This paper is the first of two concerning overwintering of shallow-pond Chironomidae in regions with cold winters, and deals with winter habitat conditions as a background to a later report on chironomid biology.

Some observations on winter temperatures and factors affecting them, especially in terms of whether freezing occurs, are given for shallow ponds near Ottawa, Ont. (45° N.), where mean air temperatures are about −10 °C for the 3 months of midwinter. Ice thickness was inversely proportional to the depth of overlying snow. The high snow cover on a sheltered pond prevented thick ice from forming and the bottom temperature at a depth of 25 cm remained near +2 °C throughout the winter. Up to 40 cm ice occurred on an exposed pond where snow was largely blown away. Maximum ice thickness was not reached until mid-January. The mud surface at a depth of 15 cm froze only on 22 December and at a depth of 25 cm not until 11 January. The minimum temperature near the margin (at a depth of 15 cm) at the mud surface was −2.6 °C, and 5 cm into the mud was −1.7 °C. In 1969 abnormal rainfall in November increased the pond level by over 30 cm just prior to freezing. Of the area subsequently frozen down to the bottom, three-quarters had been dry in the summer. The frozen portion represented 61% of the total pond area.

The winter features of shallow pond environments as winter habitats in north temperate regions and in the arctic are reviewed. In north temperate regions, there is great variability in terms of freezing, produced by a complex of interactions between local topography, precipitation, and air temperatures. The minimum in the least favoured areas, maintained for a relatively short period, is only a few degrees Centigrade below freezing, and often considerable areas remain unfrozen especially in sheltered habitats. Part of most summer-permanent habitats remains unfrozen except in unusually severe years. Winter conditions are ameliorated beneath ice and snow insulation by heat stored in the earth below; solar radiation is probably of little importance. Winter stagnation with exhaustion of oxygen may occur in unfrozen areas beneath ice cover, together with increase of concentration of solutes. In the arctic, ponds up to about 1½ to 2 m deep are frozen to the bottom. Minima in the bottom mud may reach −20 °C or −30 °C for several months depending on latitude and on local topography.

A technique for ageing cocoons of Neodiprion sertifer (Geoff.) is outlined using the redox dye 2,6-dichloroindophenol. New cocoons reduce 1 ml of a 0.001% solution in 85% ethanol from blue to colorless in 15 minutes. This reducing power diminishes with age.

Nine new species of Forcipomyia are described in all stages, two belonging to the subgenus Proforcipomyia, five to Forcipomyia s. str., and two to Trichohelea.

Protein fed to adults of the carrot rust fly, Psila rosae F., enhanced oviposition: the addition of yeast hydrolysate to the sugar diet resulted in a 50% increase in oviposition, giving an average of 75 eggs per female.A description is given of a simple oviposition device, which allows normal oviposition (compared with sand).Carrots planted in sand gave best rearing results when inoculated with eggs 14 days after insertion. Germinating carrot seeds placed on top of the sand improved the rate of development of the eggs to pupae from 40% to 62%.

The morphology and histology of the sex pheromone-producing gland in the females of Choristoneura fumiferana (Clemens), C. pinus (Freeman) (Tortricidae), and Malacosoma disstria (Hubner) (Lasiocampidae) is reported. A review of the literature relevant to such a study is presented in tabular form.

The rye jointworm, Harmolita secale (Fitch), caused economic damage to fall rye in Alberta in 1968, 1969, and 1970, a first such record for Canada. Infested stems reached an average of 21 galls. Individuals in the laboratory required added moisture for pupation and to facilitate emergence of adults, which occurred during the first week of June in 1970. In 1970, the reproductive potential of about 70 was more than counterbalanced by the failure of almost 90% of the galls to produce adults.

Evidence is given in support of the hypothesis that the spatial arrangement of attacks by the mountain pine beetle (Dendroctonus ponderosae Hopk.) on its host, lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.), is largely determined by the pattern of bark niches suitable for attack initiation. Density of attack sites and bark thickness are important in determining the attack-harbouring potential of the bark and in determining the upper limit of attacks, thus, the potential area available for attack on the bark surface of lodgepole pine trees. At fixed levels on the clear bole of naturally infested trees, attack pattern tends to be regular owing to the regular spatial pattern of suitable attack sites. The regularity of the attack pattern is disturbed by the presence of an attack-density gradient around the stem circumference. The vertical attack-density gradient over the host is well described in terms of a relation between attack density and bark thickness. This relation is asymptotic and rests on the assumption that the density of bark niches suitable for attack initiation approaches an upper limit with increasing bark thickness on lodgepole pine trees.

A survey of the insect pests of carrots was conducted in the organic soils of southwestern Quebec with a view to establishing the presence of the carrot weevil, Listronotus oregonensis (Lec.), in this province as well as to confirm the importance of other pests damaging carrot crops. Four different methods were used to capture adults, and the root sampling method was used for establishing larval populations.The carrot weevil was captured by light trap for the first time in Quebec on 1 June 1967, but was neither recognized nor identified until June 1970 when a few specimens were obtained again by light trap set at Ste. Clotilde and by colour traps placed in the experimental fields used for the survey in 1970. Damage caused by this new pest on carrots ranged from 2.0% to 22.0% root injuries throughout the carrot growing areas of the organic soil regions of Sherrington, St. Michel, and Ste. Clotilde representing several thousands of acres. The carrot rust fly, Psila rosae (F.), was the only other carrot pest captured, but has been found to be of no importance in these areas.

