Inconsistencies in larval habits of the Nearctic Calocalpe population have been known to lepidopterists of eastern North America for over a decade, at least since the publication of The Lepidoptera of Nantucket and Martha's Vineyard Islands, Massachusetts by Dr. Frank Morton Jones and Mr. Charles P. Kimball (Nantucket Maria Mitchell Assoc., IV, 1943). In writing of the occurrence of undulata on Martha's Vineyard, Dr. Jones mentioned “solitary larvae, identified by breedings, occasional on Azalea”. Since only the common gregarious larvae on cherry were known up to that time and always considered as representing an American variant of undulata, the report of a solitary larva on a totally different food plant sounded interesting. This was drawn to my attention by Mr. Laurence R. Rupert of Sardinia, N.Y., who did so much to inspire my interest in Lepidoptera in earlier years. On a collecting trip with him to Martha's Vineyard in 1947, one of the things sought for was the Calocalpe mentioned by Dr. Jones. We did not find any, but since that time Dr. J. McDunnough and I on a number of occasions have bred specimens from solitary larvae on Rhodora at Halifax. Since Rhodora and Azalea are closely related, I assume this to be the same as the Martha's Vineyard species. Dr. McDunnough bred one from a larvae on Spiraea, the specimen emerging just in time to be mentioned in this paper. On another occasion I bred one from a single larva on willow, undoubtedly also the same species, and this provided the first clue to its relationship with the Palaearctic willow-feeding undulata.

Periodic outbreaks of the large aspen tortrix, Choristoneura conflictana (Wlkr.) severely defoliate trembling aspen, Populus tremuloides Michx., in parts of Manitoba and Saskatchewan. The inadequacy of information on the insect prompted further investigation of its life history and the factors affecting its abundance. Field studies were conducted in Northern Manitoba and Saskatchewan, where from 1950 to 1954 the insect was found at various population levels.

The following are descriptions of a new species of the subfamily Typhlocybinae from northern Canada, and one new species of the subfamily Deltocephalinae from Eastern Canada and a second from the Prairie Provinces. The type material is in the Canadian National Collection, Ottawa.

Sweetman (1940) suggested that unfavourable spring weather is probably the most important natural check for the forest tent caterpillar, Malacosonza disstria Hbn. He observed that warm weather in April or early May that induces hatching, followed by a week or more of cool weather, frequently destroys the caterpillars. Blackman (1918), Tomlinson (1938), and Hodson (1941) have reported similar observations.

The classification of species of the Lygus complex has been somewhat unsatisfactory. Many species were assigned to the genus Lygus solely on the basis of superficial characters and many were transferred from one species group to another on the same inadequate basis. In the present paper the characters of the genera and subgenera of the complex are defined.

Study of structures of the internal male and female genitalia revealed characters of considerable taxonomic value. These, taken in conjunction with external taxonomic characters, enable the species of the complex to be classified into 14 genera or subgenera. Among other things, the investigation showed that the economically important “lygus” bugs are not of the genus Lygus Hahn, but of the genus Liocoris Fieber.

Larvae of the larch sawfly, Pristiphora erichsonii (Htg.), feed on the foliage of conifers of the genus Larix. In Manitoba and Saskatchewan, where the studies described here were conducted, the native host is tamarack, L. laricina (Du Roi) K. Koch. At outbreak population levels larval feeding commonly causes complete defoliation. Trees show a marked reduction in foliage production after three or four successire vears af severe defoliation (6). As a consequence, larval starvation is commonly associated with declining host vigour. Starvation reduces the population size directly by causing larval mortality and indirectly by reducing the reproductive capacity of the partially starved survivors. This paper deals primarily with the measurement of the sub-lethal effects of starvation during the last larval stadium as studied in laboratory-reared and field-collected insects.

Many factors influence the host preferences of entomophagous insects and have an important role in determining the fate of parasites in the field. Some of the factors influence the ability of parasites to locate their hosts. Others determine the suitability of the host as a medium for larval development (7, 15, 18, 26, 27, 31). These factors together determine the range of hosts attacked and control the degree to which nonpreferred hosts are selected.

