The present paper is concerned solely with methods of studying the chromosomes, their number, morphology, and behaviour, in insects. Much has already been written on general cytological techniques used in the study of animals and plants (1, 2, 3 and 4) but no special treatment regarding insects has as yet appeared. The techniques outlined in many standard text books are largely obsolete, and reprints of current improvements are frequently not available in the specialised entomological library. Therefore a review of the procedures commonly followed may not be out of place as a guide to the non-specialist.

In his recent Revision of the Oecophoridae (1941, Proc. U. S. N. M. Vol. 90, No. 3107) Gates Clarke (p. 196) records the larva of Depressaria betulella Bsk. as feeding on both Betula and Ostrya. As material bred by us from Ostrya this past summer in the Ottawa region did not at all match with our series of the birch-feeder I have made a genitalic study of the species of this group in the Canadian National Collection in order to check up on the matter.

Plebeius scudderi empetri Frmn. was described from material taken in early July, 1936, in an Empetrum bog not far from the town of Baddeck on Cape Breton Island. Later in July of that year several similar bogs were observed in various parts of Nova Scotia, but with the exception of a single worn specimen captured in the Cape Canso region, no specimens of empteri were observed. This was thought to be due to the lateness of the season.