Ban — The Biology of Stagmomantis Carolina. 5 



The Structure of the Egg-Case. 



Before taking up the details of the emergence and the 

 nymph forms, it will be well to get clear in mind the archi- 

 tecture of the nest from which they emerge. 



The egg-case is built by the mother mantis in the fall 

 and the old insect dies with the approach of winter. The 

 new organism hibernates in the egg-stage, amply pro- 

 tected in the ootheca. The number of individuals nor- 

 mally contained in one of these cases varies from 36 

 to 140. 



Photographs of 39 egg-cases (PI. XV) will give an ade- 

 quate idea of their general appearance and variation, 

 while PI. XVI shows the different sections and the details 

 of architecture. We can best appreciate this picture if we 

 imagine each egg-case to be a dwelling of many rooms 

 (cells), grouped into two rows of suites of four rooms, 

 each suite having a gallery which runs past the end of 

 each room. This gallery has an opening at the top, 

 through which the four occupants of the one suite emerge. 

 The eggs are deposited on end in the cells, and are in- 

 clined toward the opening, so that any of the insects can 

 emerge without disturbing the other occupants of the 

 ootheca or of their own particular suite. Of course two 

 insects cannot emerge from one suite at precisely the 

 same time, but one may follow promptly after the other 

 in single file, so very little interference occurs under this 

 system. This arrangement of the cells is clearly shown 

 in the cross-section, Fig. 7-8. The provision of separate 

 galleries and exits for every four insects seems a won- 

 derful economy of Nature. 4 Thus when common environ- 

 ment or common age brings all of the occupants of the 

 nest to maturity and ready for emergence simultaneously, 

 the probable high mortality resulting from crowding 

 around a common exit is avoided. This is why we can 

 examine an egg-case in the early morning and find not a 

 trace of life, return in fifteen minutes and find the top 

 literally teeming with struggling nymphs. Figs. 5 and 6 



* For the method of making the egg case, see p. 40. 



