Three new species are described; two European species, tringarius L. and lineola Fabr., are recorded for the first time; and the previously described species are redefined and new distribution records presented, with a key to the eastern species. Rhagio hirtus Loew is recognized as a good species, R. boscii Macquart and Xylophagus fasciatus Say are synonymized with albicornis Say, and R. intermedius Walker is synonymized with R. vertebratus Say. The three new species are R. dichromaticus from Louisiana, recognized by its extremely dark coloration; R. floridensis from Florida and Georgia, with yellow thorax and distinctively patterned wings; and R. orestes from Great Smoky Mountains National Park, which is close to hirtus but separable by the darker thorax and abdomen.

Plots in a bearing apple orchard were sprayed with formulations of Bacillus thuringiensis Berliner on five to seven occasions in each of four consecutive seasons. Larvae of the winter moth, eye-spotted bud moth, orchard tent caterpillar, and fall webworm were less numerous on foliage in plots treated with B. thuringiensis than in the check plot. Numbers of free-living blister mites were reduced by treatment with the bacterium. Other phytophagous mites were not numerous in any of the plots. Injury to fruit by larvae of the codling moth, winter moth, and eye-spotted bud moth and by the mirid Atractotomus mali (Meyer) was lower in plots treated with the bacterium. Only three taxa of predacious arthropods were consistently affected by the application of B. thuringiensis; one was less numerous where the bacterium was applied and two were more numerous.

Ips calligraphus (Germar), I. ponderosae Swaine and I. interstitialis (Eichhoff) represent one variable species with the oldest name, Ips calligraphus (Germar) taking precedence. Ips calligraphus can always be recognized by the six spines on each side of the declivity. All other species in North America have less than six spines on each side.

Large numbers of Oriental fruit moth adults were successfully tagged (500 or more counts per minute) by holding them for 24–48 hr. in cages provided with cotton wicks moistened with a water-solution of P32 at 20 microcuries per millilitre. The addition of sugar to the tagging solution did not increase its effectiveness. Approximately 80% of the total radioactivity of the tagged moths was internal due to ingested liquid and the remainder was on the surface of their bodies; 73% of the total was in and on the abdomen. The loss in radioactivity of tagged moths in 1–6 days was 2.2–4.7 times greater than the theoretical loss due to isotope decay alone. The highest rate of loss occurred during the first day, probably through excretion before the P32 was absorbed from the digestive tract. Egg laying contributed to loss of radioactivity. Though water and liquid bait removed some P32 from tagged moths this did not result in appreciable contamination of other moths trapped in the liquids.

Attempts to tag large numbers of moths (400–1000 per cage) for release and recovery experiments were only partially successful as the radioactivities attained by individual moths varied widely at different times and from cage to cage, even under the same environmental conditions. This appeared to be partly due to differences in the feeding behaviour of different batches of moths and it may have been influenced by the conditions under which they were reared.

This study confirms an earlier finding that the oystershell scale, Lepidosaphes ulmi (L.) is normally controlled in Nova Scotia apple orchards by the aphelinid Aphytis mytilaspidis Le B. and the predacious mite Hemisarcoptes malus (Shimer). The effectiveness of the former may be limited in colder areas by low winter temperatures, and both species are detrimentally affected by some spray chemicals. The evidence presented indicates that either A. mytilaspidis, or H. malus, or the two of them together, may operate as key-factors in regulating the density of oystershell scale populations.

The divergens group of the genus Euxoa Hbn. is defined, and a new species, Euxoa sinelinea, is described from Goose Bay, Newfoundland, and from Smoky Falls and Black Sturgeon Lake in north-central Ontario.

Tests on adults of the migratory grasshopper, Melanoplus bilituratus (Wlk.), showed carbaryl (1-naphthyl N-methylcarbamate) to have a very marked negative temperature coefficient of toxicity. This was believed to be due to a rapid increase in the rate of detoxification at higher temperatures. The marked synergistic effect of piperonyl butoxide, believed to act by blocking the detoxification process, appeared to confirm this.

The acceptability of host plant extracts on pith, charred filter paper, and an agar diet, and vacuum infiltrated into lettuce leaves was compared on three species of Lepidoptera and two of Coleoptera. The vacuum infiltrated lettuce was eaten by two of the Lepidoptera and it was the only method acceptable to the Coleoptera. The agar diet was eaten by the three Lepidoptera while pith and charred filter paper were acceptable to only two of them. It is concluded that vacuum infiltration of lettuce leaves is a useful method for the bioassay of host plant extracts to determine if they contain insect feeding token substances.

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.

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.

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.

Sisyphus submonticolus n. sp. is described from Durango, Mexico, and compared to the only other New World species, S. mexicanus Harold.

