung, savours in this respect, when a denizen of the 

 air, of the substance in which it first drew breath. 5 And another (Sepsis 

 cynipsea} emits a fragrant odour of beaum. 6 I have not much to tell 

 you with respect to apterous insects, except that lulus terrestris, a com- 

 mon millepede, leaves a strong and disagreeable scent upon the fingers 

 when handled. 7 Most of the insects I have here enumerated, probably are 

 defended from some enemy or injury by the strong vapours that exhale 

 from them ; and perhaps some in the list produce it from particular or- 

 gans not yet noticed. 



I shall next beg your attention to those insects that emit their smell from 



1 iv. 86. 



2 De Geer, iii. 249. 374. 3 ibid. iii. 611. 



4 Kirby, Mon. Ap. Angl. i. 136. note a. 



5 De Geer, vi. 134. Meigen, Dipt. v. 12. 



e De Geer, vi. 135. 33. 7 ibid. vii. 581. 



E 



