Two of the most important factors that contribute to the success of a parasite population are (1) the ability to find hosts and (2) the ability to oviposit in hosts when found. The theories of Thompson (1922, 1924), Nicholson (1933) and Nicholson and Bailey (1935), which have commanded attention in the field of population dynamics for a number of years, emphasized the importance of these factors in quite different ways.

Thompson assumed that the parasites have no difficulty in finding their hosts but have a constant egg supply whereas Nicholson assumed that the egg supply is virtually unlimited but that the parasites have a fixed and limited searching ability which he called their ‘area of discovery’.

The author (1959) reported on four species of Hymenoptera that had not been previously recorded as parasites of the armyworm, Pseudaletia unipuncta (Haw.). During further studies at Ottawa four more new records were obtained: Three species were primary parasites, namely, Netelia sayi (Cush.) (Ichneumonidae), Nepiera marginata (Prov.) (Ichneumonidae), and Microplitis alaskensis Ashm. (Braconidae); and one species, Catolaccus cyanoideus Burks (Pteromalidae), was a secondary parasite. N. marginata and M. alaskensis were also reared from larvae collected at Kapuskasing, Ontario.

In recent years, experimental research on feeding and nutrition of aphids has been closely associated with studies on host plant resistance or susceptibility to aphids. No satisfactory artificial feeding technique has yet been devised. Maltais (1952) and Day and Irzykiewicz (195 3) have described methods using membranes, and reviewed the literature on previous attempts to induce plant-sucking insects to feed through membranes. Recently, Maltais (1959) has offered a promising alternative method using plant cuttings in organic nutrient solutions. His new technique was developed to exploit the findings of Mittler (1957) that the natural turgor pressure of willow apparently forced phloem sieve-tube sap up the stylets of Tuberolachnus salignus (Gmelin) .

Two species that formerly were confused in the literature with Gerris rufoscutellatus Latreille are G. notabilis Drake and Hottes (1925) from western North America, and G. dissortis Drake and Harris (1930) from eastern North America. Drake and Harris (1934) concluded that Palaearctic rufoscutellatus did not occur in America.

The species described herewith as Gerris nearcticus n. sp. is similar to notabilis, dissortis and rufoscutellatus in general appearance and coloration. However, the males are readily separated from notabilis and dissortis by the prominent median keel on the first genital segment (Figs. 1, 2). Another Nearctic species with a similar median keel is G. conformis (Uhl.), but it has a very long first antennal segment, which is longer than segments two and three together. The first antennal segment of nearcticus is much shorter than segments two and three together.

The remarkable discovery that the larch sawfly, Pristiphora erichsonii (Htg.), had developed an immunity, in parts of North America, to one of its principal parasites, the ichneumon, Mesoleius tenthredinis Morl., followed Lejeune's report (6) that parasitism rarely had exceeded 5 per cent in Manitoba and Saskatchewan since 1940. Muldrew (8, 9) showed that the immunity phenomenon resulted from the formation of a phagocytic capsule around the parasite's egg. The occurrence of parasite resistance by the larch sawfly in Minnesota and Wisconsin was observed in 1952 (2, 4).

The discovery that most plant-bugs emit, when disturbed, a kind of highly penetrant and nauseous odour is not of recent origin. However, it has since then been thought that the presence of such odoriferous scents exists probably in direct adaptation to the needs and habits of their possessors. The frequent occurrence of such an odour consequently stirred the curiosity of the earlier workers to determine the exact source of this scent. No documentary account of such an attempt was, however, available until 1833 when Leon Dufour published an account of the anatomy and physiology of Hemiptera. It was thus revealed by him that the real source of the odour was actually a gland, on each side, in the ventral part of the metathorax, opening to the exterior by means of very small apertures, lying one on each side of the metasternum between the second and third pairs of legs. He worked on many hemipterous bugs, and in Cimex lectularius mentions, for the first time, in addition to the glands, a median reservoir which may be oval or round and membranous in appearance. Dufour's publication gave further impetus to the following workers, and thereafter we find persistent attempts having heen made from time to time to work out the morphology of the glands. It may be mentioned that in view of the later discoveries of the chemical nature and the odour of the secretion in various insects, the use of the term Scent-apparatus would be more precise than stink or repugnatorial scent-apparatus, employed by most of the workers up to this day, for the secretion is not repugnant in many insects; in some it has even an agreeable odour like that of ripe bananas or ether. Brindley (1930) also seems to prefer the use of the term Scent-apparatus.

