The possibility of imperfect coincidence between the appropriate stages of Neodiprion sertifer (Geoff.) and two of its important parasites was demonstrated. One of the parasites, the indigenous ichneumonid Exenterus canadensis Prov., which attacks late-stage larvae, has good spatial coincidence; but some members of each generation suffer from imperfect temporal coincidence, or asynchrony, caused by the interaction of temperature influence on parasite development rate and temperature variability between development sites in the litter. The second parasite, Pleolophus basizonus (Grav.), is an introduced, multivoltine ichneumonid cocoon parasite. It may be imperfectly synchronized in its first generation each year and may show imperfect spatial coincidence in all generations through its inability to attack host cocoons beneath approximately 1 in. or more of litter.The intricate relations between parasite and host density, time, attack, and coincidence were investigated using the basic functional response submodel developed by Holling, a submodel that describes changes in oviposition behaviour with time, and a submodel that predicts the number of hosts attacked, given the number of eggs laid and data on the distribution of eggs among hosts. In the two species studied, the effect of asynchrony in one generation cannot be considered without considering the influence of superparasitism. At low host densities, superparasitism largely buffers the effects of decreased synchrony. This buffering effect decreases as host density increases until when each parasite is attacking all the hosts it can, it is almost eliminated. Imperfect spatial coincidence in one generation merely lowers the usable host density. Thus its effect can be seen in the functional response of the parasite to host density. When host–parasite interactions over 25 to 35 host generations were simulated, using initial conditions resembling those ensuing when small numbers of both host and parasite invade a previously unattacked stand, populations became stable after passing through one or more oscillations. Decreasing temporal or spatial coincidence increased host and parasite densities at the peaks of oscillations and increased the ultimate steady density of host and parasite, until coincidence was reduced to nearly half. At this level, the host escaped the regulating ability of both species of parasites.

DDT and DDD emulsifiable formulations were tested against aquatic invertebrates in small plots in rapids in the St. Lawrence River. Pollution was minimal; less than 0.0044% of the river discharge was treated in each rest.The weakest dosage of DDD, 0.8 p.p.m.-minutes, disabled many Trichoptera and Diptera; the strongest, 12.0 p.p.m.-minutes, did not eliminate any one Order of insects except perhaps Plecoptera. A dosage of 6.0 p.p.m.-minutes was selected for tests on a larger scale against shadfly larvae (mainly Trichoptera). Net-spinning Trichoptera were more sensitive than case-bearers. Of the non-insect organisms, amphipods were relatively sensitive but their populations were rapidly restored by immigration. Oligochaetes and molluscs were least affected.The use of small plots in a large river required special equipment and techniques: a larvicide dispenser (to be described separately), the use of concentrated milk as a dye to aid in the survey of plot boundaries, the transfer of disabled organisms to fresh water to compare recovery rates, and a formula combining data from samples of both disabled and surviving organisms to estimate per cent kill.

Data presented demonstrate that induction of pupal diapause in the cabbage maggot, Hylemya brassicae (Bouché), involves a relationship between photoperiodic, temperature, and light intensity conditions provided for the flies, eggs, and larvae. Generally, a short daylength of 12 hours for the flies induces pupal diapause, whereas a 16-hour photoperiod dictates continuous development without diapause. However, the expected response can he partially or almost completely reversed depending upon, conditions of photoperiod and temperature provided for eggs and larvae. Decreasing temperatures combined with low light intensities and short photoperiods for flies and larvae cause almost all pupae to enter diapause, and high temperatures tend to offset the influence of a short daylength or a downward trend in photoperiodic exposures provided for the flies and larvae. Diapause development proceeds to completion at a wide range of temperatures but high levels at certain times result in high mortality. Growth development following the completion of diapause development is inhibited by temperatures above 22 °C, whereas the final or adult developmental stage continues to completion at an increasing rate with increasing temperatures.

The larvae of 11 species of the genus Stenoporpia (Geometridae: Lepidoptera) from Arizona are described, figured, and keyed. On the basis of the known larvae, Stenoporpia can be divided into four very distinct species-groups, one feeding on species of oak, and the other three on conifers. Temporal displacement was found in four species of Stenoporpia feeding on ponderosa pine at the Fort Valley Experimental Forest near Flagstaff, Ariz. The sensory papillae of the maxillary palpi are investigated as a taxonomic character. A list of all of the known foodplants of the species of the genus is given.

High mortality occurred in the blood-sucking bug Rhodnius prolixus Ståhl after feeding through an artificial membrane on defibrinated mammalian blood containing injectable antibiotic mixtures.

The uric acid content of the fats and the whole organism was determined by the Technicon spectrocolorimeter method for all instars of healthy and nuclear-polyhedrosis-infected larvae of Neodiprion swainei Midd. The results obtained revealed that (a) in healthy larvae the uric acid content gradually increased from 20 to 470 p.p.m. from the first to the fifth instar inclusively and (b) in virus-infected larvae the uric acid content was always greater than in healthy larvae. It increased from 21 to 493 p.p.m. from the first to the beginning of the fourth instar, reached a maximum of 830 p.p.m. at the end of the fourth instar, and decreased to 680 p.p.m. at the fifth instar.

Longevity and fecundity data are presented for cohorts of cabbage aphid, Brevicoryne brassicae (L.), reared on different hosts (Barbarea vulgaris, Brassica pekinensis, and two varieties of Brassica oleracea) and under constant and fluctuating environmental conditions. Changes in fecundity and development were the chief causes for the different rates of population increase (r) observed on each host. Alate forms developed only in the cohort reared on B. vulgaris, the most resistant host studied. Host factors, acting during the late prenatal period or during postnatal development, appear to be capable of influencing form determination in this aphid.

Both laboratory-reared and field-collected pupae of the pine butterfly, Neophasia menapia F. and F., exhibited varying degrees of dark pigmentation. Most of the pupae, however, lacked this characteristic. Pupal coloration was not due to sexual differences, parasitism, or the quantity of food available during development. Although light was necessary for pigment formation, the effect was nullified by providing light-green foliage or a white background for the larva on which to pupate. Dark-green foliage of the previous growth year had an intermediate effect. Larvae that pupated on twigs or against a black background developed heavy pigmentation.

The Nearctic species of the genus Atrometus Foerster (Hymenoptera: Ichneumonidae) north of Mexico are revised. Three previously recognized Nearctic species, A. praediscae, A. clavipes, and A. evetrivorus, are synonymized with A. geniculatus Holmgren from the Palearctic Region. A new species A. badius and a new subspecies A. geniculatus obscurus are described. A key is presented for the separation of the species and subspecies.