176 SPOLIA ZEYLANICA. 
small circular patches of black arranged along the back 
where the layer of sand was interrupted and the black integu- 
ment showed through. It is possible that there may be 
groups cf sensory cells at these places. 
Although Halodeima atra is one of the most abundant, and 
at the same time one of the largest Holothurians found on the 
Ceylon coast, it is not used commercially as “ béche-de-mer ” 
or ‘‘ trepang.” This is also the case with Bohadschia mar- 
morata, a large species which is so abundant at Trincomalee. 
So far as I know the béche-de-mer which is most commonly 
dried and cured by the Jaffna fishermen for export is 
Thymiosicya scabra (Holothuria scabra). 
Colombo, July 16, 1915. JOSEPH PEARSON. 

Cannibalism in Pulchriphyllium crurifolium, Serv.—Mr. E. E. 
Green states in Spolia Zeylanica, Vol.II1., p. 221, that specimens 
of Pulchriphyllium crurifolium, Serv., in captivity frequently 
nibble away portions of their companions. When Professor 
Plate was in Ceylon, he stated in the course of a lecture delivered 
before the Ceylon Natural History Society that Green was 
mistaken in supposing that the insects nibble each other. He 
remarked that the erosion of the sides of the body and tegmina, 
which Green put down to nibbling, was really part of the mimetic 
character of the insects, and was not an artificial effect, but 
the result of the infinite capacity for variation which this 
insect posesses, and which is shown in the colour-markings. 
From personal observation I am able to refute this latter 
view of the case, as I have repeatedly witnessed the insects 
nibbling each other. It is amusing to watch the frantic 
efforts of a leaf-insect to dislodge its assailant when it is 
attacked. The adult insects seem to let each other alone, 
but half grown or very young ones are constantly to be seen 
chewing calmly, while their victims writhe and struggle to 
free themselves. This habit seems to be induced by over- 
crowding or shortage of food, and many vegetarian caterpillars 
become cannibals under the same circumstances. 
Colombo, June, 1915. G. M. HENRY. 
