Production of webbing, greater fecundity, faster rate of development, and greater ability to thrive on foliage injured by feeding enabled populations of T. telarius to suppress those of P. ulmi on peach foliage in a greenhouse and insectary. However, these inhibitory factors were non-operative in an orchard environment in southwestern Ontario.

The tendency of the two species to populate different levels of a host plant, and of P. ulmi to utilize the upper surfaces of leaves more than T. telarius, each decreased the intensity of competition. The suppression of P. ulmi in an insectary or greenhouse was delayed but not prevented by the above factors.

The habits and dispersal of the pteromalid parasite Nasonia vitripennis and its housefly host, Musca domestica, and their density relationships were investigated. Male parasite longevity averaged 1.62 days and female longevity 6.96 days. The average number of progeny per female parasite was 139.8. When 25 pairs of parasites were placed with 300 housefly pupae of three sizes, the percentage parasitism was 45.0 for the small (less than 2.0 mm. in diameter), 72.8 for the medium (from 2.0 to 2.5 mm.), and 65.7 for the large (greater than 2.5 mm.). The number of parasites produced per parasitized pupa was 2.20 for the small, 4.30 for the medium, and 6.11 for the large pupae. Increasing the extent of superparasitism produced significantly smaller parasite progeny. A significantly greater normal mortality occurred in small housefly pupae (21.5 per cent) compared with either the medium (6.3 per cent) or the large (5.2 per cent).

The parasite dispersed significantly faster when unfed than when fed. Housefly pupae which had been previously exposed to parasites also stimulated the tendency for subsequent parasite emigration. Housefly dispersal was found to be density-dependent under the experimental conditions of the multi-cell population cage.

With an increasing parasite-host ratio the rate of parasitization increased until all hosts at a 1 to 1 ratio were parasitized in 24 hours; percentage of parastized hosts producing parasites reached a peak of 71 per cent at the 1 to 2 ratio; and above the 10 to 1 ratio all parasite progeny died due to super-parasitism.

Several criteria for determining the sex of the southern pine beetle, Dendroctonus frontalis Zimm., were investigated. The combination of the prominence of the frontal tubercles and depth of frontal groove was 100% accurate and was chosen as the best criterion. Data on sex ratios at different points in the beetle's life history are given.

In southern Alberta the fundatrix of P. betae hatches from the overwintered egg in late April and early May and feeds on an emerging leaf of P. angustifolia or P. balsamifera, forming a gall. In the gall it produces alate fundatrigeniae, which migrate from the poplars to beets and produce apterous alienicolae. This form of the aphid reduces both yield and sugar content of beet roots. During the summer several generations of alienicolae are produced. In the fall most of the alienicolae produce sexuparae. These migrate from beets to poplars, where they produce males and oviparae. Each fertilized ovipara lays a single egg on the bark of a poplar tree. The species may overwinter as eggs on the poplars or as alienicolae in the soil. The egg has an obligatory diapause that is terminated by exposure to low temperature. The fungatrigeniae migrate from late June to mid-August and the sexuparae from early September to late October. The potential reproductive capacities of the fundatrix, fundatrigenia, sexupara, and ovipara averaged 163, 13, 6, and 1, respectively. Under greenhouse conditions 20 aphids (alienicolae) produced 9,000 in 6 weeks when the soil temperature was maintained at 27 °C. Below 15 °C. the rate of reproduction was low and death was caused by exposure to 30 °C. for 6 weeks. The most important predators of P. betae were the anthocorid A. antevolens, the flies S. bigelowi, L. pemphigae and T. glabra, and a coccinellid Scymnus sp.

Northern and southern specimens of the fall webworm in eastern North America exhibit color differences in both the adult and larval stages, and have often been referred to Hyphantria textor Harris and H. cunea Drury, respectively. However, they will readily inter-breed and produce viable offspring; differences in wing maculation are not discrete and genitalic differences have not been found; differences in the degree of larval pigmentation are not discrete and depend largely on environmental factors; and the nesting and feeding behaviors are similar. It is therefore concluded that the common webworm (larvae with the head and dorsal tubercles black) in both north and south should be referred to H. cunea, which has priority. A sibling species or race (lighter heads and tubercles and different nesting and feeding habits) occurs sympatrically with cunea in the south and also, rarely, in the north; if it has specific status it cannot be referred to either cunea or textor; so textor is relegated to synonymy.

