Mayfly Species Caudatella columbiella

Similar to Caudatella heterocaudata, but different in that Caudatella columbiella has paired medial spines on abdominal tergum 1, the other paired medial spines sharp at the tips, and cerci that are approximately one-sixth the length of the median filament, or about one-half the length of the abdomen.

Similar to Caudatella heterocaudata, but different in that male adults of Caudatella columbiella (forewing length ca. 6 mm) are smaller than those of Caudatella heterocaudata (forewing length at least 7mm), and Caudatella columbiella male adults usually have abdominal maculation that is not as highly contrasted from the base coloration.

Eyes dark reddish brown. Thorax dark olive brown, the pronotum with considerable black shading. Median and lateral sutures of the mesonotum black-marked. A yellowish patch within which is a black line lies anterior to the wing base; the black line continues to the fore coxa. Mesosternum blackish brown with olive brown shading. Legs deep olive; fore femur and tibia tinged with black; fore tarsus about equal in length to the tibia, and both of these joints longer than the femur. Wings hyaline; longitudinal veins somewhat smoky, cross veins pale. Abdominal tergites olive brown; the first four tergites with broad black bands anteriorly, which bands are reduced to semicircular dorsal patches on the posterior tergites. A series of lateral black patches is also present, which tend to fuse with the dorsal bands on the anterior segments. Sternites pale olive; an irregular mid-ventral black band and similar black lateral bands. Forceps smoky, the third joint short. Penes united, forming an upcurved rod. (See fig. 156) Tails smoky, the middle one twice as long as the outer ones.

Nymph with well-developed dorsal abdominal spines; head and thorax smooth; black abdominal markings as in the imago; middle tail much longer than the outer ones.

Head and thorax of nymph smooth. Legs rather short; femora somewhat flattened. Lateral extensions of the abdominal segments practically wanting, the postero-lateral spines not produced. Gills present on tergites 3-7. Dorsal spines prominent, strong; incurved, becoming progressively longer and further apart from tergite 2 to 7, but shorter and closer together on tergites 8-9. General color dark brown, the head blackish; legs without pale bands. Abdominal sternites with a mid-ventral reddish brown streak and on each side a lateral row of brownish dashes. Tails brownish, the joinings darker; middle tail almost three times the length of the outer ones.