NO. 1350. NATURAL HISTORY OF THE ISOPODA—RTCRARDSOX. 25 



destructive lial)it. Sjjhieroma vasfafor S. Bate conies from the Indian 

 Peninsula, where it was procured "from a piece of wood wliicli had 

 formed part of a railway bridge over one of the backwaters of the 

 west coast." The wood is described as being " lione3''combed with 

 cylindrical holes, in many of which the animal Avas rolled up like a 

 l)all." Sj}/i;er()t/i(( (lextructor Richardson was found boi'ing the ])i(M's 

 on St. Johns River, at Palatka, Florida. Sections of the wood siiowcd 

 that the diameter had been reduced during a period of eight years 

 from 16 inches to 7^ inches. The whole surface of the wood was 

 bored with holes averaging in size about 5 nun. in diameter, and in an 

 end section the holes were arranged in concentric rings between the 

 rings of animal growth, showing flie little animals' preference for the 

 soft pine. Very strong mandibles, projecting be3^ond the labrum 

 most conspicuously, provide a perfect eqidpment for this destructive 

 work. 



In decided contrast to the above-mentioned habits, Hallez has 

 recenth^ pointed out some of the beneficial work of these little crea- 

 tures. He has found that Enrydtce jxdeJtra Leach is the principal 

 agent in maintaining the healthfulness of the coast at Portal, France. 

 Shark fishing is an important industry of the people of Portal, who 

 consume a great many of these fish and export a large number of them 

 to Paris. The heads of the fish are thrown on the beach, but they are 

 instantly surrounded l)v the little Crustacea which leave only the car- 

 tilaginous skeleton. 



Hallez believes that each locality has a species especialh' adapted to 

 the conditions of the place for carrying on this sanitary work along 

 the coast. 



9. MOPE OF LIFE. 



Many of the Isopods are ectoparasites. The Cymothoidre and ^Fgidre 

 are found attached to the fins and gills and in the mouths of fishes. 

 Some of the Cirolanida? are also parasitic on fish. Dr. Goode said 

 of OJenclva prdRgustator that these forms are not parasites in the true 

 sense of the word, drawing nourishment from the fish to which they 

 attach themselves; they are commensal rather, stealing shelter and 

 transportation, but not subsistence. When the fish to which they are 

 attached die, they change their quarters and seek a new ho.st. OJcn- 

 cira prH'yiistdtor (Latrobe) is a very abundant parasite, infesting a 

 large per cent of the menhaden from tiie Potomac. 



^(/(itJina l<>li(jinea Harger was olitained from the mouth of a s<[uid. 

 Other specimens, however, have been found parasitic on 3'oung mul- 

 let, showing that the species is not parasitic solelv on the squid. 



Parasitism is the mode of life chiefly with th(> Epicaridea. The 

 famil}' liopyridie inf(\st the shrimps and crabs, aiul \w\^ found either 

 attached to the abdomen of the host or witiiin th(> branchial cavit}", 

 beneath the carapace. A crab or shrimp thus infested is rcvidily 



