Williamson (1802) described the white fly Ephoron leukon. From his description of the insect and its habits, recent workers have been able to identify the species correctly. Hagen (1863) suggested that Baetis alba Say is a synonym of E. leukon Williamson. Eaton (1871, p. 124) was undecided as to the identity of E. leukon. In 1883 (p. 47), however, he indicated that leukon is a synonym of albus Say, which he considered to be a member of the genus Polymitarcys. This genus he had erected in 1868, employing Ephemera virgo Oliver as the genotype.

Male. Length 6.5 mm.; of wing 4.8 mm. Face narrow immediately below antennae, thickly covered with bright golden pollen; proboscis black; palpi dark brown bearing fine black hair and lightly dusted with yellowish pollen; antennae yellow; first joint large with a black stripe along upper outer edge and covered with short, stiff black hairs, second joint small, yellow, third joint small, decumbent, black on apical half; arista black, about one and one-half times length of face, lamella (fig. 4) at tip with an elliptical white spot on upper side near base; front black with bluish reflections, especially along the orbits; ocellar bristles black, hair near proboscis whitish.

The following key and descriptive notes have been prepared in an endeavor to lessen the difficulties involved in the identification of the various species of Ptinid beetles that occur, usually as pests of stored products, in dwellings and warehouses in Canada. For a number of years, Mr. H. E. Gray of the Division of Entomology has been collecting these beetles from flour sheds and other types of warehouses throughout Canada. Most of the material on which the key is based was supplied by Mr. Gray, and much of the data on the distribution of several of the species is a result of Mr. Gray's observations.

The North American species were discussed by Fall (1923), under the name Agaporus Zimmermann (1919: 192) . However, as has been pointed out by Giugnot and F. Balfour-Browne, Agaporus, with Hydroporus oblongus Stephens as its type, is a synonym of Laccornis Des Gozis (1914: 111). Des Gozis proposed Laccornis as a subgenus of Hydroporus, with H. oblongus as the type and only species mentioned.