LIFE HISTORY OF THE BLUE CRAB. 109 
quite small. In the fall months some few are found about Crisfield and to the south- 
ward in Pocomoke Sound, but in general the number is insignificant. 
Practically all the young, then, are hatched in the southern part of the Bay. Sponge- 
bearing crabs begin to be fairly numerous during the last week of May. As seen in 
Table F, they are most numerous during the first two or three weeks of June. About 
June 15 to 20 the eggs begin to hatch. The bulk of the young are hatched from the 
middle of June to the middle of July. From then on a gradually decreasing number are 
hatched until about the first of September, after which time very few sponge-bearing 
crabs are found. 
The young at some time between hatching and reaching maturity migrate north- 
ward to such a distance that the majority of them are found from about the latitude 
of the Rappahannock River, Va., to Baltimore, Md. They are most numerous in 
Tangier and Pocomoke Sounds and the neighboring waters of the Eastern Shore of 
Chesapeake Bay, in Maryland. ‘This is, no doubt, due to the fact that the bottoms 
underlying these waters are extensively covered with sea grass and afford a very 
favorable ground for the molting process. 
The proof for the fact of the migration of the young lies in this point: Almost no 
sponge-bearing crabs occur in these northerly waters. Countless numbers of immature 
crabs do occur there and form the basis for an immense soft-crab industry, an industry 
which does not exist in the southern part of the Bay. 
As the young are found in these northern regions in vast numbers, but do not 
hatch there, they must have been hatched elsewhere and migrated to this point. The 
migration must have been made from the lower part of the Bay, since practically all of 
the sponge-bearing crabs are found there. 
At the opening of the season, from about April 15 to May 1, crabs measuring from 
1 to 2 inches in width are quite abundant in the vicinity of Crisfield, Md. So numerous 
are they that it has been found advisable to legislate against the catching of crabs 
measuring less than 3 inches in breadth. It is not probable that all these small crabs 
make the entire journey from the southern part of the Bay in the spring, but no doubt 
they have moved at least a part of the distance up the Bay during the preceding summer 
and autumn. It is not known what stage the young crabs are in either at the begin- 
ning or close of the migration. It may be that it is entirely completed during the first 
summer, possibly before the crab has finished the megalops stage. Or, on the other 
hand, it may not be undertaken until the crab stages are reached, and yet be completed 
before the close of the first autumn. However that may be, it is evident that the migra- 
tion is made. Wherever cold weather overtakes them the crabs lie on the bottoms 
until spring, when they again resume their activities. Moltings occur at intervals in 
the course of this migration. The crabs cease the northerly migration at latest by the 
time the maturity and mating periods are reached. ‘The fact that the sponge-bearing 
crabs are distributed over a region extending from the Capes to nearly the northern 
boundary of Virginia results in some of the young reaching more northerly points than 
others before attaining maturity. Observations carried out at various points on the 
Bay showed that the crabbing season opened later in the year the farther north the 
investigations were carried. 
The young crabs then reach maturity and mate in the waters just mentioned, 
which extend from about the latitude of the northern part of Virginia to Baltimore, Md., 
110307°—21——-8 
