A rearing chamber designed to test colour preference by biotypes of pea aphid, Acyrthosiphon pisum (Harr.), indicated preferences for orange or yellow or both (615 mμ, and 595 mμ). Aphids of biotype R1 confined to chemical diets back-lighted blue or white survived only for a few days, whereas they lived longer and grew rapidly on diets lighted orange or yellow.

Aedes sierrensis (Ludlow), the western tree-hole mosquito, is the first species of the pulchritarsis-varipalpus group of the subgenus Ochlerotatus which has been shown to have the masculine genotype modified by thermal pressure applied to developing larvae. A rearing temperature of 30.0 °C. during instars 1-3 and the first half of 4, and 31.0° during the last half of instar 4 will modify the degree of masculinity of the palpi, antennae, oral stylets and testes. Modified males are impotent because the genital section fails to rotate to the copulatory position.

The attraction of large numbers of the ornithophilic black fly, Simulium euryadminiculum Davies, to its host, the common loon, Gavia immer (Brünnich), to the place where the loon skin had been washed, and to a dried museum skin of the loon, is described. The fly was not attracted to museum skins of a pied-billed grebe, common merganser and herring gull. The data suggest a system of olfaction in host location, probably involving volatile, air-borne substances. It is possible that the colour or pattern on the head and neck of the loon serves to attract the fly to this area of the host.

In laboratory experiments wettable and emulsifiable malathion and Perthane were most toxic to adult T. vaporariorum and progressively less so to the larval stages in order of development. Eggs were not killed. Perthane was most toxic at low temperatures, malathion at high temperatures. Malathion was more toxic than Perthane and the emulsifiable formulations of both more toxic than the wettable formulations. Against first-instar larvae, at the LD50, level, 70% maneb and 50% Perthane wettable powders were equally toxic but 65% zineb wettable powder was less toxic. Against adults, 70% maneb and 65% zineb wettable powders were one-half and one-third as toxic as 50% Perthane wettable powder at the LD50, level. Tests of spray mixtures against larvae with either 25% malathion or 50% Perthane wettable powders added to either 70% maneb or 65% zineb wettable powders showed neither synergistic nor antagonistic effects.

A nuclear polyhedrosis virus was disseminated into field populations of an incipient outbreak of the forest tent caterpillar, Malacosoma disstria (Hübner). Mortality varied with the concentration of virus used and the age of larvae at the time of spraying. Larvae showed symptoms of infection more rapidly when sprayed with the higher concentrations and secondary infection and mortality occurred in areas where initial mortality developed during the early larval stages.

In the laboratory, the parasitic tachinids Drino bohemica Mesn. and Bessa harveyi (Tns.) made two to four times as many attacks on tenthredinid sawfly larvae exposed on unhealthy as on those on healthy food trees. Olfactory stimuli from the unhealthy trees were preferred by the parasites to those from healthy trees. The possibility of greater masking of stimuli from hosts on healthy foliage than from those on unhealthy foliage was apparently of little importance. In the field a moderate to severe attack by sawfly larvae on a tree will cause the tree to become unhealthy and this increases its attractiveness to the parasites. Thus, the host larvae indirectly assist the parasites to find them. Stimuli that are directly influenced by the health of the food plant of the host may interact with those from other environmental factors in determining the apparent degree of preference by tachinid parasites for different hosts.

Five species of leafhoppers in the genus Erythroneura subgenus Erythridula have been collected and reared on birch hosts in New Brunswick. These species, E. cornipes Beamer, E. sinua Johnson, E. noeva (Gillette), E. aspera Beamer and Griffith, and E. betulaspera Richards and Varty, have similar seasonal histories and habits, but there are differences in their host relationships and ecology. The morphology of adults and nymphs is described and illustrated.

Two new species of Grammotaulius Kol. are described from the North-West of the Nearctic region under the names alascensis and subborealis. Some observations on infra-specific variations in interrogationis Zett. are appended.

The paper of Koenike (1895) on the North American water mite fauna (Abh. naturw. Ver. Brewmen 42: 167-266) and a subsequent revision (Koenike 1912, Trans. R. Canad. Inst. 9: 281-296) together listed thirty-seven species of Hydracarina. These reports were based on materials collected and transmitted to Dr. F. Koenike by the eminent Canadian geologist, Dr. J. B. Tyrrell. Seven of the thirty-seven species were reported from localities in the Rideau Lakes district and in the vicinity of Ottawa.

