4 PKOCEEDINGS OF THE NATIONAL, MUSEUM. vol. CO 



the life history Heider gave merely the oogenesis, with nothing on 

 the larval development. Heider's remarkable description has served 

 as a basis for the present paper, and with it have been compared 

 the morphology of DichelesthiuTn^ Nemesis^ and Eudactylina. 



ECOLOGY. 



While the component genera and species of the present family 

 are fixed parasites in the sense that they do not move about freely 

 over their hosts like the Caligidae and Argulidae, they are not abso- 

 iiitel}'' incapable of motion like the Lernaeidae. Consequently while 

 there is a greater or less loss of the powers of locomotion there is 

 no marked sexual dimorphism, the body frequenth'^ retains its seg- 

 mentation and flexibility, and none of the appendages are lost or 

 abnormally transformed. 



Sexual diTnorphism. — There is more or less disparity in size be- 

 tween the two sexes, but the general body structure remains the 

 same, so that the male of any genus can be easily located through its 

 resemblance to the female, and while the males are always smaller 

 than the females they are never reduced so much as to become 

 pygmies. 



In the subfamily Anthosominae the genus Lernanthro'piig is the 

 one in which the male is best known. Here the male is not only 

 smaller than the female, but it lacks the dorsal plates which cover 

 the body of the latter, so that the laminate legs project for their 

 entire length in dorsal as well as in ventral idew. The segments of 

 the thorax are more completely fused than in the female and are 

 seldom indicated by anything except the modified legs. 



In the subfamily Eudactylinae the males of Congericola^ Nemesis^ 

 and Eudactylina are known. They differ from the females in hav- 

 ing a relatively shorter and narrower genital segment, and the seg- 

 mentation in the A^emesis male is almost Avholly obscured. 



In the subfamily Pseudocycninae the males of Pseudocycnus^ the 

 only ones known, differ from the females in the fact that the long 

 genital segment of the latter is replaced by a very short, almost 

 spherical segment, in front of which the fourth legs stand out rigidly 

 on either side. The cephalothorax is relatively the largest region in 

 the body, while the abdomen terminates in two large flaring anal 

 laminae. 



In the subfamily Dichelesthiinae the males of Hatschekia. and 

 Dichelesthiuni are almost perfect counterparts of the females, half a 

 eize smaller. None of the males in any of these subfamilies is found 

 attached to the female after the manner of the pygmy males of the 

 Lernaeopodidae and Sphyriidae. But they are all attached inde- 

 pendently to the host in the same manner as the females. 



