LIFE HISTORY OF THE BLUE CRAB. 405 



observed with reoard to these two forms among the females, that the 

 first, or virgin form includes all the smaller individuals, while the 

 second, or ovigerous form includes only those of larger size. That the 

 condition is not an evidence of age, however, will be shown further on. 



Crabs ma}" be found i^airing at almost an}" time during warm weather, 

 but there seem to be live or six periods between early June and the 

 beginning of cold weather when the act is at its height. During these 

 times mated crabs, " doublers," as they are called by the fishermen, are 

 found in considerable numbers, either lying on the bottom in shallow 

 water or swimming at the surface. It appears that the male crab is 

 able to distinguish the female which is about to shed her shell, and 

 having found such a one seizes her and carries her about with him, 

 sometimes for a day or two, until the shedding of her shell is immi- 

 nent. He then places her in some sheltered place and stands guard 

 over her ready to repel the advances of any other male. At this time 

 the female invariably is of the virgin form, and copulation has not 

 taken place. When she sheds her shell, however, she has passed into 

 the ovigerous form, the broad semicircular abdomen of her new con- 

 dition having been withdrawn from the shell of the narrow triangular 

 abdomen of the virgin form. She is now ready for copulation, and is 

 immediately approached again by her mate. She turns back her 

 abdomen, thus exposing the openings of her oviducts, the verges of 

 the male are inserted, and she is grasped by the tips of his second, 

 third, and fourth pairs of legs, and carried away. In the mated crabs 

 the female, before she has cast her shell, is carried by the male with 

 her back against his ventral surface; during copulation her position is 

 reversed. Copulation lasts for a day or two, coming to an end as 

 soon as the new shell of the female has hardened. The pair then sepa- 

 rate, and so far as is known pay no further attention to each other. ^' 



The female is now ready to produce her eggs, and for this act it 

 seems that she seeks the ocean or the mouth of some large bay. In 

 Chesapeake Bay mating crabs are abundant at least as far north as 

 Annapolis, but a crab with eggs is very seldom found there. On the 

 other hand, at Cape Charles City, Va., at Hampton, Va., and neigh- 

 boring points, egg-bearing females are far more abundant than either 

 males or virgin females during the latter part of summer, but appar- 

 ently do not often come into shallow water. All the individuals seen 

 at the two Virginia localities had been caught on trot lines. An exactly 



"Although the facts cited in the last few paragraphs are matters of common 

 knowledge among the crab fishermen, I am not aware that their relation has been 

 recorded in any of the printed accounts of this animal. The fact that copulation is 

 possible only while the female is in the soft-shelled condition has been noted by 

 several observers, and that about the time of copulation she changes from the narrow 

 abdomened to the broad abdomened form is mentioned on page 369 of Miss Rath- 

 bun's paper. 



