Eighteen species are listed of which eight are described as new. Most of these species were collected in the more southerly parts of the Canadian Arctic, but two species were collected at Lake Hazen which is situated in the extreme northeastern portion of Ellesmere Island. The majority of the species belong to well known Holarctic genera. Characteristically Palaearctic groups are represented by five species, but exclusively Nearctic groups are represented by a single species. The most conspicuous biological feature is the apparent reversal of the switch mechanism governing the production of sexuales since, in spite of the excessively long photoperiod, oviparae are common.

During a study on the population dynamics of the gypsy moth, Porthetria dispar (L.), conducted in the Town of Glenville, New York, some factors were found to affect the sexes differentially. The importance of this differential mortality is indicated by the fact that 78 per cent of the variation in the logarithm of an index of population trend (the ratio of population density from year to year) was associated with the logarithm of adult sex ratio.

Disease and desiccation during instars IV-VI and among pre-pupae were strongly selective against the female insects. This differential mortality caused a change in the pupal sex ratio from about 70 per cent females where no disease occurred to less than 25 per cent female pupae following an epizoötic. Ichneumonids, on the other hand, usually killed more male pupae than females, except when host size was reduced by excessive larval density and competition. The net result from this series of factors that distort the sex ratio has been to produce adult sex ratios varying from more than 80 per cent female moths to only 2 per cent females.

In this host species, as in most other animals, it seems that the population consequences of a mortality factor that kills the host sexes in different proportions should be evaluated in terms of the more critical (female) sex destroyed.

Parasites of the sawflies Neodiprion abbotii (Leach), N. abietis (Harr.), N. lecontei (Fitch), N. nanulus nanulus Schedl, N. pinetum (Nort.), N. pratti banksianae Roh., N. swainei Midd., and the N. virginiana Roh. complex are separated by using characters of the parasite remains in the host cocoons from which the parasites emerged. Characteristics of the cast skin of the last larval instar of 11 species are described and illustrated in this paper; the remaining 29 species were described and illustrated in earlier papers (Finlayson, 1960a, 1960b, 1962). Keys are given to separate the species of the genera Exenterus and Lamachus that attack the above hosts, using characters of the cast skin of the last larval instar.

The genus Ips is one of four closely related genera in the tribe Ipini, sub-tribe Ipina (De Geer 1775, Balachowsky 1949, Nunberg 1954, Hopping 1963). There are now 32 species of Ips recognized in North America, with a few more as yet undescribed. This paper defines the groups of closely related species with observations on the group relationships of species from other parts of the world. Work is in progress to define the North American species in each group.

This paper presents a key to the larvae of six species of lepidopterous needle miners on pine in Ontario, namely, gelechiids Recurvaria canusella Free., R. coniferella Kft., R. resinosae (Free.) (n.comb.), and Exoteleia pinifoliella Cham.; and yponomeutids Ocnerostoma strobivorum Free., and Ocnerostoma sp. Complementary information is given on distribution, hosts, biology, and parasites of each species.

Height growth and number of side branches developing the first growth season after chemical suppression of the European pine shoot moth, Rhyacionia buoliana (Schiff.), were measured on 40 treated and nontreated plots of red pine, Pinus resinosa Ait., in Michigan. Some plots had been treated during the summer-treatment period and some during the spring-treatment period. Summer treatment increased the height growth and number of side branches over no treatment; the degree of chemical suppression was useful in estimating tree growth during the following growing season. In contrast, spring suppression had no effect on height growth and number of side branches.

Many problems in the management of renewable natural resources are extremum problems: we wish to maximize fish yield from a lake, tree yield from a forest, or minimize insect pest survival, for example. Such problems can be handled better by dynamic programming than classical analysis, because of the large number and the complex nature of constraints imposed on such systems. However, a priori arguments and analysis of biological time series show that such renewable natural resources do not constitute Markov processes, since state changes from t to t + 1 are dependent on the state: at t − 1 as well as the state at t. Therefore, before making a decision about the optimal strategy at t, we must explore the future consequences of the strategy at t + 1 and t + 2. This paper reports computer experiments on strategy evaluation procedures, using dynamic programming and modified dynamic programming with two-stage “look-ahead”. The data used to develop the model came from 60 years of observations on weather conditions and insect pest populations at Magdeburg, Germany. The general conclusion from this work is that the selection of most appropriate strategy for a biological management problem should he determined by the structure of the problem. Sometimes, “one-stage look-ahead” gave the lowest value for the criterion function, and sometimes “two-stage look-ahead” was optimal. The two types of programming always yielded lower cumulative defoliation than the method now used: killing as many pests as feasible whenever “pest” densities are reached.

