Herriott. — Occurrence and Habits of Lepidurus viridis. 287 



window-light. A small quantity of mud from an aquarium- jar was also 

 added, as no direct information concerning the proper food could be found. 

 On the mornings of the 25th and 26th four cast exoskeletons were found 

 in the water, only one of them, however, being perfect. All these animals 

 lived for over a week, then began to die off, and were removed as soon as 

 they were noticed to be dead. The last one died on the 13th October, having 

 lived in the laboratory just three weeks. 



On the 14th October another larger supply of Lepidurus viridis was 

 brought in from Springston, and all were put together into a large enamel 

 bowl with plenty of mud. These specimens were much smaller than those 

 of the last collection, and varied considerablv in size and colour. The number 

 was roughly estimated to be about thiity-five. On the 18th nine specimens 

 were put in another smaller bowl in clear water. On the following day 

 one animal (A) was noticed to be dead, and on closer observation one side 

 of its carapace was seen to be very irregular in outline. Another animal (B) 

 was apparently dying, lying on its back and moving its legs very feebly. 

 Two hours later another animal was noticed in close proximity to A, and 

 when it moved away more than an hour later the other side of the carapace 

 of A was quite broken and irregular. Before long A was visited by two 

 others, and by that time more than half of it had disappeared. The sus- 

 picion aroused by the great decrease in numbers since the collection had 

 been brought in was now confirmed. There could be no doubt that the 

 animals, deprived of their natural food, were eating the bodies of their 

 fellows. As this promised to be interesting, four others were taken from 

 the large bowl, in which the water was too muddy for observation, and 

 placed in a third bowl of clear water. 



The numbers were carefully counted next day. with ■ the following 

 results : The original bowl (I) now contained seven animals ; in the second 

 bowl (II) only seven out of the nine put in two days before were alive, 

 nothing was left of A, and only part of the head of B ; in bowl III there 

 were still four, but one of them was lying on its back, moving its legs very 

 feebly, most active whenever any other animal came near it, as though 

 conscious of its danger. This made a total of eighteen left out of the 

 original thirty-five after six days. There could be no doubt about Lepi- 

 durus being carnivorous. On each of the following days the numbers were 

 counted and were found to be less and less, till on the 27th there were three 

 left, one in each bowl. Of the four originally put into bowl III the smallest 

 was left, a dark-green animal. In the other two bowls the largest were left, 

 and both- were mottled green. On the 28th the one in bowl III died ; on 

 the 30th that in bowl II was found to be dead ; the last one, in the original 

 bowl (I), died on the 3rd November, having lived in the laboratory three 

 weeks. 



These animals had, of course, been living under unnatural conditions, 

 and this may have induced this method of preying on one another. Refer- 

 ences to their natural food are very scanty, there being, in fact, no references 

 to Lepidurus itself, but in describing Apus lucasanus, a species of the allied 

 genus, Packard says (1882, p. 324), " The food of this species appears to be 

 Crustacea, as in dissecting the mouth-parts of one of this species the legs of 

 an Asellus-like crustacean were found partly swallowed. Hence they are 

 quite predaceous in their habits." Weldon (1909, p. 19) describes the food 

 of the Branchiopoda as consisting of " suspended organic mud, together with 

 Diatoms and other Algae and Infusoria ; the larger kinds, however, are 

 capable of gnawing objects of considerable size, Apvs being said to nibble 



