the Glll-chamhers of Land-crabs^ 379 



Tlie fact?, with localities, may be sliortlj statdA thus : — 



Gecarcinus quadratus : from Clarion Island (Pacific). 



One specimen only examined. Very many small 

 Oligochaita found on and among the gills. 



Cardiscma hrtipes : (a) from the Admiralty Islands (' Chal- 

 lenger ' Collection). 



Two out of three specimens examined had dipterous 

 larvse in their gill-chambers. 



[h) from Christmas Island. 



One out of three specimens had a fragment of a 

 larva adhering to tlie outside of it, near the lateral 

 opening of the gill-chamber. 



Gecarcoidea lalaudii: from Christmas Island. 



Out of three specimens one provided three very 

 small larvae. 



Mr. F. W. Edwards, of the Entomological Department of 

 the British Museum, who has examined the dipterous larva?, 

 kindly supplies me with the following information : — 



" Dipterous larvse from Cardisoma hirtipes. — These larvae 

 are evidently Syrphidffi, and apparently belong to the sub- 

 family Eristalinai ; they differ from Eristalis in the more 

 elongated form and the lack of any obvious separation into 

 'body' and 'tail.' 



" Larvffi from Gecarcoidea lalandii. — These are also 

 Syrphidae, but in the present state of our knowledge it is 

 impossible to assign them definitely to any subfamily. They 

 appear to lack the extensile ' tail ' of Eristalisy 



Whether these larvse ought properly to be considered 

 parasites of the crabs is, perhaps, a matter of doubt *. It is, 

 of course, possible that they arrived in their gill-chambers 

 accidentally. They may have wandered there from some 

 decaying matter upon which the crabs were feeding, according 

 to their habit, or from the water of some stream entered by 

 the crabs. According to Dr. C. W. Andrews [i], Cardisoma 

 hirtipes (referred to under the name of C. carnifex) is never 

 found lar from the streams in Christmas Island, and lives in 

 burrows in the mud of the banks, and it would be rash to 



* It should be borue in mind that there is a remote possibility that the 

 eggs were deposited upon the crabs after death, in which case the larvae 

 could not be called parasites. 