The nesting biology of Hoplitis producta has been reported by several authors, as the species is a common and widely distributed bee in North America east of the Rocky Mountains. Additional records, which have been obtained in connection with trap-nest research on bees and wasps in Wisconsin, are provided to supplement the previous reports.

The nests were found in the pith at the butt ends of sumac stick trap-nests. A nest could be recognized readily because the 3 mm. plug that closed the burrow had a more solid texture and a darker color than the surrounding pith at the end of the stick. Rau (1928) found nests in tunnels of elder, sumac or rose stems but could not ascertain whether the bee excavated its own burrows or utilized burrows left by other twig-dwellers. Fischer (1955) stated that the female almost invariably excavated its own burrow. In Wisconsin, freshly cut sumac sticks were placed in the field in the spring; therefore, each of the following records represents a nest in a burrow excavated by the foundress bee.

The cinnabar moth, Hypocrita jacobaeae (L.), is the principal enemy of tansy ragwort, Senecio jacobaea L., in Europe. To determine if this moth could be safely liberated in Canada to control tansy ragwort, breeding stocks were imported as pupae from Sweden and Ireland for laboratory feeding tests. Larval feeding tests with various important economic plants before the moth was introduced to New Zealand from Britain (Cameron, 1935), to Australia from Britain (Currie and Fyfe, 1938), and to the United States from France (Parker, 1960) showed that the larvae would not survive on any of those tested. Such investigations specifically excluded certain crops from damage by the moth but did not indicate the range of plants that can be eaten. It is essential that an insect used in weed control should be highly restricted in its diet. If this restriction is related to nutrient discrimination, as described by Kennedy and Booth (1951) for Aphis fabae Scop., it would be necessary to screen many more economic plants than if it is related to “secondary” plant substances associated with a taxonomic group, as described by Fraenkel (1953). Thus, besides ad hoc tests on important plants, tests to determine the potential host spectrum of an insect are warranted before it is liberated against a weed. The plant spectrum of the cinnabar moth was determined by feeding the larvae on several genera in the tribe Senecioneae and representatives of most other tribes of Compositae that occur in Canada.

The maggot complex of Hylemya a cilicrura (Rond.) and H. liturata (Meig.) attacked flue-cured tobacco transplants in southwestern Ontario in increasing numbers from 1958 to 1960. Previously they had been of very minor importance to tobacco in this area.

Resistance was suspected near Delhi, in Norfolk County, when abnormal infestations developed in soil treated with aldrin or heptachlor. Planting-water treatments of aldrin, dieldrin, heptachlor, or lindane also failed to give appreciable control. Similar increases in house-fly populations, coincidental with decreased susceptibility to chlorinated hydrocarbon insecticides, have been noted (2).

Through the kindness of Dr. E. W. Baker of the Entomology Research Division, U.S. Department of Agriculture, and Dr. J. F. G. Clarke of the U.S. National Museum, Smithsonian Institution, I was provided with a number of mites of the family Cheyletidae. Among these were specimens of two new species representing a new genus, and a new species of Cheletominus Oudemans, formerly monotypic.

Two publications dealing with the seasonal development of species of Conophthorus have appeared in recent years. Lyons (1956) reported on a study of C. resinosae Hopk. in red pine, Pinus resinosa Ait., in Ontario, whereas Ruckes (1958) gave the details of his observations on C. radiatae Hopk. in Monterey pine, Pinus radiata D. Don, in California. Both species attack the developing cones of the host tree, although Lyons found that C. resinosae would develop in the shoots of red pine, and occasionally attacked the second-year cones of jack pine as well. The jack pine-inhabiting species, however, has been found almost exclusively in the shoots; only seven second-year cones that had been mined were collectcd during two years of investigation.

It has long been known that life events occur earlier at lower than at higher altitudes (Hopkins, 1918; Chapman, 1931; Uvarov, 1931). Treherne and Buckell (1924) refer specifically to the earlier appearance of the clear-winged grasshopper, Camnula pellucida (Scudder), near Nicola Lake, B.C., (2020 ft.), as compared with its appearance at nearby but higher places such as Douglas Lake (2600 ft.) and in the areas between Minnie Lake and Aspen Grove “where the elevation at many points exceeds 3500 feet.” These references, and the possibility of using the knowledge to help determine dates when control operations may be necessary on various ranges in any one season, suggested the need for more precise measurements of the development of this major rangeland pest at different altitudes in different years.

