Two species of fire-flies are abundant in western Massachusetts in the early summer and often their display of light presents a magnificent spectacle. Theses species are Photinus scintillans, Say, and Photuris Pennsylvanica, De Geer. Photinus scintillans becomes active very early in the evening, and long before twilight begins its orange-coloured light may be seen flashing among the shrubbery. It is only active during the twilight hour and some time before total darkness has set in its lights have disappeared.

Genitalia: female, ultimate ventral segment nearly four times wider than long, posterior margin slightly emarginate with a short broad medium tooth; male valve broad, short; plates broad at base, concavely, attenuately pointed, two and one-half times longer than valve, equalling the pygofers, which are thickly beset with stout hairs.

Described from two females and two males from Holly., Colo. The small size and the black spot near the anal angle of the elytra at once distinguish this species.

Dr. Andrew Balfour, Director of the Wellcome Bureau of Scientific Research, has submitted to the writer for study part of the Diptera collected on his recent voyage in the American tropics. A species of Simulium from the valley of the Atrato River in Colombia proves to be new and is described below. Through the good offices of Dr. Balfour further interesting material was received from K. S. Wise, Surgeon-General for British Guiana, and from F. W. Urich, Entomologist of Trinidad. These lots contained an additional new species of Simulium each, of which the descriptions follow. Diptera belonging to other groups and of economic interest will be treated in subsequent papers.