This paper has been extracted mainly from the manuscript of a revision of the tortricid subfamily Archipinae, to make available a scientific name for an injurious, undescribed Choristoneura species that feeds in the larval stage upon pines, particularly jack pine, Pinkus banksiana Lamb., and red pine, P. resinosa Ait. This insect and the closely allied Choristorneura fumiferana Clem. are compared under the following topics: taxonomic history, maculation, morphology, and distribution. References are cited only if they contain information of taxonomic significance; the vast amount of economic literature dealing with these species has been omitted. This paper is followed by a comparative study of the larvae of the two species by Miss M. MacKay, by one by Miss C. E. Cox on the mathematical significance of the anatomical differences in the larvae and adults of both species, by a discussion of some of the parasites of the pine species by G. S. Walley, and by a discussion by S. G. Smith of the isolating mechanisms aperating between the two species.

It has long been known that a series of late-instar larvae of Choristoneura fumiferana (Clem.) may be distinguished from one of C. pinus Free. by colour differences of the head and prothoracic shield: specimens of the former usually have dark heads and light prothoracic shields; specimens of the latter usually have light heads and dark prothoracic shields. However, intensive study of the larvae, including numerous specimens of C. fumiferana from the spruce-balsam fir areas of Algonquin Park, Ontario, and of C. pinus from jack-pine areas at Normandale, Ontario, has shown that there are highly significant structural differences in the head; these differences serve to identify small series of either species and most single specimens.

During the course of genetic studies on the spruce and jack pine budworms, it was noted that there are distinct morphological characters on which the pupae and egg clusters may be separated. They are described here as a contribution towards the taxonomic separation of Choristoneura fumiferana (Clem.) and C. pinus Free.

A rapid means of identifying species of insects on the basis of physical measurements is useful to the field worker. The efficiency of the postclypeal index in separating the larvae of two closely allied species is illustrated herein. Occasionally species fall into overlapping subgroups, making it difficult to determine the characteristics of a given subgroup. A method useful in identifying such subgroups is outlined herein.

According to Dobzhansky (1951a, p. 262) “Species are … groups of populations the gene exchange between which is limited or prevented by one, or by a combination of several, reproductive isolating mechanisms”. This definition follows from his concept of a species not as a static unit but as a stage in the process of evolutionary divergence. Limitation or prevention of gene exchange is a property of geographic and reproductive isolation (Mayr, 1912), the various types of which Dobzhansky lists as follows:

I. Geographic or Spatial Isolation

II. Reproductive Isolation

A. Ecological Isolation

B. Seasonal or Temporal Isolation

C. Sexual, Psychological or Ethnological Isolation

D. Mechanical Isolation

E. Gametic Isolation

F. Hybrid Inviability

G. Hybrid Sterility

H. Hybrid Breakdown

The following list of hymenopterous parasites of Choristoneura pinus Free. is based on an analysis of two collections that the writer recently received through the kindness of Dr. T. N. Freeman. The first collection consisted of 116 mature larvae and pupae of C. pinus taken by Dr. Freeman at Normandale (Norfolk Co.), Ont., early in July, 1951, in a plantation of Pinus banksiana Lamb. Rearings from this lot, at Ottawa, by Dr. Freeman and the writer yielded 48 moths and 41 specimens of parasites, the latter comprising 10 species. There was a pupal mortality of 27 specimens. The second collection consisted of 75 adult parasites that were reared at Ottawa by Dr. Freeman from a lot of 456 pupae of C. pinus taken by Mr. V. Hildahl at Beauséjour, Man., during July, 1951, on P. banksiana. There were five species of parasites in this collection, three of which are not represented in the Normandale material.