Phytophagous orchard mites have become so troublesome in British Columhia during the last decade that special attention has been given to studies on their ecology and control. An important prerequisite for such studies is an accurate and rapid method of estimating population densities of both the mites and their predators. As some mites are less than a fifth of a millimetre long, it is difficult to determine the numbers of adults present on foliage, quite apart from the eggs and other immature stages.

Methods for estimating orchard mite populations developed to date may be classified as either direct, in which the mites are counted on the leaves or estimated, or indirect, in which the mites are removed from the leaves and a known fraction is counted.

The larch sawfly, Pristiphora erichronii (Htg.), is currently considered a major forest insect pest in Canada. At the present time within Canada, the sawfly reacts to parasitism by Mesoleius tenthredinis Morley in two ways. In Manitoba and Saslratchewan the sawfly encapsulates approximately 100 per cent of the parasite eggs deposited, whereas in British Columbia encapsulation rarely exceeds four per cent (Muldrew, 1953). The reasons for the difference in degree of encapsulation are apparently unknown; however, since the origin of the sawfly itself is obscure, the possibility exists that a native species, an introduced species, Or a combination of both may he present, or that geographical or ecological units may have arisen. Studies now under way by officers of the Forest Biology and Entomology divisions are attacking the problem of identity and origin following the pattern established for the European spruce sawfly, Diprion hercyniae (Htg.). In this instance, as with the larch sawfly, parasites were introduced on the assumption that the pest had been introduced from Europe. Critical investigations by Reeks (1941) and Balch, Reeks, and Smith (1941), involving morphological, cytological, and other biological characters, showed that the species occurring in North America was one of two species common in Europe, and previously referred to there as Gilpinia polytoma (Htg.). Balch et al. (1941) showed that D. hercyniae had been introduced into North America.

The high degree of host specificity of many phytophagous insects is a commonplace, yet remarkable phenomenon. Nevertheless it has been relatively neglected as a field for experimental study.

The first beginning was made about 50 years ago when Grevillius (1905) found that the larvae of the browntail moth Euproctis chrysorrhoea (L.) which feeds on the chick weed, Stellaria, could be induced to feed on other plants by smearing the leaves with a paste containing tannin which is a constituent of chick weed. It is un1ikely that this work was highly critical with respect to the chemical purity of the test preparations, yet the basic principle inherent in all experimentation in this field was employed. That is to say, a relatively isolated chemical constituent of the host plant together with some ingestible substrate other than the host plant tissue was offered to the insects. Obviously, the induction of feeding indicated that the test material contains some substance that stimulates the appetite of the insect.

This study was undertaken as part of a broader investigation of the behaviour of the jack-pine sawfly, Neodiprion americanus banksianae Roh. The greater part of the investigation was directed towards an understanding of larval group-feeding behaviour, but in order to clarify the situation in which this insect begins larval life, large numbers of egg clusters were analysed with special attention paid to the positional relations of egg-bearing needles. Such analysis has permitted certain inferences on the oviposition behaviour of this insect and this indirect information is of value in view of the difficulties experienced in efforts to induce this species to oviposit under laboratory conditions for direct observation. Fortunately, egg clusters obtained from the field are well adapted to descriptive measurement and analysis, for in order to lay its full complement of eggs the adult female sawfly must select as many as 20 to 30 needles, thus leaving behind it a readily measured record of its egg-laying behaviour.

Numerous studies have shown that the cuticle of insects is complex and highly-differentiated and that the complexity varies from species to species (2, 8, 11, 13, 14, 17, 18).

The object of this study is to determine cuticular relationships between the grasshopper, Melanoplus bivittatus, and other insects already studied. This work was carried out by means of chemical tests and permeability measurements on fresh material rather than by methods of fixing and sectioning.

The appearance of an article “Window flight traps for insects” by Chapman and Kinghorn (Can. Ent. 87 (1): 46-47. 1955) suggests that it may be well to describe another flight trap. Specimens taken by it have been labelled “caught in cheesecloth trap”, a statement which is true but perhaps enigmatic.

