22 Roosevelt Wild Life Bulletin 



places (figure 9) when the splashing of twenty to fifty boys or girls 

 in the water stimulated the leeches to great activity, seldom revealed 

 more than two or three swimming at a time. Receptacles placed at 

 the camps with instructions that all leeches caught be placed therein 

 rarely yielded more than three or four as a day's catch at any one 

 camp. By collecting generally along the shores usually fifteen or 

 twenty could be gathered in a morning. I have taken several times 

 that many in the same time in eastern Pennsylvania and elsewhere. 

 By direct observation, especially at marked stations of equal areas, 

 and by the use of the receptacles above mentioned, it was found that 

 the distribution in Carr Pond during the summer of 1919 was not 

 uniform. Few leeches were found in the newer part of the lake near 

 the dam. They were several times as numerous in the body of the 

 lake, and were especially plentiful about the shallows in the vicinity 

 of Globe (figure 5) and Kennedy Camps and in the small cove near 

 Mr. Herbert's shack (figure 8). It seemed evident that the lake had 

 been stocked from a nucleus in the original pond and that the leeches 

 had not yet attained their maximum numbers or moved freely into 

 the new part of the lake. 



Ecologically considered Macrohdella is a swamp rather than a 

 pond animal. Normally it is an inhabitant of the shallows and the 

 vicinity of the shoreline where land and water meet. It may be 

 found concealed under stones and logs, more especially those that lie 

 partly out of the water. Here when well fed it rests quietly, or 

 when hungry lies in wait for frogs, warm-blooded animals that enter 

 the water, or other prey (figure 13, A, B). Any disturbance of the 

 water such as is caused by a wading animal attracts them, partly 

 because of the mechanical disturbance which stimulates the tactile 

 organs and partly because of the animal emanations that stimulate the 

 organs of chemical sense. Advantage of this peculiarity is taken 

 in collecting them. On stirring up the bottom with one's bare feet 

 any leeches that happen to be in the neighborhood may soon be 

 observed swimming or creeping toward the place, and may be 

 allowed to attach themselves to the skin and be picked off. Anglers 

 quite often find one or more of them attached to catches of fish 

 which have been strung and placed in the water where their lashing 

 and bleeding serve as attractions. 



Observations through the summer make it quite evident that the 

 leeches are attracted by the bathers also. They congregate and 

 remain about the docks and beaches, concealing themselves in the 

 crevices of the woodwork or among the stones, and issuing at the 

 bathing hour. Complaints of attacks became somewhat more frequent 

 during the latter half of the summer and there appeared to be a cor- 

 responding decrease in their numbers at points elsewhere. Having 

 fed at the bathing places they become quiescent and remain. Con- 

 sequently they become concentrated at these places and there is a 

 relative decrease in numbers elsewhere, as suggested. This is prob- 

 ably due in part to the fact that they become more active with 

 increasing temperature and consequently move more freely as the 

 water warms. The period of greatest prevalence at the docks cor- 



