Mayfly Genus Pentagenia

Rather large mayflies, wing 14 to 15 mm. in length; a broad dark band dorsally on abdomen. Eyes of male quite large, approximated apically. Posterior margin of head of female almost straight between the eyes. Fore leg of male very short relatively, only slightly longer than head and thorax combined. Fore tibia 114 to 114 times as long as femur; tarsus slightly longer than femur. Basal tarsal joint short; second subequal to fifth; third and fourth progressively shorter. Hind leg very similar to fore leg; distal tarsal joint about as long as the three preceding joints together. Proportions of joints of leg of female much as in hind leg of male. Wings very much asin Hexagenia, except that the cells in the costal angulation of the hind wing may be divided by a cross line into two series. Penes simple, rod-like, divergent apically, united only at base. Subanal plate of female with a V-shaped median notch on apical margin; a short projection at each outer corner, directed outward and backward. Tails three in both sexes, middle one very short.

Wings and genitalia of the imago are figured by Eaton, Needham and Spieth; the two last mentioned also give nymphal structures.

Frontal process on head of nymph bifid. Mandibular tusks relatively stout, crenate on outer (upper) margin. Maxillary palp very stout, 3-jointed; second and third joints fringed with long hairs. Galea-lacinia wide, somewhat conical. Labial palp 2-jointed; distal joint long, clavate, covered densely with long hairs; several long spines near tip (fig. 83).