LIFE HISTORY OF THE BLUE CRAB. 125 
SUMMARY. 
The following is a list of the main points brought out in this report: 
1. The blue crab, Callinectes sapidus, is found in the salt and brackish waters of 
the Atlantic coast from Massachusetts to South America. 
2. The young hatch from eggs borne for about 15 days upon the swimmerets of the 
abdomen of the female in a mass called a sponge. There are about 1,750,000 eggs in 
one sponge. 
3. The young do not cling to the swimmerets of the mother after hatching. They 
do not devour the mother as they are hatched, as supposed by some. 
4. The young, after hatching, increase in size only when they molt. They pass 
through two stages before reaching the true crab shape. In the first, or zoéa stage, 
molting occurs four or five times; in the second, or megalops stage, probably only once. 
About one month is required to complete these two stages. 
5. In passing from the megalops stage to that of the adult-crab stage about 15 
moltings occur. The average time between molts is 15 days, ranging from 6 days for 
the early stages to about 25 for the last. The average increase in width at each molt 
is one-third. 
6. The crabs mature and mate during the second summer, at the age of 12 to 14 
months. 
7. The female reaches a molting at which the abdomen changes from a triangular 
to a broad, rounded form. This is most probably the last molting. The male, also, 
probably does not molt after reaching maturity. 
8. Molting is described. The crabs become hard again within two or three days 
after molting. Neither the tides nor the moon have any effect upon the molting 
process, although the tides do affect the distribution of the crabs. 
9. Juvenile crabs possess the power of regenerating an appendage which has been 
lost or voluntarily thrown off. Regeneration is completed at molting, but it is not yet 
known whether it occurs in the adult crab, which most probably does not molt. 
10. The young of the crabs of Chesapeake Bay hatch in the lower part of the Bay 
during June and July, migrate northward, mature in Maryland waters the next sum- 
mer, mate there during July and August, then the females move southward in the fall, 
and pass the winter on the bottoms in the southern part of the Bay. They spawn the 
following spring and summer. The males remain for the most part in more northerly 
waters. 
11. Mating occurs in the female at the time of the last molting, while she is yet 
soft. She is carried by the male for a few days prior to such molting, after which 
copulation is effected. At this time sufficient spermatozoa are implanted in the sperm 
sacs of the female to fertilize all the eggs which she lays during her lifetime. Fertiliza- 
tion is effected in the sperm sacs of the female. The ovaries of the female are very 
small at the time of the last molting, but begin to develop then, whether or not copu- 
lation occurs. If mating occurs quite early in the season, the eggs are laid within about 
two months. In the great majority of cases, however, mating occurs in July or August 
and the eggs are not laid until the following spring or summer. 
12. Practically all the female crabs found on the bottom of the southern part of 
the Bay are filled with eggs and will spawn the following season. This was amply 
110307°—21——9 
