176 ARTHUR M. BANTA. 



is most certain to be dislodged by the vigorous kicks of the other. 

 If however a second male, as rarely happens, succeeds in getting 

 well beneath the first so as not to be readily reached with the 

 latter's hind legs the first male is very likely to be pushed upward 

 and away from the female's body except for the clasping fore 

 legs. In such a case he soon releases his hold. Amid the great 

 preponderance of males the most vigorous and active ones are 

 more likely to secure mates and to keep possession of them and 

 effect fertilization of the eggs. 



The female when in copulo does not so generally remain be- 

 neath the water as when unpaired, though much the greater part 

 of the time is still spent upon the bottom or on submerged brush. 

 It is possible of course that when a certain physiological state 

 supervenes the female remains more at the surface than pre- 

 viously and this subjects her to the attacks of the males so that 

 she does not long escape a mate, and that the pairing female 

 does not remain more at the surface than she would if no male 

 found her. It is certain that whereas the unpaired females are 

 not rarely seen momentarily at the surface they very rarely re- 

 main for even a few seconds. The female is generally con- 

 siderably larger than the male and is able to swim about readily 

 with the smaller male upon the back. The male sometimes aids 

 in swimming but usually remains passive regardless of the move- 

 ments of the female. When approached by another male how- 

 ever the pairing male makes a vigorous defence with the hind 

 legs and this with the struggles of the female usually serves to 

 dislodge the intruder. But the struggles of the female and the 

 resistance of the male are not always successful in warding off 

 a second male. In the height of the pairing season there is 

 usually to be seen one or more cases of more than one male 

 clasping hold of a female. Such a multiple copulation is fraught 

 with danger to the female as well as to the more successful 

 males. There is a constantly recurring struggle on the part of 

 the rival males for possession of the female. Unless the female 

 is able to leave and remain beneath the surface these struggles 

 are certain to attract other males which also attempt to get 

 possession of the female. The result is a struggling, writhing 

 mass of males holding on to the female and to the males already 



