320 ENTOMOLOGY FOR MEDICAL OFFICERS 



as in the sea, and are eaten in all parts of the world. Many 

 of them are scavengers, and though it would be quite 

 unreasonable to condemn salt-water species on this account, 

 the case is altogether different with those that are taken in 

 fresh water, especially in stagnant water in the tropics, which 

 is liable to dangerous and disgusting contamination. 



The Anomura (ai/oMo?= irregular, and ouyoa = tail) include 

 the Hermit-crabs, Rock-hermits, Mole-crabs, and others. 

 In these the body is either less elongate, or may even 

 be squat ; the abdomen is less massive, and the tail-fan 

 is reduced, hardly ever forming a large fin. The abdomen 

 either is soft and spirally coiled, or, if well calcified, is more 

 or less bent or rolled under the cephalothorax. Even in the 

 most lobster-like of them the abdomen is flexed, and even in 

 the most crab-like of them there is either a tail-fan or some 

 asymmetry of the abdomen ; while the typical hermit-crabs 

 use a cast-off shell as a protection for their soft abdomen. 

 Among the Anomura there is one family — the Ccenobitidce — 

 of dwellers on land, and these are industrious scavengers, 

 especially on the islands and seaboards of the Indo-Pacific. 

 One of the Coenobitidm — the Robber-crab (Birgus latrd) of 

 the Indo-Pacific — attains an enormous size and a weight of 

 at least 6 lb. ; it is eaten, and is spoken of in the account of 

 Drake's famous voyage of circumnavigation as "good and 

 restorative meat," being an eater of fruit rather than a 

 scavenger. 



The Brachyura (/Syoaxy? = short, and oi;/3d = tail) are 

 well known as crabs. Here the body is rarely elongate, and 

 the abdomen, which is often ill developed, is permanently 

 bent under and more or less concealed by the thorax, and 

 never ends in a tail-fan. The abdominal appendages are 

 reduced, in the males to two pairs, which are modified for 

 sexual purposes, and in the females to four pairs, which are 

 used for the attachment of the eggs. Most of the crabs are 

 marine and littoral, but some of them inhabit brackish water, 

 not a few are amphibious and burrowing ; there is one large 

 family that is restricted to fresh water (ponds and streams), 

 and a certain number live on land. The fresh-water and 

 land crabs can be recognised by their broad carapace. All 

 crabs are scavengers, and for this reason the fresh-water 



