The stabilimentum of orb web spiders is a structure for which several functions, both mechanical and defensive, have been suggested. Argiope argentata (Fabricius) builds a stabilimentum in the form of a white diagonal cross. Analysis of over 2500 webs of this species shows that the perfect cross is seldom built and nearly two thirds of the webs contain no stabilimentum at all. Experiments with wild birds as predators show that they can use stabilimentum-like models in prey location. From these data, and a review of the defensive adaptations of orb web spiders, it is argued that the A. argentata stabilimentum is not an anti-predator device. The evidence for a mechanical function is reviewed and discussed. It is suggested that the stabilimentum provides the spider with a means of making a final adjustment to the mechanical state of the web when this is necessary.

Astichus notus n. sp. reared from the birch bracket fungus Polyporus betulinus (Bulliard) Fries and woody fungus Ganoderma applanatum (Wallr.) Pat. in eastern Canada is described and illustrated and a key is included to the species of America, north of Mexico.

Larger populations of the European red mite, Panonychus ulmi (Koch), developed on artificially infested young peach trees protected by screen windbreaks than on unprotected trees. In the laboratory rather high air velocities were required to blow mites off the leaves. Agitation of leaves without contact between them had no effect on the mites. Whipping of leaves back and forth caused appreciable mortality of mites on them, and mortality was further increased when the leaves could beat together. It was concluded that wind causes considerable mortality of mites in peach orchards mostly through friction between leaves.

Experiments with rutabagas, cabbage, and cauliflower were conducted on mineral soils, mainly with pre plan tin g soil treatments of insecticides applied in bands placed about 2.5 cm below the soil surface (1.25 cm below the seed) in shallow ridges to determine the best insecticides for use in controlling the cabbage maggot. Drench or granular spot applications were also used for transplanted stem crucifers. Broadcast, surface band, and supplementary drench treatments had been tested earlier but were discarded in favor of the band-in-row treatments, mainly because of hazard to beneficial predators and parasites. Of the many materials tested, carbofuran, fensulfothion, and chlorfenvinphos have consistently given the best control throughout the growing season. Trichloronat, E.I. 47031, and mecarbam also gave good results. Thionazin and phorate gave excellent control until 1968 when applied at the exact required depth in the row with machinery; control was often erratic when these materials were applied on a field scale with hand applicators. In 1968, these two insecticides gave less effective early season control and poorer residual control than in previous years. Carbofuran, and phorate, appeared to influence the development of rhizoctonia rot lesions on the sides of the roots more than other materials in all experiments. Rot lesions were more numerous and severe on rutabagas that followed potatoes than on land that had previously been used for cereals. Root maggots in stem crucifers were controlled with a number of insecticides. Methods of application for all cruciferous crops are discussed.

A model of the seasonal development of Dioryctria amatella (Hulst.) is presented. The proposed biological model considers the various habitats where D. amatella is reported to occur. Cronartium fusiforme Hedge, and Hunt cankers and second-year cones of various pine species are indicated to be the main routes necessary to the development of Dioryctria amatella.

Rearing of Diabrotica balteata LeConte is possible throughout the year at temperatures between 10° and 30 °C. Adults feed on a very large variety of host plants. Good edibility combined with pronounced oviposition and egg viability are found in Cucurbitaceae, Leguminosae, Rosaceae, and Cruciferae. However, cases of good edibility with no oviposition are also established in several families. Optimal adult longevity lies between 17° and 24 °C and oviposition indicates two high peaks within the female life span.Temperatures below 0 °C are detrimental to all stages and those between 0° and 4 °C mainly to larval and pupal stages. No diapause is found in any stage and this explains the limited distribution within warmer regions of the Americas. Precautions not to introduce this species into other continents should be taken.

