REPORT OF THE STATE ENTOMOLOGIST I9IO 9/ 



the large, white mother larvae, by a great increase in the ecto- 

 derm, accompanied by its folding and extension anteriorly around 

 the posterior extremity, the development of the large lobes an- 

 teriorly and its segregation into somatic masses, indistinctly show^n 

 on plate 2y, figure 2, and apparently producing a peculiar cuboidal 

 aspect illustrated on plate 28. The greatly developed mesoderm in- 

 cludes a series of large, cuboidal cells, some at least probably being 

 the polar cells, and a certain portion destined to develop into a 

 much more conspicuous mass to be described later. These changes 

 are accompanied by a shrinking of the embryo from the extremi- 

 ties of the amniotic sac and the development of the digestive sys- 

 tem by an invagination from both extremities. This latter is in- 

 dicated in living embryos of young yellowish larvae, by the forma- 

 tion of irregular lobes at each extremity and the appearance in 

 the region of the sixth to the twelfth segments, of a considerable 

 mass of large-celled tissue, occupying most of that portion of the 

 body cavity and which we believe to be mesoderm (pi. 35, fig. 2) 

 and identical with that mentioned above. The changes from now 

 on are rapid. This conspicuous mass of mesoderm gradually be- 

 comes absorbed or reorganized into organs such as the digestive 

 system, its appendages and especially the ovaries, while the de- 

 veloping adipose tissue expands, occupies more space and pro- 

 duces a three-rowed appearance in the embryo (pi. 35, fig. 3). 

 Development of the head now proceeds, the mouth parts become 

 more definite, the ocular spot visible and the lobes at the posterior 

 extremity become well defined. Motion may be observed in the 

 embryo and shortly it is ready to escape from the mother larva. 

 The length of the fully developed embryo is about i mm. It is 

 frequently nearly as long as the small, yellow mother larva and 

 approximately half as long as the large, white larva. 



The development of the embryo reacts upon the mother larva 

 and she soon assumes a rather characteristic quiescent form, un- 

 doubtedly an outcome of her lowered vitality due to the rapid ab- 

 sorption of nourishment by the young. This results in the relax- 

 ing of the muscles, especially the transverse girdling bands at the 

 margins of the segments. The change in the condition of the 

 mother is probably explainable solely upon physiological grounds. 

 The time elapsing between the assumption of the quiescent stage 

 by the mother larva and the escape of the young is about seven 

 days. The first part of this period the embryos rarely exhibit signs 

 of life, though distinct motions of the head and anterior segments 



