290 AQUATIC MICROSCOPY FOR BEGINNERS. 



a male, has a bright yellow tail, the center of the body 

 white, with a blue line near the posterior border, and 

 dark-brown cceca. 



A species of Arrenurus with a hard and reticulated 

 surface is not uncommonly captured among Cerato- 

 phyllum and Myriophyllum in rather shady place's, 

 which, I think, all the water-mites prefer. So sensi- 

 tive is it to the heat and' the direct light that even a 

 moment's exposure to the sunlight out of the water 

 is fatal. 



6. Atax (Fig. 197). 



The anterior coxa are in contact by their entire 

 length, and the posterior extremities of the two anter- 

 ior groups on each side are also often in contact, thus 

 appearing to compress the mouth between them. The 

 posterior coxa are also in contact for their whole 

 length, but they do not touch those of the opposite 

 side of the body, that is, they do not meet in the 

 median line. The fourth coxa, or the one belonging 

 to the most posterior leg, is usually much larger and 

 broader than any of the others. The two ventral 

 plates are narrow and curved, and the tubercles on 

 each of them rounded and translucent. The front 

 pair of legs are long and curved and the hairs on them 

 bristle-like. When the mite walks these legs are held 

 rigidly in front. The color of the body varies, as it 

 does in the other forms. A yellow Atax is not un- 

 common in our ponds and shallow, slowly flowing 

 streams. 



P^ 



Fig, 197.— Coxse of Atax. Fig. 198.— Eyeplate of Limn6chares. 