The Rhagio dimidiatus group in western North America consists of four species, all but one polytypic. Traditional taxonomic procedure has not been successfully applied to this complex, since the component taxa are variable and often poorly defined. Consequently, a quantitative approach, involving deme-by-deme comparison on the basis of the ten most significant differentiating characters, and interpreted in the light of geographic distribution, is used. The group is reviewed, a key presented, and the included forms described. New taxa are: R. maculifer styx, Montana, R. m. byersi, California, R. expansus expansus, Oregon, California, and R. e. franciscanus, California. R. dimidiatus albibarbis (Bigot) and R. maculifer concavus Leonard are given new status as subspecies.

A new species of chalcid belonging to the genus Grotiusomyia Girault is described and illustrated.

Records are presented on twenty nests of Megachile pugnata Say obtained from sumac stick trap-nests. These nests were distinctive as, unlike most Megachile nests, the cells were not constructed from pieces of cut leaf. Instead, the cells were made with basal and apical partitions consisting of leaf discs, chewed leaf materials and soil. Each finished nest contained an empty vestibule and had an orifice plug. The sequences of males and females, and the natural enemies of this species were determined by rearings. Females normally preceded males in the sequence of cells. The species was parasitized by Coelioxys alternata Say and Leucospis affinis Say. The mean number of cells in the nests was 3.5. There is one generation a year in Wisconsin.

The plastics and synthetic fibre materials used in insect traps may acquire and hold an electrical charge that could affect the efficiency of the traps. This became apparent while the Belleville rotary trap (Nicholls 1960) was being used to determine the influence of weather on insect numbers.

Over a period of a few weeks my colleague, Dr. J. A. Juillet, found that one net of the trap consistently caught more parasitic Hymenoptera (sometimes twice the number) than the other. Tests with an electrometer showed that the net of the trap that caught the lesser number of insects carried a negative electrical charge that created a potential difference with respect to ground of 40 volts at one centimetre from the net. Further observation revealed chat the charged net was set slightly higher than the other and that it struck a leaf of a nearby sapling as it rotated. The repeated brief contact was apparently sufficient to cause the net to be electrified. When the leaf was removed the charge on the net gradually dissipated and the numbers of insects caught in the two nets of the trap tended to be equal.

Development time for the parasite Nasonia vitripennis (Walk.) was shorter on young pupae (less than 48 hours old at 24.5 ± 0.5 °C) than on older pupae of the house fly, Musca domestica L. This was primarily because of intrinsic differences between young and old house-fly pupae as hosts. Though less important, two other conditions in young hosts favoured a shorter mean development period for N. vitripennis: first, the smaller proportion of very small parasites, which mature more slowly than the larger ones; and, second, the greater number of parasite larvae per host, which is associated with more rapid development in this species.

The average number of ovarioles in three species of grasshopper reared in the laboratory was: Melanoplus sanguinipes (F.) 28.1 ± 2.4, M. bivittatus (Say) 80.1 ± 10.1, and Camnula pellucida (Scud.) 27.6 ± 2.7. Not all ovarioles developed mature eggs; some eggs were resorbed. The number of egg rudiments in the ovarioles increased somewhat with age of the grasshopper and would not limit the number of eggs laid. Some abnormalities are described and some discussion of the corpus luteum is included, particularly the relationship between a pigmented corpus luteum and ovulation.

Experiments show that A. tepidariorum selects sites for web building by a series of movements that are random with respect to the distribution of its prey. If selected sites fail to yield an adequate supply of prey they are quickly abandoned. If adequate supplies of food are forthcoming at a site, random movements cease and the site is systematically searched by filling the area with web. Light plays no part in the selection of web sites, but other extrinsic features, for example air currents, play an important role.

Female black flies may be sorted into two age groups, the nulliparous and the parous, by the changes in the ovary including the absence or presence of follicular relics. This highly accurate method, developed in Russia and England for Anopheles mosquitoes (Beklemishev 1944; Lewis 1958a), has been recently adapted for use with black flies (Lewis 1958b; Davies 1961).

A pictorial representation of the gut of the green peach aphid, Myzus persicae (Sulzer), is shown based on dissection, light microscopy, and electron microscopy.

The sucking pump is crescentic in cross section with a thick, rigid, posterior wall and a thinner, flexible, anterior wall. Dilator muscles arise on the clypeus and are inserted along the midline of the anterior wall of the pump chamber. Morphologicael evidence of the sucking action of the pump is included.

A new species of Metapolophium is described, this being the first record of the genus from the Canadian arctic.

The genus Alipumilio, previously known from a single female from the Amazon, is recharacterized. Three new species from Peru and Mexico are described and a key to the four known species is presented.