September'!, 1894.] 



KNOWLEDGE 



197 



matter, which to us smells most foully, and if this be 

 so with what we call evil scents, the same may be true of 

 other kinds. It is not, therefore, a legitimate inference that 

 sweet scents are always possessed by insects as a means of 

 attraction, but that evil odours are a means of protection. 

 But, nevertheless, it may well be the case that the substance 

 which yields the odour may be of such an irritating nature 

 as to make both fragrant and malodorous insects un- 

 palatable. 



Two orders of insects are particularly noteworthy for 

 the odours that attend them — the Hemiptera,in one division 

 of which, viz., the Heteroptera, or dissimilar- winged bugs, 

 the majority are supplied with a more or less penetrating 

 and disagreeable smell, and the Coleoptera, or beetles, a 

 good many members of which exhale odoui'S, agreeable or 

 otherwise. Outside of these two orders we only meet 

 with occasional instances of odoriferous insects, such as the 

 cockroaches amongst the Orthoptera, the lacewing flies 

 amongst the Neuroptera, and the caterpillar of the goat 

 moth amongst the Lepidoptera. Mr. Robson thinks that 

 the female swifts, which are nearly related to the goat moth, 

 also have the power of exhaling a faint odour which is 

 attractive to their mates, and that the fluttering of their 

 wings which takes place while they are waiting for a 

 partner helps to disseminate the odour. 



Amongst the Hemiptera-Heteroptera, or bugs, there is 

 a wonderful uniformity about the nature of the scent, as 

 well as of the organs by which it is secreted. In almost 

 every instance amongst the scores of odoriferous species 

 we possess in this country, the odour resembles that of the 

 bed-bug, so that even in this respect there is a family 

 likeness which enables the entomologist at once to refer 

 them to their proper order. As a rule, the larger the 

 insect the more powerful the scent, but that is not 

 universally the case, and amongst the more delicately 

 constructed species, irrespective of size, the smell is often 

 so feeble as to be practically imperceptible to human 

 sensibilities, though of course it does not follow that it is 

 imperceptible to the more acute senses of the insects 

 themselves. The glands by which the fluid is secreted lie 

 on the under side in the central line of the body, and open 

 between the third pair of legs. The form of the orifice 

 and its surroundings varies in the different species, so 

 that it can sometimes be used for classificatory purposes. 



The larger, hard-bodied bugs, whose curious shape has 

 gained for them the popular name of "bishops' mitres," 

 often smell very strongly, and so penetrating and persistent 

 is the odour that if the substance stains the fingers, the 

 odour is difficult to eradicate, and clings to them even 

 after washing. If after touching them the finger be 

 applied to the tongue, a burning and very irritating 

 sensation is felt. Most of these larger species are not very 

 common with us ; they are met with on trees and bushes 

 of different kinds, and are to some extent indifferent as to 

 diet, feeding on the sap of trees or the blood of insects. 

 As they do not occur in large numbers together, their very 

 strong scent is hardly noticed untO one comes within two or 

 three feet of them, but then it is found to be very powerful, 

 and if the entomologist happens to have included one of 

 them in his net as the result of sweeping amongst long 

 herbage, he is sure to be made acquainted with the fact by 

 his nose, even if his eyes are not acute enough to single 

 out the offender at once from amongst the rest of his 

 captures. The smell of the bed-bug is also peculiarly 

 nauseous, though no doubt our disUke of the scent is in 

 this ease accentuated by the knowledge of the uncleanly 

 conditions which are indicated by the presence of the 

 insect. But the worst ofl'ender in the whole order is a field 

 species which is often to be met with in profusion amongst 



Fig. 14. — Leptop- 

 fefna dolobrata 

 (magnified two 

 diameters). 



grasses and other long herbage. It is called Leptopterna 



dolobrata ; the male (Fig. 14) is a very handsome 



insect, and differs a good deal from the female. It is long 



and narrow, very variable in depth of colour, but with the 



fore parts yellow marked with longitudinal 



black bands, and the upper wings orange 



variegated with dark streaks. The female 



is much paler, being greenish-yellow, and 



rarely has her wings fully developed. 



The scent of this insect is most sickening, 



especially that of the female, and I have 



passed by places where the air has been 



strongly impregnated with the smell, 



though the insects were not nearer than 



ten or twelve feet off, and many of 



them much further than that. It is 



hardly likely that an insect so nauseous 



can have many enemies. 



The evil repute of this order of insects 

 is to some extent redeemed by one 

 species, a sand- and heath-loving creature, 

 and no very distant relation of the 

 bed-bug itself. This insect (Coranus 

 subapterus) is very elegantly marked with a cool grey, 

 and smells strongly -with a fragrance which reminds one 

 of pears. It is exceedingly well protected by its great 

 similarity in colour to its surroundings, so that possibly 

 the smell in this case may be a guide to its mates as to its 

 whereabouts. 



Amongst the Coleoptera, or beetles, there are species 

 equally renowned for their scent. The beautiful green 

 tiger beetles, which are such attractive adornments of 

 sunny banks in early summer, exhale, when captured, a 

 powerful and very agreeable odour, something like that of 

 sweetbrier. Considering that the insects are fiercely car- 

 nivorous, this is perhaps hardly what was to be expected. 

 That scents such as this are indeed independent of the 

 nature of the food is shown again in the musk beetle, a 

 very large dark-green insect with extremely long antennte. 

 The smell of this creature is not unUke that of the tiger 

 beetle, and equally agreeable, but its food is totally difl'ereut, 

 for the larva is an inhabitant of tree trunks, the solid wood 

 of which forms its daily diet. Thus we have a predaceous 

 beetle and a wood-feeder producing similar agreeable 

 scents, while other members of the family to which the 

 musk beetle belongs, though of quite similar habits, are 

 devoid of smell altogether. 



In all the cases already noted the fluid secreted is so 

 extremely ■volatile that it is never seen to issue from the 

 insect, and its presence is only detected by the smell, but 

 in the cases now to be noticed the liquid is not so volatile, 

 and its emission is itself one of the most objectionable 

 features of the insect, even when the scent is not decidedly 

 disagreeable. The various species of ladybirds are well 

 known to emit from their mouth and other parts of the 

 body a yellow, oily, acrid liquid, which has a very strong 

 and disagreeable smell. This habit is paralleled, and in 

 some cases exceeded, by members of the Chrijsomelidir, or 

 golden apple beetles. The most noteworthy offender in 

 this group is a shining metallic blue beetle with red wing 

 covers, called Lina jiojnili. Its larva, which feeds on 

 poplar leaves, has two conical warts on the fore part of its 

 body, and two rows of smaller tubercles on the back and 

 down the sides, and fi-om all these warts, as well as from 

 the mouth and the joints of the legs, a horribly fcetid, 

 whitish fluid exudes when the creature is alarmed. Not- 

 withstanding the disgusting nature of these secretions, or 

 rather, perhaps, we should say because of this quality, they 

 were formerly considered to have valuable medicinal 



