The Canadian species of Meloidæ are few in number, but offer considerable difficulty to the student, chiefly from the fact that some of them are extremely variable in colour and size, while in the genus Meloe we meet with a group in which the specific characters have never been accurately determined. The family is characterized by the vesicant or blistering properties of its members (the “Spanish fly” being perhaps the best known in this connection), and, under the name of cantharides, blister-beetles are to be found in every drug store. To the agriculturist they are often a pest, Macrobasis unicolor often doing considerable damage to potatoes. The naturalist finds in the curious modifications of the antennæ of the males, a theme worthy of his careful study.