304 Lake Maxinkuckee, Physical and Biological Survey 



III. The Odonata. Dragon-flies and Damsel-flies. 



Treatment of the species of this order in their relation to fish- 

 life will be found in the chapter of this report (p. 648) giving a 

 systematic list of the species of Dragon-flies and Damsel-flies known 

 to occur in the vicinity of Lake Maxinkuckee. 



Leeches 



These are found in great numbers everywhere around the lake, 

 and it is safe to say that there is not a species of fish that does not 

 suffer from their ravages. They are frequently found on mussels 

 also, as well as on turtles, crawfish, and mud-puppies. And they 

 do not refrain from attacking cattle and even human beings while 

 wading through the eel-grass near the shore. 



They often congregate in considerable numbers upon some ani- 

 mal which has been subjected to adverse conditions and make it 

 so much the harder for it to recuperate. Fifty-three specimens of 

 Glossiphonia parasitica were taken from the neck of a snapping 

 turtle whose shell was only seven inches long. The turtle was 

 fairly clean when caught but had been kept for ten days in a fish- 

 car with several others of its kind. 



The leeches are more abundant at certain seasons than at 

 others, especially in the spring, and there can be no doubt that they 

 at least contribute to the killing of the fishes, which perish in such 

 numbers at that season. 



They constitute therefore a serious menace to the fishing inter- 

 ests ; once let them get the upper hand and they would destroy the 

 fish rapidly. Hence it is of interest to ascertain what keeps them 

 down and prevents their multiplication in sufficient numbers to 

 prove destructive. 



No study of this problem has ever been published so far as 

 known ; indeed, but very few papers have appeared upon American 

 leeches, and they are concerned entirely with morphology and 

 systematization. The most that can be done here is to call atten- 

 tion to the importance of the study and record a few observations. 



Leeches lay their eggs in cocoons which are either deposited in 

 moist earth or glued to some object in the water. In one or two 

 genera the cocoon is covered by the body of the parent, who fur- 

 ther cares for the brood by carrying them about with her for some 

 time after they have hatched. But usually on hatching the young 

 seek the shelter of the algse and water plants in the shallow water 

 along shore. From this shelter they emerge to fasten upon what- 

 ever host they may select. 



