olored as the females, though they have a faint vertical bar on their sides. Individuals lack pelvic fins. Its dorsal fin has twelve rays, while each pectoral fin has seventeen rays. The caudal fin is convex in appearance and has twenty-eight rays, curving outward at the margin. Its lateral series (the number of scales from the back end of the opercle to the beginning of the tail) is twenty-seven scales. The scales are ctenoid, or toothed, on the outer margin. Biology and ecology Larva of the Devils Hole pupfish The Devils Hole pupfish consumes a variety of food items representing nearly all possible food resources in Devils Hole. Its food resources include inorganic particulate matter; the algae Spirogyra and diatoms; the freshwater crustaceans Hyalella azteca and ostracods; protozoa; the beetle Stenelmis calida; the flatworm Girardia dorotocephala; and the freshwater snails Tryonia. The consumption of the various food resources varies seasonally, though in organic particulate matter had a high frequency of occurrence in stomach contents year-round in one study. The inorganic particulate matter consists of primarily travertine, a form of limestone. The three most common food items for each season by frequency of occurrence were: Spring (March through May): inorganic particulate matter (83%), diatoms (75%), and Spirogyra (58%) Summer (June through August): inorganic particulate matter (79%), Spirogyra (46%), and diatoms (46%) Autumn (September through August): inorganic particulate matter (95%), Spirogyra (74%), and Hyalella azteca (33%) Winter (January through February): inorganic particulate ma