The genus Anoplonyx Marlatt belongs to the more generalized of the Nematinae and is clearly defined taxonomically by Ross (1937). This genus is comprised of very few known species, four in North America and four in Europe; all are associated with trees of the genus Larix. The species are similar in appearance and difficult to distinguish, especially in the adult stage.

Considerable confusion existed concerning the identification of the members of this genus in North America up until Wong (1955) published a key to separate the late feeding stages of Anoplonyx larvae found in Canada. The two species dealt with herein are apparently native to Eastern Canada and have generally been identified as one species, “Marlatt's Larch Sawfly”, A. laricis (Marlatt). Here they are identified as A. luteipes (Cresson) (= laricis Marlatt), and A. canadensis Harrington, as listed bv Ross (1951).

The genus described below appears most closely related to the genus Gronocarus Schaeffer (1927, p. 213). The description is based on a unique female collected in eastern Texas within a few miles of the Louisiana state line.

Börnerina Bramstedt is a genus of aphids that breeds only on species of Alnus L. Inclusive of the new species described herein the genus is composed of two species, of which B. depressa Bramstedt is the European representative.

Betulaphis Glendenning is a larger genus than Börnerina and as the name implies is restricted to species of Betula L. Although the genus was described in North America there have been no North American records subsequent to the original description (Glendenning, 1926). Elsewhere, the genus is known to occur in Europe, Iceland, Greenland and New Zealand. In this paper three species are recorded for North America, two of which are described as new.

In July, 1959 I reared a polyembryonic encyrtid from a species of Lithocolletis attacking Alnus crispa (Ait.) Pursh in the lake region around Ohio, Nova Scotia. It represents a species and genus new to science.

Gibberella, new genus

Type species: Gibberella scutellata Miller, new species.

In a previous paper (16) an account was given of the relative efficiency of dry deposits of Diazinon [0,0-diethyl 0-(2 isopropyl-4-methyl-6-pyrimidyl) phosphorodithioate], Trithion [0,0-diethyl S-(p-chlorophenylthiomethyl) phosphorodithioate] and Sevin[l-naphthyl N-methylcarbarnate] in preventing the reinfestation of apple trees by the apple aphid, Aphis pomi DeG. In those experiments no comparison was made of the initial effectiveness of the insecticides in killing aphids by direct contact while the spray deposits were still liquid. Instead, interest was concentrated on the relative progress of recolonization of aphid-free trees, by aphids, as a measure of the effectiveness of dried and aging deposits. In the work reported here the results of similar investigations on two further aphicides are described.

In eastern Canada larvae of the spruce budworm, Choristoneura fumiferana (Clem.), complete their development in one year, undergoing only one period of winter diapause in the second instar, whereas in certain parts of British Columbia, at high altitudes, two years are normally required for development, the larvae spending a second period of winter diapause in the fourth instar (3, 9). Among laboratory-reared eastern budworm there are a few individuals that enter a similar second diapause (7). The low incidence and somewhat irregular occurrence of this second diapause in eastern budworm, even in laboratory rearings, have hitherto made detailed studies almost impossible, but unusual storage times and treatments used recently in rearing experiments had the unexpected effect of increasing the incidence of this tvpe of behaviour to a level where experimental analysis became possible. This paper describes these larvae and their behaviour; an account of the effects of various conditions upon the incidence of second diapause will be presented later.

In the spring of 1957, Mr. K. J. Crawford, Gananoque, Ontario, took some interesting photographs of some mosquitoes that were feeding on a frog. With Mr. Crawford's kind permission, we reproduce one of these photographs (Fig. 1). This photograph was taken among the reeds of a swampy depression a few miles north of Marnlora, Ontario. As it was taken early in the season, April 26 to be exact, the mosquitoes had probably overwintered as adults. They attacked the frog fiercely, but did not bother the photographer. The mosquitoes can not be identified with certainty from the photograph, but they probably belong either to the genus Culex or the genus Culiseta. The evidence suggests that they are Culex territans Walker. This species probably overwinters in the adult stage in Ontario, is a known amphibian feeder, and is not believed to attack man (Carpenter and LaCasse, 1955).

Reports in the literature on the activities of adults of the cabbage maggot, Hylemya brassicae (Bouché), are scanty, sometimes not in agreement with one another, and usually recorded in conjunction with observations on field ecology. Now that individual insects are being used in studies of resistance in rutabagas (Swailes, 1960) a more detailed account of activities after adult emergence is available. This paper deals with the pre-oviposition, mating, and oviposition 'behaviour of the females and mating behaviour of the males.