Fig. 6.—Young nymph (male). × 6.
Fig. 7.—Older nymph (male) with rudiments of wings. × 2 1/2.
The antennæ of the male nymph resemble those of the adult female. Wings and wing-covers appear first in the later larval stages, but are then rudimentary, and constitute a mere prolongation of the margins of the thoracic rings. Cornelius says that the round white spot internal to the antenna first appears plainly in the pupa, but we have readily found it in a very young larva. The Insect is active in all its stages, and is therefore, with other Orthoptera, described as undergoing “incomplete metamorphosis.” After each moult it is for a few hours nearly pure white. Of the duration of life in this species we have no certain information, and there is great difficulty in procuring any.
Sexual Differences.
Male Cockroaches are readily distinguished from the females by the well-developed wings and wing-covers. They are also slighter and weaker than the females; their terga and sterna are not so much thickened; their alimentary canal is more slender, and they feed less greedily (the crop of the male is usually only half-full of food). They stand higher on their legs than the females, whose abdomen trails on the ground. The external anatomical differences of the sexes may be tabulated thus:—
| Female. | Male. |
| Antenna shorter than the body, the third joint longer than the second. | Antenna rather longer than the body, the third joint about as long as the second. |
| Wings and wing-covers rudimentary. | Wings and wing-covers well developed. |
| Mesosternum divided. | Mesosternum entire. |
| Abdomen broader. | Abdomen narrower. |
| Terga 8 and 9 not externally visible. | Terga 8 and 9 externally visible. |
| The 10th tergum notched. | The 10th tergum hardly notched. |
| The 7th sternum divided behind. | The 7th sternum undivided. |
| The external outlet of the rectum and vulva between the 10th tergum and the 7th sternum. | The outlet between the 10th tergum and the 9th sternum. |
| No sub-anal styles. | Sub-anal styles. |