report that drills may be carried long distances on crabs, especially the hermit 

 crab, onto which they crawl to feed on the encrusting gastropods., crustaceans, and 

 other sessile animals. Stauber (1943) reports similar observations. 



Haskin(1937) in his intertidal migration studies had ample opportunity to 

 observe the activities of the common hermit crabs, Jagurus longicarpus and P 

 p ollicaris, in transporting Urosalpinx . He notes that in regions where these crabs 

 are so numerous as m Delaware Bay the role that they play in distribution of drills 

 is probably a significant one. On two separate occasions he found five marked 

 Urosalpinx attached to the shell of a Polinices occupied by a Pagurus pollicaris . 

 In several instances drills were found clinging by their pedal surfaces to shells 

 no bigger than their own inhabited by actively moving hermit crabs In numerous 

 cases hermit crabs occupying marked drill shells were found some distance from 

 the site of release of the drills; the possible role of the crabs in killing the snails 

 is not indicated. In one case a marked drill was found on the shell of a large hermit 

 crab 12 feet from the site of liberation 15 minutes after release . In an extreme case 

 Haskin recovered one marked drill, dead but still entire, being dragged over the 

 bottom by four small hermit crabs 150 feet from the stake where it had been placed 

 10 hours before. J. R. Nelson (pers . com.) has picked up horsefoot crabs ( Limulus 

 polyphemus ) carrying as many as 140 drills per animal. How common such unusual 

 cases of phoresis are is not known. 



Young drills may also be distributed by the current when they creep onto 

 floating algae and debris (Fedenghi, 1931c; Stauber, 1943). J. R. Nelson (pers, 

 com.) from years of observations in the coastal waters of the northeastern states 

 writes that tidal currents are of great importance in the dispersal of young drills 

 o.i inert objects that come to rest on the bottom at slack water and move when the 

 current reaches sufficient velocity. He notes that areas like Fireplace, Gardiners 

 Bay, Long Island, and Delaware Bay possess tidal currents of such velocity that 

 such objects are doubtless transported several miles in a single tidal period. This 

 v/ould account for the rapid migration several miles upbay into normally drill free 

 areas which he observed in Delaware Bay following the dry years of 1930 and 1931 . 

 T. C. Nelson (pers. com.) observed the transport of newly hatched Urosalpinx on 

 Zosi.era floating in a tidal stream over a distance of at least 40 feet. He notes 

 that young drills are strongly negatively geotactic hence would be transported on 

 any material carried along the bottom . 



On the basis of this review the writer tentatively supports the conclusions 

 of Fedenghi and Staubei that the bulk of the drill population moves about to a 

 rather limited degree, particularly over oyster bottoms; occasional exceptions 

 may be explained on the basis of phoresis. Haskin's interesting observation on 

 the decline of locomotory rate of fastest moving liberated drills to the group level 



97 



