The effect of any mortality factor on population trend is influenced greatly by other factors that operate contemporaneously within the same age interval, and by the extent to which it interacts with these other factors. A general equation which makes provision for different degrees of interaction is proposed as a simplified first step in the study of interaction, and some theoretical examples are presented to illustrate the importance of the interaction coefficient. Methods for obtaining estimates of the coefficient, both through statistical inference from field population data and through direct observation and experimentation, are discussed.

The species of aphid described here was collected from Sorbus scopulina Greene near Field, British Columbia. It belongs in the genus Nearctaphis Shaposhnikov, and the subgenus Nearctaphis, closely resembling the type species, Aphis bakeri Cowen, but with fused sclerotic plates on the dorsum of the abdomen in the apterous, as well as in the alate female.

Water-stress in young apple trees potted in sandy soil caused a six-fold retardation in Panonychus ulmi (Koch) population growth during two generations in a greenhouse. A considerably smaller retardation effect on the population growth occurred on water-stress trees growing in a compost-sand soil mixture. The leaves from moist compost-sand soil trees contained nearly the same percentage of nitrogen as those from water-stress trees, thus it is believed the detrimental effect of water-stress is caused by the inability of the mites to secure sufficient food supplies for maximum reproduction and growth.

The internal reproductive organs of both sexes are described with regard to their functions during mating and the transfer, storage and use of sperm during oviposition. Although generally hymenopteran in structure they differ in some details from species previously described. The sperm storage organ and glands in the oviducts are more precisely defined and an account given of a structure which regulates the number of sperm entering the sperm bundle prior to its transfer to the female.

During copulation thread-like sperm with helical heads are deposited in bundles of 300 in a funnel-like extension of the oviducts produced by a single contraction of the ovaries. Sperm move along the duct to the sperm capsule largely by their own motility. Sperm remain active in the capsule with their heads toward the opening where they are prevented from escaping by a U-shaped loop in the duct. The loop straightens when ova pass through the oviducts, allowing sperm to descend one at a time. Although the precise mechanism by which the storage organ releases sperm is not fully understood, it is unlikely that discontinuity in the release of sperm is the regulating mechanism involved in the production of haploid males in this species.

The pine gall weevil has a 3-year life cycle on red pine (Pinus resinosa Ait.) in Michigan. Adults oviposit from June to August, depositing 1 to 10 eggs in a niche chewed in the bark of a branch internode. Larvae first emerge in August, feed as a group toward the cambium, and then radiate out along the xylem. Head capsule measurements from 1585 larvae indicate that there are three larval instars. Gall development begins in June of the second year, shortly after the larvae begin the second instar. The third instar commences in June of the third year. Pupation occurs in May of the fourth season; adult emergence follows in June. Overwintering occurs in the egg stage or in the three larval instars. Adults do not overwinter, and apparently three distinct broods occur in Michigan.

A heavily infested egg-bed of Camnula pellucida (Scudder) was severely damaged by the predatory action of Citellus tridecemlineatus tridecemlineatus (Mitchill). This infestation, consisting of an estimated 800 eggs per square foot, was reduced by more than 90%. About half the damage occurred during the autumn after oviposition and half during the following spring prior to hatching.

Egg distribution on a ponderosa pine 14 feet tall of a species of sawfly in the Neodiprion fulviceps complex is presented. Females prefer to oviposit on current year’s foliage. There was no consistency in position of egg cluster on the needle, length of needle, age or size of branch, vertical position in the tree or number of eggs per cluster in needles of different age. Oviposition was highest on south, southeast and east vectors of the tree. Two needles per fascicle were used more often on one-year-old foliage than on current foliage.