The population dynamics of the gypsy moth, Porthetria dispar (L.), are being studied on 10 sites in the Town of Glenville, New York. This paper discusses the role of disease and a condition here termed “desiccation” in the dynamics of these populations during a 4-year period, 1958-1961 inclusive.

The term “desiccation” refers to dead pre-pupae that appeared shriveled, and were stiff to the touch, and which had a solid mass of food in their gut. The incidence of desiccation among pre-pupae was closely related to the number of eggs per egg mass produced at the end of the generation (a measure of relative insect density).

Disease incidence among larval gypsy moth populations was directly related to insect density. Disease incidence was also related to site conditions, with higher mortality occurring in wet sites.

When larval populations reached high densities, they always declined from the dense level within a few generations. These declines ranged from a sudden drastic reduction to a much more gradual decline. The former was preceded by virtual food exhaustion, while the latter was not usually preceded by exhaustion of the food supply.

Disease and desiccation were primary factors in producing the sudden type of population reduction noted above. Pathogens may also play an important part in the more gradual type of decline, but this point remains to be clarified.

With winged and wingless males being currently found in Southern Quebec, the pea aphid, Acyrthosiphon pisum (Harris), cannot be regarded as a subspecies of the European species, on the basis of males being supposedly winged in North America and East Africa and wingless in Europe and Asia. The host relationships are apparently different as is also the occurrence in Europe of red forms of the aphid.

The two species described here were discovered during studies on a revision of the Ips of North America. They belong to a group of closely related species composed of Ips tridens (Mann.), I. engelmanni Sw., I. yoboensis Sw., I. pilifrons Sw. and I. sulcifrons Wood. The females in this group have the lower part of the front of the head slightly elevated as in I. yohoensis to very strongly protuberant as in I. tridens. All of them breed in species of spruce. The males of this group are difficult to determine from external characters alone. Descriptions were made under a magnification of 50X, using 100X occasionally.

From May 8 to September 29, 1961 4 species of Corixidae, 5 o f Notonectidae, 1 of Belostomatidae and 1 of Nepidae were collected and the seasonal distribution of each species was noted.

In Gatineau Park near Ottawa Simulium venustum adults were present in appreciable numbers around man (usually 20-100 flies/man/hr.) only between mid-May and mid-June in 1958-60, numbers after late June being negligible apparently because a succeeding generation failed to mature in significant quantity. It is suggested that differences in the duration of the S. venustum biting problem in different parts of eastern Canada largely depend on whether or not streams remain suitable for the aquatic stages after the spring generation derived from overwintered eggs has emerged.

In sweep-net catches of flies attracted to man at fixed sites the proportion of parous flies was nil in mid-May and increased to near 100 per cent by mid-June, 3 change sometimes interrupted by the appearance of a second wave of nulliparous individuals from late fly-producing streams. The latter were anatomically indistinguishable from flies produced earlier apart from reduced body size. The results suggest that the populations studied were anautogenous and that there was no deviation from this condition that could be attributed to variations in the food available for larvae in different streams or at different times.

The proportion of attracted parous flies containing relict eggs sometimes tended to increase towards the end of the season, suggesting that a large proportion of the few flies still remaining had completed two or more ovarian cycles.

Parous flies tended to be particularly active in late afternoon and evening but instances when this diurnal pattern did not occur were observed.

The recent black-headed budworm outbreak on the Queen Charlotte Islands is the fourth recorded association between budworm trends and weather. The decrease in this instance was associated with a prolonged period of cold, wet weather which retarded larval feeding and development, resulting in heavy larval mortality. The observations strengthen the previous associations observed between weather and the rise and fall of black-headed budworm populations.

Blood-sucking horse flies and deer flies of the family Tabanidae are important pests of livestock and man in Hastings County, Ontario. In a survey made during 1951-56, immatures of 29 species were collected and reared to obtain information on their insect parasites and other biotic control agents in different habitats. Most of the tabanid specimens were found at five sites where populations were high. The periods of pupation and emergence of Chrysops and of the larger tabanids are shown. The most numerous biotic agents found were two egg parasites, Trichogramma minutum Riley and Telenomus emersoni Girault. Parasites of the larva were a tachinid, Phorostoma novaeangliae (West) and Bathymermis sp., a nematode parasite of Chrysops spp. There were two pupal parasites: Diglochis occidentalis (Ashm.) (Pteromalidae) and Trichopria sp., probably tabanivora Fouts (Diapriidae). There is evidence that both these parasites attack the mature larva of the host.

