OCR Text |
Show 1897.] OF THE LEGS IN THE BLATT1D.E. 915 The dates when ecdysis occurred indicated no relation wdth either age or sex, and the final ecdyses at which the adult condition commenced were distributed over the whole period iu the same ratio as those of still immature individuals. The statement by Cornelius, that the post-embryonic development of S. orientalis extends over several years, received distinct confirmation from my observations, though to a very imperfect extent, as the purpose for which the immature individuals were kept in captivity was not primarily connected with their life-history, and consequently they were usually removed and placed in spirit when they had completed a single ecdysis. With regard to the statement that an ecdysis is performed immediately on leaving the egg-case, I failed to observe the actual emergence of the young therefrom, though in several cases I examined them within twenty-four hours of their hatching out. With these I could find no trace of cast cuticles, nor did any ecdysis occur for a week succeeding the examination. It is quite possible, however, that ecdysis did occur almost simultaneously with hatching, and that the cuticles shed were speedily devoured, as the young of this species commence to feed within a few hours of hatching. As already mentioned, the four-jointed form of tarsus was found in young only *4 cm. in body-length, which appears, from measurements I have made, to be the length of newly hatched individuals. Whether or not such very young individuals could have lived long enough to suffer loss of a tarsus, perform ecdysis, and reproduce the lost part it is not possible to decide. As regards the statement that two further ecdyses are performed in the first year, I was able only to ascertain that individuals of less than half the adult size may cast their cuticle twice within five months. This observation was made on eleven individuals which performed an ecdysis in April or May. These were isolated from the others and were observed to again shed the cuticle on different dates between June 7th and August 21st. The body-length of these individuals ranged from *6 to *95 cm. after the second ecdysis noted (the mean length of an adult being 2*1 cm.). The shortest time between two ecdyses observed was forty-three days (April 25 th to June 7 th). More than two ecdyses were not observed in a single individual, even among the several which were kept in captivity for about two years. It is, however, quite possible that an ecdysis occurred occasionally without being detected, as during certain weeks the animals were looked at only every other day. So far as these observations go, it will be seen that they confirm the statement of Cornelius that the post-embryonic development of this species is relatively long. The Act of Ecdysis.-The mode of shedding the cuticle is described and illustrated by Miall and Denny1, to whose account it may be added that the whole process usually lasts for two or three hours, though sometimes the crumpled mass of cast 1 Op. cit. p. 32. |