Factors inducing diapause and methods foe breaking diapause in the cabbage maggot, Hylemya brassicae (Bouché), are discussed. The pest was reared continuously in the greenhouse during the winter months (when pupae normally enter diapause) by fluctuating the air temperature from 60 to 65 °F. at night to between 75 and 80 °F. during the day and maintaining the soil temperature (in which the eggs, larvae and pupae were reared) at about 68 °F. Pupae produced by flies kept at constant temperatures entered diapause. Fluctuating the soil temperature (for rearing larvae and pupae) did not markedly influence entry into diapause, but when larvae and pupae were reared at above 72 °F. high mortality occurred. Intensity of diapause in the pupae also depended on the temperature at which the flies were reared, with the shorter period of dormancy occurring when flies were kept at low temperatures. Diapause development proceeded more rapidly at 45-50 °F. than at higher or lower temperatures but proceeded to completion at any temperature from 34 to 70 °F. At above about 72 °F., diapause development appeared to be inhibited. The period for completion of development was about 3-8 months, depending on storage temperatures and on intensity of diapause. Preliminary tests indicated that light intensity is a major factor influencing entry into diapause, and results of tests reported in this paper show that this influence can be offset by temperature.

Reproductive rate of the parasite Nasonia vitripennis (Walk.) on pupae of the housefly, Musca domestica L., measured by the number of mature progeny produced per female in 18 hours, decreased with increasing parasite:host ratios. This decrease resulted partly because each female laid fewer eggs, and partly because of increased larval mortality caused by superparasitism. The average number of eggs laid per female was reduced because the parasites wasted relatively more time drilling into unsuitable (i.e. parasitized and previously drilled) hosts on which they subsequently laid few or no eggs; and because the females interfered more with each other while ovipositing. Incidence of superparasitism was greater at higher parasite:host ratios because, in spite of increased interference among the females, there were more simultaneous attacks by two or more females on each fly pupa.

Four species of woodpeckers (family Picidae) are definitely known to be predaceous on the western pine beetle in the Central Sierra Nevada Mountains in California. These are: Dendrocopus villosus, Dendrocopus pubescens, Dendrocopus albolarvatus and Dryocopus pileatus. The red-shafter flicker (Colaptes cafer, Picidae), creepers (Certhiidae), nuthatches (Sittidae), and flycatchers (Tyrannidae) are thought to be predators on the western pine beetle.

Predation by woodpeckers reduced the western pine beetle population by (a) actual consumption of 31.8% in two generations studied, and (b) by increasing parasite densities in the order of 3.85 factor. The increase in parasite density was believed to have been caused by bark removal to a near uniform thickness enabling a higher parasitism by those parasites with short ovipositors, such as Cecidostiba and Roptrocerus spp.

One adverse effect of woodpecker predation was a reduction or a depression of insect predation. Highly mobile insect predators may have been driven away by woodpecker activity, actually consumed, or both.

Bark flakes, chipped or pried off by the woodpeckers during their feeding activity, contained but few insects and it is doubtful that these could survive on the ground and reach the adult stage.

Both sexes of a new species of Sphecomyia from central British Columbia are described. The species is compared with S. pattonii Will. and S. dyari Shan., its closest known relatives.

Ten species of predatory coccinellids representing seven genera were reared from the first-instar larva to the adult stage on dry powdered aphids. Dry pea aphids, Acyrthosiphon pisum (Harr.), and corn aphids, Rhopalosiphum maidis (Fitch), were both superior to bean aphids, Aphis fabae Scop., for growing coccinellid larvae. Though Anatis mali Auct. grew equally well on A. pisum and R. maidis, the larvae generally lived longer when starved after feeding on R. maidis. Dry aphids were as good as living aphids for growing A. mali and Coleomegilla maculata lengi Timberlake. C. maculata grew as well in darkness as in light, and an aphid–pollen mixture was superior to either component alone. Three generations of C. maculata were reared on a yeast diet and this diet is the most promising food for use to supplement natural foods in the field. An arrangement of coccinellid species on the basis of their food specificity does not correspond to the current phylogenetic arrangement, as the taxonomically primitive tribe Coccinellini contains both generalized and selective feeders.

