The species averages larger than either brevis or abbreviatus and may be separated from the former readily by its green face, by the striking differences in the vulvar lamina and by the hamules and male appendages. In brevis the tooth on the appendage is nearer the end and the space from it to appex is noticeably curved while in viridifrons this space is practically straight.
It has more points in common with abbreviatus, but in that species the vulvar scale is short and triangular, the hamules are smaller and shorter, and the tooth on the superior appendage of the male is much farther from the apex.
Through the kindness of Dr. Calvert and Mr. Williamson I have at my disposal, specimens from which many of the accompanying drawings were made. In viridifrons, brevis and abbreviatus I have made drawings from different specimens of the same species to show slight variations.
This is Gomphus sp. Williamson, Dragonflies of Indiana, 294.
A COMPARATIVE STUDY OF
GOMPHUS FURCIFER AND VILLOSIPES.
James S. Hine.
It seems that nearly every author who has considered these two species has compared them. Considering general appearances they are much alike but can be separated easily by several details and as I have good material of both sexes of the two species before me, I thought it might be of consequence to consider in a comparative way some of their characteristics.
The occiput in both sexes of villosipes bears a prominent tooth at the middle of its upper edge. This tooth varies some in different specimens, it ends above in a single point or it may be widened and end above in three or more points. In furcifer there is no tooth on the occiput in either sex.
The vulvar scales are very different, in villosipes the part may be said to be triangular with the free sides curved and the apical part divided for about half the length of the scale. In furcifer its basal part is similar but the apical part is produced, giving quite a different form. In the former species the scale is about one-third as long as the ninth segment, while in the latter it is about three-eighths as long as that segment.
The abdominal appendages of the male are different. From dorsal view those of furcifer are rectangular with the inner distal angle very much produced inward and backward; in villosipes they are wide at base, oblong, with the outer distal part broadly rounded and the corresponding inner part produced directly backward. The hamules are characteristic and may be explained best by reference to the figures.