PROCEEDINGS OF THE THIRD ENTOMOLOGICAL MEETING 689 



or three are cut it is not noticed, but when they are put singly the 

 damage is more noticeable. The cultivators therefore do not like this 

 mode of cultivation. The only enemy we have in Madras is Ardeola 

 grayi. By draining off the water we noticed some reduction in the 

 number of the young crabs which went to lower fields with the water. 



33.— NOTES ON SOME LAND AND MARINE CRABS AND FIELD- 

 SNAILS WHICH ARE PESTS IN BURMA. 



By K. D. Shroff, B.A., Entomological Assistant, Burma. 



Land Crabs. 

 The specimens of land-crabs collected from the paddy fields in 

 different districts were identified by Mr. Kemp, Superintendent of the 

 Zoological Survey of India, as the following : — 

 (a) Potamo7i dayanum, Wood-Mason, 

 (h) Potamon calvum, Alcock. 



(c) Potamon andersonianum var rangoonense, Roth. 



(d) Potamon pealianum, Wood-Mason. 



Of these, Potamon dayanum is the most common species. The 

 last two species were received from the Southern Shan States. 



Experiment with mahaga on Land-crabs. 



MaJiaga {Linostoma decandrum, Wall.) is a creeper which grows 

 on and at the foot of the Kachin hills. The roots of this creeper are used 

 for poisoning fish. They are pounded and mixed with mud and water 

 and allowed to stand for four or five days. The mixture, which becomes 

 most offensive in odour, is baled into the water and all fishes and insects 

 living therein are killed. 



Eight plots, each eight feet square, were prepared wdth raised bunds 

 and in each plot ten crabs were put after the seedhngs were transplanted. 

 Then the mahaga-wsiteT was poured into these plots. The crabs managed 

 to escape during the night. The plants ought to have been killed by 

 the poison, but they were not, and it is presumed that the maJiaga- 

 powder, which was two years old, had probably lost its property. 



Marme crabs. 

 The paddy fields of Burma, which are completely flooded in the 

 rains and then communicate with permanent sheets of water like rivers, 

 creeks and the sea, are affected by the inroads of multitudes of certain 

 species of marine crabs and field-snails. The following species are 

 found along the seacoast and the margins of rivers and tidal creeks 



s 2 



