SEGMENTED SCHIZOCOELS 



239 



Figure 14.13 Class Crustacea. Subclass Malacostraca. Order Nebolioceoe: 1, Epinefao/io, a primi- 

 tive shrimp ( x 5), marine. Order Mysidacea: 2, Myiis, an opossum shrimp (x 10), marine; note the 

 brood pouch under the thorax. Order Cumacea: 3, Diastytis ( x 5), marine. Order Tanaidacea, 4, 

 Tanais (x 5), marine; note the incubation pouch at the base of the fifth leg. Order Isopoda: 5, Asellus, 

 a fresh-water sowbug (x 2); 6, Oniscus, o sowbug{x 2), terrestrial; 7, Armodi//ium, o pillbug (x 2), 

 terrestrial; note the resemblance to a sowbug; 8, Idolheo, a kelp sowbug (x 1), marine. Order 

 Amphipodo: 9, Gommaros, a scud (x 2), fresh water; 10, Caprello (x 2), marine. Order Stomatop- 

 odo; 1 1, Squilla, a mantis shrimp (x 2), marine. 



ORDER ISOPODA (Isopods) 



Diagnosis: no carapace; body usually dorsoven- 

 trally flattened; at least last six pair of thoracic legs 

 very much alike, at least first pair often modified and 

 involved with mandibles; abdomen short, partly to 

 completely fused; marine, fresh-water, terrestrial, 

 many fish and crustacean parasites; all might be 

 called sowbugs, but variously named pill bugs, wood 

 lice, etc. (Figure 14.13). 



The isopods are another structurally variable 

 group. The free-living species are mostly scavengers 

 that eat dead and injured animals and green and 



decaying plants. The common garden sowbugs can 

 cause considerable damage to cultivated plants. 

 Some can roll up into a ball and are called pill bugs. 



Again, the parasitic species are difficult to recog- 

 nize as Arthropoda. The parasites range from those 

 that are of typical isopod appearance to those that 

 are little more than a sac of eggs. 



ORDER AMPHIPODA (Scuds) 



Diagnosis: no carapace; body usually laterally 

 compressed; last six pairs of thoracic legs not of the 