Although Rhopalosiphum padi L. was common on cereals and Gramineae in Ontario, only a small number of R. fitchii (Sand.) were found on one grass plant in 1961. Fundatrigeniae of R. padi from Prunus virginiana L. and of R. fitchii from Crataegus spp. and Malus spp. were transferred to oats and wheat on which alienicolae of R. padi multiplied rapidly, but R. fitchii very slowly. R. fitchii transmitted all but one of the isolates of barley yellow dwarf virus (BYDV) that R. padi transmitted to Clintland 60 oats, but fewer test plants became infected, the incubation period for symptom development was longer and symptoms were less severe when R. fitchii was the vector. Both species infected more test plants after a 5-day than after a 2-day acquisition feed on the virus source. It appears that R. padi, a common and efficient vector of BYDV, has frequently been mistaken for R. fitchii which is not common on cereals and not a highly efficient vector.

A dosage concept is proposed to explain differences in vector efficiencies of R. padi and R. fitchii. It is also suggested that strains of BYDV become ’adapted’ to transmission by a vector species.

In the vicinity of Douglas, Arizona, male Protoxaea gloriosa were noted establishing territories as early as July 16, 1962, although the principal emergence of both sexes occurred on July 26 and 27, following the first soaking summer rains. The territories involved flowering plants which were guarded during the morning hours, primarily between 7 a.m. and 11 a.m., against all other insect intruders except females of their own species. Guarded plants included those visited by females for nectar, or pollen, or both, as well as plants which they were not observed to visit at any time. Newly emerged females make their first flights during the morning hours in search of nectar for their own use. Male territorial behavior increases the probability of immediate mating with these virgin females. Mated females apparently lose their attractiveness to males and are allowed to visit guarded plants without interference. Such females collect pollen between 6 a.m. and 9:30 a.m., primarily from Solanum, and nectar up to about 11:30 a.m., primarily from Asclepias, Verbesina and Larrea. Male belligerence toward other bee visitors to these plants reduces actual or potential competition for pollen and/or nectar, as the case may be. After leaving their territories late in the morning, the males seek nectar for themselves, and later in the afternoon gather gregariously in large “balls” for “sleeping”, in marked contrast to their earlier intolerance of one another.

Most species of grasshoppers in North America appear to lay their eggs in soil or among grass roots. A variation of this habit was reported in Manitoba by Criddle (1933) who states that Chloealtis conspersa Harr. and Neopodismopsis abdominalis (Thom.) oviposit exclusively in decaying wood or in dung.

Recently, a few stems of sweet clover, Melilotus alba Desv., and Russian thistle, Salsola kali L. var. tenuifolia Tausch, that contained insect eggs, were sent to the Saskatoon Research Station by A. Vadeboncoeur of Val Marie in southwestern Saskatchewan. These eggs were laid in the pithy centres of the stems in groups of eight or nine (Fig. 1). According to the sender, the clover had been cut during the summer and the thistle was about two years old. Both were lying in the ditch on the railroad right-of-way. At our request, Mr. Vadeboncoeur sent in a few more infested stems. From a total of about 10 samples it seems evident that oviposition in plant stems is typical of the grasshopper involved. The exact egg-laying procedure is difficult to visualize in view of the small diameter of the pith (approximately 3 mm.), and the lack of any sign of penetration through the side of the stem. Inserting its abdomen into the narrow stem and depositing the eggs 25 to 30 mm. from the cut end of the stem must have involved considerable gymnastic manoeuvring by the female grasshopper.

With winged and wingless males being currently found in Southern Quebec, the pea aphid, Acyrthosiphon pisum (Harris), cannot be regarded as a subspecies of the European species, on the basis of males being supposedly winged in North America and East Africa and wingless in Europe and Asia. The host relationships are apparently different as is also the occurrence in Europe of red forms of the aphid.