188 Annals Entomological Society of America [Vol. IV, 



before hatching, the embryo will be found with its head and pro- 

 thorax situated directly beneath the portion of the egg removed 

 (Fig. 1, h and p). The pressure exerted by the cervical ampulla 

 is, therefore, directly against the operculum. 



Hatching spines for the purpose of rupturing the embryonic 

 envelopes and also for breaking or cutting open the egg-shell 

 have been described from many insect eggs. Above the pro- 

 thorax of Diapheromera, the thin amnion is covered by num- 

 erous long spines which point toward the operculum. These 

 spines, like the egg-burster (or ruptor ovi as Riley (6) calls it) 

 of Corydalus cornutus, are portions of the amnion itself. If 

 the prothorax of a walking-stick is examined after its emergence 

 from the egg, no spines are found, but simply short blunt pro- 

 tuberances. In all probability, the long spines of the amnion 

 above the prothorax assist in rupturing the vitelline membrane 

 which is especially thick beneath the operculum. 



' ' When the young walking-stick is in the egg, ready to emerge, 

 the meso- and metathorax are not remarkably elongate, but 

 before the little creature is fairly out of its narrow prison, the 

 thoracic segments assume their usual proportions. It is said 

 to be a most curious sight by those who have observed this 

 almost instantaneous development." (Caudell [2]). 



An attempt was made by us to secure an explanation for 

 this curious phenomenon observed by Caudell. After the 

 chorion of the egg was removed, the embryo was found to be so 

 curled up in the egg that the posterior end of the abdomen lay 

 near the head region. A longitudinal section through the 

 embryo showed that the thorax was folded transversely in a 

 dorso- ventral direction (Fig. 2). In all probability it is simply 

 the straightening out of these folds as the young walking- 

 stick emerges, that causes the thoracic segments to assume their 

 usual proportions. If the pressure exerted by the cervical 

 ampulla at the time of hatching is not sufficient to rupture the 

 amniotic and vitelline membranes and also to throw off the 

 operculum, it may be possible that the straightening out of some 

 of these thoracic folds assist in the process. 



After pushing off the operculum, the young walking-stick, 

 with the prothorax bent down at its union with the mesothorax, 

 begins to emerge from the egg (Fig. 3). The cervical ampulla 

 is now slightly swollen, and the prothorax possesses a deep 

 green color, due to the blood which has accumulated within it. 



