The Common Cockroach, now so abundant, is not a native, but an importation from Asia; though how it reached this country is not quite certain, probably by way of Holland. It seems to have established itself in London by the end of the sixteenth century, and some two hundred years later we find Gilbert White recording (in or before 1790) that ‘a neighbour complained that her house was overrun with a kind of black beetle, or, as she expressed herself, with a kind of black-bob, when they got up in the morning before daybreak. Soon after this account I observed an unusual insect in one of my dark chimney closets, and find since, that in the night they swarm also in my kitchen.... The male is winged, the female is not, but shows something like the rudiments of wings, as if in the pupa state.... They are altogether night insects, lucifugae, never coming forth till the rooms are dark and still, and escaping away nimbly at the approach of a candle.’
This description leaves no doubt as to what the ‘black-bobs’ really were. This name seems to have dropped out of use, and it would be well if ‘black beetle,’ in the sense of Cockroach, were also allowed to drop, for the term contains just as many errors as words.
We may make our first acquaintance with these insects by keeping some specimens in confinement. A tin box, with a glass lid, will make a capital dwelling for them. Some paper should be put in, for them to hide in away from the light, and there can be no difficulty in providing them with food. ‘Bark, leaves, the pith of living cycads, paper, woollen clothes, sugar, cheese, bread, blacking, oil, lemons, ink, flesh, fish, leather, the dead bodies of other cockroaches, their own cast skins and empty egg-capsules, all are greedily consumed. Cucumbers, too, they will eat, though it disagrees with them horribly[16].’
We have Dr. Sharp’s authority for the statement that in confinement these insects are rather amusing pets, as they ‘occasionally assume most comical attitudes, especially when cleaning their limbs. This they do somewhat after the fashion of cats, extending the head as far as they can in the desired direction, and then passing a leg or an antenna through the mouth; or they comb other parts of the body with the spines on the legs, sometimes twisting and distorting themselves considerably in order to reach some not very accessible part of the body[17].’
The prejudice against these insects is, however, so strong, that most people will prefer to examine dead rather than living specimens, on account of the disagreeable odour of the latter. This odour is due to a fetid excretion from the mouth, and if the specimens are killed by dropping them into boiling water, this will be discharged, and after a little while they may be taken out with a pair of forceps, and put into spirit for preservation. If they are dropped alive into spirit, the excretion will communicate its strong scent to the preserving medium, and this should be changed before the insects are examined.
From Fig. 32 we may get a general idea of the appearance presented by a male or female, lying back upwards in a small glass dish, ready for examination with the pocket lens. The female may be distinguished at a glance by her wingless condition—only rudiments of wing-cases being present, and no wings—and her broader abdomen. In life she does not stand so high upon her legs as does the male, and her abdomen trails along the ground. The male does not acquire his wings till the last moult.
Female.Male.
Fig. 32.—Cockroaches.
As the Cockroach lies back uppermost in a glass dish, the head is almost concealed. This is especially the case, unless the insect is flattened out in some way, or pinned down to a piece of weighted cork. There will thus be, apparently, two, instead of three main divisions. This arises partly from the fact that the head is deflexed, or bent down so that the mouth is turned towards the rear, and partly because the first segment of the thorax bears a chitinous shield, roughly semicircular, which covers so much of the head as would otherwise be visible.