Eight species of Ciconiphilus from the Ciconiiformes and Anseriformes are discussed and illustrated; two of these are newly described: melanolophi. (type-host: Gorsachius m. melanolophus) and cygni (type-host: Cygnus cygnus). New synonymies include: quadripustulatus (Burm.) (= maculipes Gieb., planiceps Piag., cingulatum Piag.); temporalis (Piag.) (= femoratum Piag.); decimfasciatus (B. & L.) (= nyctarde Denny, obscurum Gieb., castaneum Piag., boisduvali Eichler, doriabagla Ausari). C. matosi (Tendeiro) is a new combination. A key is given to the species.

Lecanium cerasifex is facultatively parthenogenetic and deuterotokous whereas L. putmani is arrhenotokous. Males of both L. cerasifex and L. coryli L. failed to fertilize females of L. putmani and in all such attempted crosses the progeny were males.

In the field larvae of L. cerasifex typically settled on the lower surface of leaves and those of L. putmani on the upper surface and this behaviour was influenced by light.

In laboratory experiments L. cerasifex was photokinetic whereas the activity of L. putmani was little affected by light. Both were weakly phototactic but L. putmani appeared to show the stronger phototactic response. It was concluded that the differences in photokinetic and phototactic responses alone were sufficient to explain the location of the larvae on leaves.

Survival of Agrilus liragus B. & B. is highly dependent on host condition. Any weakening factor such as defoliation, mechanical injury, or previous damage by A. liragus increases tree susceptibility to attack and enhances borer survival. The insect itself, through its local weakening effect on the phloem and cambial tissues, controls to some extent its own feeding environment. Although parasitism and predation do take place, the condition of the host tree is considered the prime factor determining the density of the borer population.

That insect flight is influenced by air ions was shown when blowflies, Phoenicia sericata Meigen, were exposed to air ions at ion currents of about 3.4 × 10−11 amp. Positive ions resulted in longer, faster flights than did normal laboratory air, and there were steep increases and decreases in speed. Negative ions resulted in relatively fast, steady flight that usually lasted longer than in positively ionized or in laboratory air. After exposure to positive ions, exposure to alternating polarities resulted in a steady net increase in flight speed but exposure to alternating polarities after exposure to negative ions had no effect on flight.

Maneb (manganous ethylene bisdithiocarhamate) applied topically to Oncopeltus fasciatus nymphs causes death after 7 to 10 days. The gross symptoms of intoxication, histopathology and effect on oxygen consumption are described. Activities such as feeding and walking are slightly reduced after 24 hours and completely inhibited after 3 to 4 days. The tissues most severely affected by the treatment are the secretory cells of the mid-gut epithelium and the cells of the Malpighian tubules. These at first show extreme vacuolization, reduction of the size of cell nuclei and finally cytolysis. Oxygen consumption in vivo is reduced by the treatment.

Measurements of the supercooling points of eggs from different latitudes suggest that the cold-hardiness of N. sertifer is increased by the selective pressure of low winter temperatures. In Ontario, the insect is only beginning to experience temperatures capable of influencing population trends, but the selection of a more cold-hardy population may be in progress. It is predicted that this insect will eventually be capable of extendng its range into natural stands of jack pine in the northwestern portion of the province.

Overwintering eggs are inherently able to supercool to about −26 °C., but exposure to certain non-lethal conditioning temperatures increases their cold-hardiness. Increased cold-hardiness apparently is associated with the appearance of glycerol in the eggs. Mortality curves based on supercooling points of eggs exposed to optimal conditioning temperatures are useful in predicting overwintering mortality of eggs that are not protected by snow cover.

Twenty-five varieties of common wheat (Triticum aestivum L.) and 25 durum wheat (Triticum durum Desf.) grown in the Western Canadian Co-operative Tests were studied at Morden, Manitoba, in 1964, for their resistance to natural infestation by a spider mite, Tetranychus sinhai Baker. Some of these were heavily infested whereas others showed no infestation. The differences were statistically significant. Generally, the commonly grown varieties, such as, Selkirk, Thatcher, Ramsey, Stewart were resistant, but some of the hybrid varieties, such as Sask. 6070, Q2331-5 under test were susceptible.