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Show 1897.] OF T H E LEGS IN T H E BLATT1D.E. 913 of sufficient space for running about, was the chief cause of this degree of mortality. That it was abnormally high seems probable, especially in view of the facts which will be mentioned later on, concerning the hatching of the egg-cases. Moreover, though Cockroaches once established in a building may become extremely numerous, their slowness in spreading in the neighbourhood is well known, and it is probable that we by no means understand what conditions are most favourable to this imported species. I succeeded, however, in maintaining a few individuals in health for nearly two years and one lived for rather over that time, and eventually escaped from confinement. Bread and cake were always readily eaten, but the animals seemed to pay no attention to a moist sponge always kept in the cages. With large numbers in one cage it was impossible to observe how often any one individual made a meal, but Dr. Sharp 1 has called attention to the very small amount of food that is required to maintain a Cockroach in good condition, and that many weeks of starvation seem to make little difference to the animal. In the case of m y own Cockroaches, a weak individual was never attacked by his companions, but the soft parts of the dead were soon devoured, as were all cast skins not removed from the cages. These latter were certainly not always eaten by their owners, though occasionally they were. Occurrence of the Ecdyses.-On this subject the monograph of Miall and Denny 2 coutains the following statement in quotation of Cornelius :i : - " The first change of skin occurs immediately after escape from the egg-capsule, the second four weeks later, the third at the end of the first year, and each succeeding moult after a year's interval. At the sixth month the insect becomes a ' pupa,' and at the seventh (being now four years old) it assumes the form of the perfect insect. The changes of skin are annual and, like fertilization and oviposition, take place in the summer months only. These statements are partly based on observations of captive Cockroaches, and are the only ones accessible ; but they require confirmation by independent observers, especially as they altogether differ from Hummel's account of the life-history of Blatta germanlca, and are at variance with the popular belief that new generations of the Cockroach are produced with great rapidity." The observation of H u m m e l 4 referred to is that Phyllodromla germanlca performs six ecdyses between April and September, and becomes adult within seven months from hatching out of the egg-capsule. M y own observations on the post-embryonic development of S. orientalis may now be described. In the first place great difficulty was experienced in obtaining i Cambr. Nat. Hist. v. p. 229. . . 2 ' The Structure and Life-history of the Cockroach (Periplaneta orientalis) (London, 1886), p. 23. . . . 3 'Beitrage zur naheren Kenntniss von Periplaneta orientalis. Elberteld, 4 '• Quelques observations sur la Blatte germanique." Essais Entomolo-giques. I. St. Petersbourg, 1821. |
