1915.] Fiinna of tJie CJiilka Lake : Crustacea Dccapoda. 2ig 



Ocypoda macrocera, H. Milne-Edwards. 



igoo. Ocypoda macrocera, Alcock, Jonrn. Asial. Soc. Bengal, LXIX, p. 347. 



The colouration of adults of this species is very striking. The carapace is of a 

 faint reddish-chestnut colour, grej^er in patches and towards the margins, and the 

 cardiac region is defined anteriorly by a semicircular red-brown line. The outer 

 maxillipedes and adjacent portions of the carapace are stained with deep crimson, 

 the sternum being tinged with crimson, dull purple, reddish- yellow and white. The 

 chelipedes are red at the base with red spines and the outer surface of the large claw- 

 is bright orange yellow, paler distally. The walking legs are french grey, reddish 

 beneath, with the tips of the claws yellowish. The eyes are greyish- white, with the 

 ocular horn a deep crim.son. In immature specimens, about 20 mm. in breadth, 

 there is no trace of red colouration, the carapace being of a dull creamish tint, 

 heavily marbled with dark grey. 



For the following intetesting notes on the habits of 0. macrocera in its early 

 stages I am indebted to Dr. Annandale : — 



" The 3'oung of this species, both in a late megalopa stage and with their skins 

 still soft after the final metamorphosis, were common on the sandy beach of the 

 Ennur backwater, near Madras, in January 1915 They lay in short and imper- 

 fectly formed burrows under logs (catamarans), drawn up just above the water-line 

 where the sand was still damp. The megalopae were sluggish and somewhat helpless, 

 but could run along the sand with fair rapidity, their abdomens tucked away 

 beneath the carapace like those of adult crabs. They were easily knocked over, not 

 being at all well-balanced and, when handled or molested in any way, lay still with 

 their legs and tail all pressed together and "shammed dead." Their excavating 

 powers were limited. When one was placed in a dish of wet sand , it turned round and 

 round like a dog, moving its limbs in an unco-ordinated manner, until it had found 

 a small hole in which it remained quiescent. The megalopae were not seen coming 

 out of the water, but there is little doubt that they did so at night, for all those 

 found on the shore were approximately^ the same size (almost the same as that of the 

 full}' formed young crabs) , and older members of the same species were observed on 

 several occasions, in the early morning, running towards their burrows with young 

 megalopae in their claws. The larvae exhibited considerable power of colour-change, 

 becoming much paler than u.sual when submitted to a strong light. Their dorsal 

 surface, when they were in their holes, was of an almost uniform dark leaden grey; 

 when they were placed in a glass vessel it became of a pale glaucous shade.' ' 



"The period of the metamorphosis was evidently one of great danger and 

 numerous individuals were observed that had died, both before and after the ecdysis, 

 without apparent injury, probably owing to exhaustion. Allusion has already been 

 made to the cannibal habits of the older crabs of the species, which evidently cap- 

 ture the megalopae and carry them away to be leisurely devoured in their burrows. 

 That they were not merely carrying their young relatives to a place of safety was 

 proved by the fact that one crab was captured carrying the already half-devoured 

 corpse of a megalopa, although in other cases the captives were still uninjured." 



