TABLE 1.

Brief description of the stages of early embryogenesis in B. mori.

Stage	Characteristics	Hours AEA
		N25	O25	O15
A	One nucleus in parthenogenetic eggs or 2 pronuclei in fertilized eggs can be detected in exceptional cases.	0	0	0
B	Up to 40 nuclei assembled in the anterior third of the egg, nuclei are widely separated and some divide within the yolk.	7	6–12	12–24
C	Nuclei occupy about half of the anterio-lateral egg surface where they migrate to the periphery and initiate cellularization.	11	6–12	24–36
D	Nuclei occupy entire egg surface and form cellular blastoderm that contains (1) small cells of presumptive germ anlage in the lateral and ventral egg surfaces; (2) Larger preserosa cells peripheral to the germ anlage; (3) primary yolk nuclei in egg interior.	14	12–24	36–48
E	Large gaps between serosa cells, the cells of future germ anlage become more densely packed and begin to sink.	23	24–36	48–60
F	The rudimental anlage is clearly distinguished from the extraembryonic cells. The serosa is nearly continuous.	26	24–36	>72
G	The short anlage is enveloped by serosa and is separated from the extraembryonic cells.	NA	48–60	>72

Hours indicate the approximate time of incubation after egg activation (AEA) when stages were reached in eggs incubated at 25°C (column N25 based on data published by Nagy et al. (1994) and column O25 based on our data) and in eggs incubated at 15°C (column O15).