FIELD BOOK OF PONDS AND STREAMS 



Hyallela. — This is a very common amphipod in the ponds 

 of all the eastern states (Fig. 129). In early spring it gathers 

 in mats of the alga, Spirogyra, with another amphipod, 

 Gammarus (Fig. 130), feeding on the dead filaments. Embody 



Fig. 129. — Amphipod, Hyallela, widely distribut- 

 ed through the eastern states: i and 2, grasping 

 legs; 3, walking legs; 4, swimming legs; 5, jumping 

 legs. 



has seen them eating freshly killed snails, tadpoles, and 

 crushed amphipods of tfeeir own species; and he once found 

 a dead water-bird, the sora rail, "alive with Hyallelas which 

 were feeding upon the decomposed flesh." 



Hyallelas live well m aquaria so long as they are sup- 

 plied with living plants — Elodea, Nitella, or Myriophyllum — 

 and a few dead leaves. There, their mating and feeding 

 habits can be watched very easily. In mating the male clasps 

 the female with his gnathopods or grasping legs and swims 

 about holding her beneath him for a period of several days 

 until the female escapes by shedding her old shell, but she is 

 usually captured again after a brief freedom. Hyallelas molt 

 so slowly that the process can be easily observed especially 

 through a hand-lens or reading glass. Females maj^ carry 

 their previous brood of young in their thoracic brood pouches 

 even during the mating swim. One pair of Hyallela knicker- 

 bocheri has been known to produce a clutch of about a dozen 

 and a half eggs 15 times in 152 days. 



Length of adult about one half inch. 



170 