An insect emergence trap for quantitative studies in shallow ponds is described and figured. Details of its operation are given.

Examples and data based on the host-parasite complex of the California red scale, Aonidiella aurantii (Maskell), and its parasites in untreated test plots in the citrus areas of southern California, not including the San Joaquin Valley and the desert areas, show the following: (1) Weather does not impose upper limits to host population increase. (2) In areas of favorable weather, certain parasites regulate host population densities at very low levels, other factors also being favorable. (3) The parasite Aphytis lingnanensis Compere is affected by weather differentially with respect to the host, and to varying degrees in different localities. The effects of field weather for each 2-week period of the year on all stages of this parasite individually as well as on population growth in held experimental cages are discussed. Adverse effects of weather on the parasite preclude successful population regulation of the host by the parasite at certain times or in particular areas but the range of the parasite is not restricted. (4) Another parasite, Comperiella bifasciata Howard, has its range restricted by weather and not by competition with other parasites to intermediate and interior citrus growing areas. It is never found along the coast. (5) Yet another parasite, Prospaltella perniciosi Tower, has its range restricted by competition and not by weather although it gives the appearance of being restricted by weather because it occurs only in coastal districts. (6) Examples are discussed of interactions between weather and dust, ants, or chemicals with parasites and hosts which result in various modifications of the abundance of the host and parasites. (7) Examples are discussed of the effect of weather on interactions between competing species of parasites and the host which have resulted in striking modifications of the previous distribution of certain parasites.

Osmia atriventris Cr. and Megachile relativa Cr. are the most abundant bees accepting trap nests in the Black Sturgeon Lake area of Ontario. Hylaeus ellipticus (Kby.), H. verticalis verticalis (Cr.), Hoplitis albifrons albifrons (Kby.), and H. cylindrica (Cr.) are common while Hylaeus basalis (Sm.), Osmia proxima Cr., M. inermis Prov., and M. gemula Cr. are comparatively rare. All except Osmia atriventris are univoltine and overwinter as prepupae. O. atriventris is both univoltine and biennial. The major flight and nesting period for all bees is during July although M. relativa is active throughout August. Hylaeus spp. construct nests of silken membranous, secreted materials; Hoplitis spp. utilize macerated plant materials and pebbles to divide their nests; Osmia spp. partition their nests with macerated green plant material; and Megachile spp. line and plug their nests in typical leafcutter fashion. All bees provision their nests with pollen moistened with varying amounts of nectar. The sexes are probably almost equally divided in all species. Major parasites are Gasteruption assectator assectator (L.) for Hylaeus spp.; Chelynia subemarginata (Cr.) for Hoplitis spp.; Sapyga sp., for Osmia atriventris; and Coelioxys modesta Sm., and C. lucrosa for Megachile relativa. Melittobia chalybii Ashm. destroyed a few cells occasionally.

In certain insects there exist eocrepuscular diel periodicities of activity in which the sunrise peak occurs at a higher light intensity than does the peak at sunset. This may happen because the indicator-process chosen by the observer to designate the activity is not the first in a behavioural sequence released by light of a critical intensity.

The construction of a temperature gradient area based upon a heat exchange grid is described. The main feature of the gradient apparatus is that it provides a flexible, yet temporally stable and evenly sloped gradient, which can be maintained in replicated troughs for many months with minimum attention. The control of the R.H. gradient in troughs containing a food medium is also discussed. Data relating to the life histories of Tribolium examined in the gradient is offered to exemplify the type of results obtainable.

Community organization is defined as the mean number of trophic links connecting species of different trophic levels in a community. For the special purposes of this paper, competition is assumed to occur whenever two species are known to eat the same food species. Community stability is defined as the reciprocal of the mean, for all species, of the standard error of logarithms of annual collection sizes. It is thus a measure of stability over time of the species populations in a community. Several authors writing about the relationship between community organization and community stability have insisted that the stability of a complex ecological system increases with the number of avenues by which energy can flow through it. This theory does not seem consistent with the observation that some insect pest species of notorious instability are attacked by a great number of entomophagous species. In this paper we seek additional evidence bearing on the relationship between community organization and stability, using computer analysis of data collected by the Canadian Forest Insect Survey on forest Macrolepidoptera and their food plants. After considering our results, and those of other workers, we postulate the following hypothesis. Stability at any herbivore or carnivore trophic level increases with the number of competitor species at that level, decreases with the number of competitor species that feed upon it, and decreases with the proportion of the environment containing useful food. If this hypothesis is valid, too much competition in the entomophagous trophic level will not allow the species in that level to be instable enough to control an unstable pest. Therefore, the best type of biological control agent is one that has no direct competitor species. Also, the most unstable biological control agents, and hence those capable of controlling an unstable pest, will be polyphagous.