Experiments on an anautogenous strain of Culex pipiens L. failed to support the theory that sustained gut stretching initiates egg development by anautogenous mosquitoes. The stomach expanded in females fed sugar after the anus was sealed, but eggs did not develop. Also, the ovaries were not activated by an enema of agar which congealed in the stomach and kept it distended. Development of eggs by females given enemas of γ-globulin or egg albumen was presumably an ovarian response to nutrient; development of eggs by some females that received nutrient (amino acids) by direct injection into the haemocoele supported this interpretation. When 1, 4, 7, and 10% egg albumen or γ-globulin were supplied as volumetrically equal enemas, response to 1% was least (few eggs matured and these by only a few females), but was greater with increased amounts of nutrient. It is proposed that certain mechanisms permit the mosquito to evaluate the nutrient potentially available in a blood meal before its complete digestion and to start maturation of an appropriate number of eggs.

Some aspects of the characterization and delimitation of the chironomid genera are presented. The size and composition of the taxa and different types of splitting are discussed, with examples from Chironomus. Some opinions regarding the practical value of the category subgenus are weighed. Ideas about the relationship between phylogeny and classification are put forward, and some problems concerning the ecological characterization of genera are discussed.

Internal cone temperatures recorded in the mornings and in the afternoons demonstrated marked differences between sunny and shaded sites. Analysis of variance confirmed differences between treatment as highly significant. High and low cone temperatures coincided with high and low ground temperatures. The average correlation coefficient relating cone and ground temperatures was highly significant, while that for cone temperatures and cone size was non-significant.

Heavy insect mortality occurred in cones exposed to direct solar radiation but mortality remained relatively low in the cones left in the shade. The greatest high-temperature mortality occurred during summer between late June and early August.

Flights of green peach aphid alatae were recorded in suction traps and on trap plants from 16 May to 4 December. Four peaks of flight occurred in each of the years 1967–70, in early June, early July, late August and late September, the third being the largest. The aphid flew in very large numbers during August. There was a very significant correlation between the weekly catches from a suction trap and a group of Brussels sprouts trap plants at the same location and between two suction traps 3.2 km apart. By both methods the average weekly catch for 1967 > 1970 > 1969 > 1968.

Tetrastichus incertus, a parasite of the alfalfa weevil (Hypera postica) larva, occurs throughout the northeastern United States, including almost all of New York. Field studies in 1967 and 1968 indicated that the parasite and its host were not closely synchronized in New York; the parasite was uncommon in June when hosts were abundant while the opposite was true in July. In 1966 and 1967, the proportion of parasites entering diapause increased throughout the summer, from 1–31% in June to 67–100% in September. Therefore, most parasites produced in June, when hosts were abundant, emerged in July when hosts were scarce. Winter mortality among parasites in diapause was high (51–64%) in field cages. The survivors of the overwintering generation of T. incertus constituted a small fraction of the annual production of parasites.

In the laboratory the offspring of older T. incertus tended more to enter diapause than did the offspring of younger parasites. This indicated the incidence of diapause may be correlated with host availability; when hosts are uncommon, diapausing parasites are produced.

Field and laboratory data indicated a ratio of one T. incertus to eight alfalfa weevil larvae would be necessary to achieve 50% parasitism of the host population. Such a host:parasite ratio never occurs when the hosts are common.

Twenty-one sympatric species of Carabidae fed on eggs of Euxoa ochrogaster Guenée in laboratory trials. Seven species were demonstrated to have fed in the field on cutworms or pupae of E. ochrogaster and six species fed on cutworms in the laboratory. Carabidae are important as predators of E. ochrogaster but failed to eliminate the prey population in a study area in central Alberta.

The sex pheromone of the female eastern spruce budworm was identified as trans-11-tetradecenal by a combination of electroantennogram techniques, laboratory bioassays, and chemical analysis. Subsequent field trapping showed that this compound is a potent attractant for both male Choristoneura fumiferana (Clem.) and C. occidentalis Free, thus supporting its identification as a sex pheromone of the eastern spruce budworm and suggesting that it is also a major component in the pheromone system of C. occidentalis.

It was observed that the parasite Dahlbominus fuscipennis Zett. was infected when developing in microsporidian-infected pupae of Neodiprion swainei Midd., Neodiprion lecontei Fitch, Neodiprion pratti banksianae Roh., and Pristiphora erichsonii Htg. The microsporidian was observed in the whole gut epithelium, fat body, and cerebral ganglial cells of the parasite. The parasitoid was infected only after the hosts had completed their winter diapause or at any time in non-diapausing species.

Notes are given on type material of 25 nominal species either referable to the genus Sphaerophoria or described in that genus and referable to the genus Ischiodon. Lectotypes are designated for 15 of these species. New synonymy is indicated for 13 nominal species on the basis of examination of type material and for three other nominal species on the basis of published figures of male terminalia of type material. One species frequently referred to the genus Sphaerophoria is transferred to the genus Allograpta.