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, lie says, from 
an unctuous matter that transpires through the body’; 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 (O. Primule 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 (Geocorise), 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 Lygeus Hyoscyami, which yields, De Geer found, an 
agreeable odour of thyme.?— Several lepidopterous larve 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 Chrysopa Perla, 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 
felida De Geer, fetens Oliv.), has the same smell with the insect last men- 
tioned. Our common black ant (2. 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., fatens FP.) 
by an epithet ( fetidissima) which sufficiently declares its properties. Many 
wild bees (Andrena) are distinguished by their pungent alliaceous smell. 
Crabro U-flavum, a wasp-like insect, is remarkable for the penetrating and 
spirituous effluvia of ether that it exhales.* 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.2 And another (Sepsis 
cynipsea) emits a fragrant odour of beaum.°—TI have not much to tell 
you with respect to apterous insects, except that Zulus terrestris, a com- 
mon millepede, leaves a strong and disagreeable scent upon the fingers 
when handled.?_ 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 
liv, 86. 
2 De Geer, iii, 249. 374. § Ibid, iii, 611. 
4 Kirby, Mon. Ap. Angl. i. 136. note a. 
5 De Geer, vi. 154. Meigen, Dipt. v. 12. 
§ De Geer. vi. 185, 33, 7 Thid. vii. 581, 
EE 
