177] LIFE HISTORY OF GORDIUS AND PARAGORDIUS—MA Y 57 



So far as the parasitic forms are concerned, then, there is in literature 

 no evidence of any real difference in the number of males and females pro- 

 duced. It is merely necessary to explain the difference observed in case of 

 free living specimens. 



The results of Miihldorf have already been mentioned. In the collec- 

 tions of Gordius rohustus made during these investigations I have usually 

 obtained a slight predominance of females over males, only in a few small 

 collections was a predominance of males present. In the collection of 

 Paragordius varius made at Urbana the females were far more numerous 

 than the males. At Douglas Lake, however, the reverse was true. Most 

 of the collections made along the shore of the lake contained very few 

 females. 



The explanation must be sought in the behavior of the animals and not 

 in any real difference in the numbers of the two sexes. The specimens in 

 the older collections were obtained mostly accidentally and were either 

 specimens that had just left their hosts, or were in the act of migration, or 

 specimens that had not found a normal resting place. Since males are as a 

 rule more active than females and more seldom come to rest in secluded 

 places, as do females during the egg-laying period, it is but natural that 

 they were the ones most commonly obtained in random collections. The 

 results of Meyer are easily explained on this basis as he obtained his speci- 

 mens by collecting in open water or dredging at the bottom of ponds. In 

 those locations he would get nothing but migrating specimens, chiefly 

 males. Miihldorf made most of his collections in small bodies of water 

 where the females could not seclude themselves and he obtained no real 

 difference in numbers. My own collections of Gordius robustus were made 

 chiefly at the egg-laying habitats of the females and consequently there 

 was a slight predominance of females. Since in this species the males have 

 a habit of remaining for the greater part with the females the predominance 

 was not very large. This also explains why very few specimens of Gordius 

 rohustus are obtained in general collections. The males of Paragordius 

 varius are more active in nature and consequently very few of them were 

 taken at Urbana, but they are more frequently obtained in general collec- 

 tions. At Douglas Lake I did not succeed in finding the habitats of the 

 egg-laying females and as a result the females obtained were chiefly those 

 that had just escaped from their hosts. A few were obtained that had 

 settled down on grass near the shore to lay eggs. 



Nothing very definite can be said about the seasonal variations of the 

 Gordiacea as reported by previous workers. The present investigations 

 indicate that the seasonal distribution depends more on the life cycle of the 

 host than on the habits of the Gordiacea themselves. 



The egg-laying habits of the females and the possible protection of the 

 eggs by the adults require some further explanation. Villot (1874) des- 