While on the late Ralph Hopping's staff, the writer built a number of cages for rearing forest insects in southern British Columbia. These cages were all 6 × 6 × 6 ft., each on a cloth covered wooden platform, with a minimum super-structure of 2 × 2 in. lumber to the inside of which cheesecloth was tacked to form an insect-tight enclosure. One entered by a door on the lower part of the north or east side.

During 1954, I had the opportunity of examining a large collection, circa 3,500 of unidentified Corixidae which had been accumulated in the Canadian Department of Agriculture over a period of years. These notes consist of a list of species identified, with observations where pertinent when these records are new state or country records compared with the full lists of localities given in H. B. Hungerford's ‘The Corixidae of the Western Hemisphere’ 1948, Univ. Kansas Sci. Bull. Vol. XXXII, pp. 1-827.

The study of populations and population trends of a forest insect embraces a wide field of activity. By implication, it includes a consideration of all mortality and survival factors. Therefore, in developing this portion of the symposium, it will be necessary to refer briefly to other related topics to be covered later. In addition, to obtain a proper understanding of the subject under discussion, the mode of operation of some population influences that will not be introduced by other members of the symposium will have to be described.

The thrips Frankliniella tritici (Fitch) occurred in great abundance early in May, 1954, in orchards of tree fruits in Essex County, Ontario.

Observations during the first three weeks of May showed that this insect was abundant on the foliage and blossoms of apple, sweet and sour cherries, plum, and peach. Sweet cherry, European plum, and peach suffered the greatest attack. On sweet cherry and plum large numbers of eggs were inserted in blossom stems, styles and apices of the ovaries. From 30 to 50 per cent of the blossoms of sweet cherry and plum were destroyed, apparently because of disruption of tender tissues by the large numbers of eggs inserted in them; a considerable number of the fruits remaining on the trees were injured by feeding of adults and immature stages of the thrips (Fig. 1).

In Western Canada, Aedes flavescens (Müller) is found mainly on the prairie, where it is one of the commonest of the blood-sucking pests of livestock and man. It has also been taken as far north as Churchill, Man., and Alaska (Rempel, 1950). Information on its flight range is useful in planning control programs. Field and laboratory studies on the flight range of this species, with radio-active phosphorous for tagging, were conducted at Saskatoon and Indi, Sask., in 1952. The project area is almost flat in the north and west and rolling in the south and east; the Blackstrap Valley separates the two topographical areas.

The Lygus complex was treated as a number of genera and subgenera in a recent paper (Kelton, 1955). The genus Liocoris Fieber now contains the economically important species, the pratensis group, referred to collectively in the literature as the “lygus” bugs.

In the Prairie Provinces of Canada, several species of the pratensis group are of economic importance mainly in the growing of alfalfa seed, especially in the north-central agricultural region and in the irrigated areas of the southwest. A review of the names used in dealing with these pests on the Canadian prairies showed that most of them were based on misidentifications, although fortunately the use of the names has been fairly consistent. Such widely recorded and used names of Lygus pratensis (L.) and L. elisus Van D. have each been used for specimens of another species, and L. hesperus Kngt. for those of three other species.

During a study of the effects of spray chemicals on the arthropod communities of peach orchards in the Niagara Peninsula, Ontario, begun in 1946, Stethorus punctillum Weise was found to be one of the more important predators of tetranychid mites. An investigation of its biology was undertaken in 1949 and continued through 1952. This paper presents chiefly the life-history, behaviour, and ecological aspects.

Our present day concepts of the classification of insects are the result of a long period of development in the observations and thinking of the early naturalists, zoologists, and in more recent times, the more specialized entomologists. We are now so far removed from the original concepts on which the early classifications were based that many of us fail to realize that the systematic arrangement of animals, and particularly the invertebrates, was long a difficult and complicated problem which gave risk to much confusion. It may, therefore, be profitable as well as interesting to review the development of insect classification with respect to the ideas that have had a profound influence on the subject, and the men who have proposed these ideas and exerted the greatest influence. So, I propose to attempt to examine, evaluate and report to you some of the more important ideas and episodes in the development of this phase of insect taxonomy.