The egg and five nymphal stages of Apateticus cynicus (Say) are described and illustrated. The nymphal stages can be separated on the basis of head-capsule width, no overlap being encountered in the specimens studied. The overall growth rate was uniform. Varying growth rates were recorded for each antennal segment. Segment one remained the shortest throughout, whereas segment four, the longest in the first stage, became shorter than segment three by the fifth stage. The second segment increased in length from 0.25 to 2.78 mm.

Apateticus cynicus has one generation each year and overwinters in the egg stage in Wisconsin. Females deposit 1-3 egg batches with an average of 57.12 eggs per batch. Hatching in the laboratory took 14 days at approximately 22 °C. The average number of days spent in each of the five instars was 5.08, 5.27, 5.33, 5.0, and 9.5 respectively. Adult females lived up to 163 days and males to 180 days in the laboratory. The effectiveness of A. cynicus in the population reduction of Diprion similis (Htg.) larvae is unknown. Though a large insect and a voracious feeder throughout its immature and mature period, it has low egg production, is univoltine, and overwinters in the vulnerable egg stage, usually on the tree.

Records obtained over a period of six years revealed that the Elaterid beetles in organic soils in southwestern Quebec emerged during the second and third weeks of May when the maximum soil temperature varied between 39 and 57°F and the maximum air temperature between 57 and 80°F. Males appeared earlier than females, the proportion of males becoming larger as the population decreased. Peaks of emergence occurred mostly during the first and second weeks of June when the air temperature varied between 74 and 82°F. Adult populations decreased from the beginning of June to disappear completely by the middle of July. The flight period lasted 73 and 52 days when the maximum daily temperature during the month of May averaged 62.4 and 70°F respectively. Of eleven species, Dalopius pallidus Br., Melanotus communis-fissilis complex and Agriotes mancus (Say) were the most numerous species collected in flight-traps, whereas Dalopius pallidus Br., Hypolithus abbreviatus (Say), Ctenicera tarsalis (Melsh.), Agriotes mancus (Say), and Aeolus mellillus (Say) were respectively the five most abundant species attracted by the solution of dilute molasses in heap-traps. Most of Elaterid beetles were captured when flying south. Beetles were captured at all heights from 15 to 75 inches. The population of adults decreased rapidly after two years of clean cultivation in the area surrounding the experimental plots.

During 1961 and 1962 observations were made on the activities of predators of the pear psylla, Psylla pyricola Förster, in the Okanagan Valley of British Columbia. Attacking the psylla together, the anthocorid bug, Anthocoris melanocerus Reuter, and the green lacewing, Chrysopa oculata Say, gave more effective suppression than either predator alone. DDT and Diazinon drastically reduced numbers of these predators b commercial plantings. In non-sprayed, isolated orchards, trace numbers of these predators maintained effective control of pear psylla populations.

Estimates of the numbers of the western pine beetle, Dendroctonus brevicomis LeConte, in Pinus ponderosa Laws, bark samples were made by radiographs of 25 bark samples and by dissection counts of the bark. High correlations (r = >.9) between the two methods were found for (a) live larvae, (b) live plus dead larvae, (c) live of all stages combined, and (d) live plus dead of all stages combined. The bark dissection method took eight times as long and was 4⅓ times as expensive as the radiographic interpretation method of estimating bark beetle numbers.

Anthocoris dimorphicus n. sp. is described and characters are given to distinguish it from A. musculus (Say). Two species, A. confusus Reut. and nemoralis (F.) are recorded for the first time from North America. A. antevolens White, a common species in western North America, is recorded from Ontario, collected in association with galls of Pemphigini aphids on Populus spp.

During 1960, 534 organisms were collected from 32 nests. In order of decreasing numbers they were ants, bark lice, beetles, mites, sowbugs, springtails, spiders, snails, millipeds, harvestmen, hemipterous nymphs, biting midges, a slug, a damsel bug and a wasp. Observations on their distribution among the nests are included.

Laboratory studies showed that eggs of Hylemya brassicae required 34 and 67 day-degrees at 10° and 30 °C. and 49 day-degrees at 15°, 20°, and 25 °C. to hatch when 7.2 °C. was used as the threshold temperature for development. Factors that were lethal to the eggs were temperatures above 41 °C. for one hour and periods of desiccation of 1, 1, 2, 5, and 9 days at 30°, 25°, 20°, 15°, and 10 °C., respectively.

First-instar larvae survived for approximately 2, 3, 5, and 8 days without food at temperatures of 20°, 15°, 10°, and 5 °C. Starvation for 24 hours immediately after hatching reduced initiation of feeding only slightly.