162 JOTJKNAL OF ENTOMOLOGY AND ZOOLOGY 



there are still many otlier places in which some one or another 

 of tliis isopod group dwells. Some are securely fortified within 

 the minute chambers of the sponges; some are tube builders 

 or excavators; some have sought the crevices of the big dry 

 rocks where they neighbor with the shore cral)s; and some 

 are even fond of the muddy shore of a stagnant lagoon; still 

 others inhabit the gill chambers of tish or crabs, living a 

 parasitic and degenerate life. Though many of the Isopoda 

 are marine there are also many terrestrial and fresh-water 

 forms, the former known to most of us by their representative, 

 the common sow-bug, or wood-louse, or pill-bug, as it is vari- 

 ously called. 



Not less interesting than the numbers and habitat of these 

 animals is their diversity in color and form as adapted to their 

 environment. Those inhabiting the sandy and rocky places are 

 provided with a chitinous crusty structure and are colored a 

 dull gray or brown which favors well their characteristic love 

 for obscurity. Those which dwell in the pools or on the moss 

 are more delicate and are provided with special swimming, 

 organs. On the green Algse there are elongated isopods, green 

 in color and hardly distinguishable from the moss on which 

 they occur, and similarly brown forms on the brown Alga\ A 

 most interesting instance of these color adaptations which I 

 observed in my study at Laguna Beach was that of an isopod 

 which dwells on the oral surface of a sea urchin; it was a dark 

 reddish-purple in color, so very like that of its host that one 

 could scarcely distinguish it when at rest. Much might be said 

 of the diversity and beauty of color of the marine Isopoda, 

 but that is a study in itself. 



It appears that the Isopoda and Amphipoda are somewhat 

 closely related, since both can be grouped under the . more 

 limited division, Arthrostraca. The)' differ from each other 

 as follows : the Isojjoda are dorso-\'entrally flattened, the 

 Amphipoda laterally compressed. There are other differences 

 such as modified second and third thoracic appendages and a 

 differentiation of abdominal segments into two sets in the 

 Amphijjoda, A common and ^Jopular distinction is the crawl- 