Experiments were carried out on excised leaves to determine the form of the functional response curve of the phytoseiid predators Amblyseius largoensis (Muma), A. concordis (Chant), and Typhlodromus floridanus (Muma), to increases in density of the prey, Oligonychus punicae (Hirst). The curve for each species was curvilinear to a plateau from prey densities of 1 to 70/arena, the average number killed/24 hours at the plateau being 8.5/female for A. largoensis, 5.5/female for A. concordis, and 2.0/female for T. floridanus. From prey densities of 70–300/arena, there was an accelerated rise to another plateau, in which the average number of prey killed in a 24 hour period was double that of the first plateau.Detailed analysis of A. largoensis at a density of 200 prey/arena showed the effect to be due to a stimulation–interference component, which resulted in the predator killing several prey in close succession because of increased prey contact, and because total utilization of each was minimal. During a 1 hour period, A. largoensis captured an average of 1.25 prey/predator at a prey density of 35/arena, while at a prey density of 200/arena, 3.87 prey/predator were captured. More than four times longer was spent feeding on the first prey at a density of 35 than at a density of 200 prey/arena. During the time that the predator was hungry, it was stimulated to capture and kill interfering prey that bumped into it.The functional response curve of the three predators increased in magnitude when waterproofed paper arenas were used. Four possible reasons for this increase are discussed: reduced number of prey eggs for consumption by T. floridanus; lack of webbing, which interferes with searching; increased prey activity; and dehydration of prey, affecting their relative palatability to the predator.

The number of Medetera aldrichii Wheeler adults emerging daily in 1966 and 1967 was low and irregular. Peak numbers apparently emerged 20–30 days prior to mass emergence of Dendroctonus ponderosae Hopkins although the numbers fluctuated through the mass emergence period of the beetle. Densities of emerging adults averaged less than 1 per square foot of bark and never exceeded 6.0 per square foot. Densities of the emerging flies and beetles did not appear related.Adults mated on the bark surface of trees infested with D. ponderosae; mating habits are described.Females oviposited in degenerate resin ducts in the bark surface. Two eggs per duct were the modal number. Seven or more per duct were found in less than 5% of the ducts examined.

The larvae of the following species of Dytiscidae are described and figured: Laccophilus maculosus (Germ.), L. biguttatus Kirby, Liodessus affinis (Say), Hydroporus notabilis Lec, Hygrotus punctilineatus (Fall), Hyg. tumidiventris (Fall), Hyg. punctatus (Say), Hyg. patruelis (Lec.), Hyg. impressopunctatus (Schall), Hyg. canadensis (Fall), Hyg. sellatus (Lec.), Laccornis conoideus (Lec.), Rhantus notatus Fab., Colymbetes sculptilis Harr., Agabus clavatus Lec., A. discolor Harris, A. bifarius (Kirby), A. ontarionis Fall, Graphoderus zonatus (Hoppe), Acilus semisulcatus Aubé, Hydaticus stagnalis (Fab.), Dytiscus sublimbatus Lec., D. dauricus Gebler, and D. fasciventris Say. All were collected at Delta, Man.

Cultural practices, temperature, and precipitation affect the population fluctuations of Hylobius pales (Herbst) in the piedmont of Georgia. Of the environmental factors, temperature appears to have the most decided influence on the seasonal activity of the weevils. Precipitation may cause some variation but has no effect on general population trends. Cultural practices affect the numbers of weevils collected but not the seasonal trends. Although weevils are long lived and oviposition and larval development occur almost continuously, there are two population peaks during the year.

Agathis pumila (Ratzeburg) is a host-specific univoltine solitary internal braconid parasite attacking the first- and second-instar larvae of the larch case-bearer. Descriptions and illustrations of all developmental stages are given. The adults mated in the laboratory when 1-day-old females were exposed to 5-day-old males. The reproductive system of the female is discussed. The inherent fecundity is over 300 eggs and in tests at 75°F the average number of eggs laid per female was 139.8. Average longevity is 22.0 days. The average number of hosts destroyed with the ovipositor was 15.2 per female. The incubation period of the parasite’s egg was 7 days at 77°F. The attack pattern of A. pumila is described. In finding hosts the parasite was guided by chemotaxis and vibrotaxis. Longevity of honey-fed A. pumila females, without hosts, at constant temperatures ranging from 50° to 95°F was, on the average, highest at 60°F (45.6 days) and lowest at 95°F (10.6 days). Superparasitism occurs in the field and laboratory.

The fruit-tree leaf roller, Archips argyrospilus (Walker), overwinters in the egg stage. In 1969, at Kelowna, B.C., the eggs were not affected by winter temperatures of −32 °C. Eggs began to hatch during the half-inch green stage of apple bud development, and hatching was complete by the pink bud stage. Over 50% of the young larvae fed within developing buds where they were protected from direct contact with insecticides. Adults started to emerge in early June, and peak adult activity occurred during 12 June to 19 June. Only one generation was observed during the year. The first overwintering eggs were laid in early June and egg masses were numerous by the end of June.Diazinon, azinphos-methyl, and Gardona® (2-chloro-1-(2,4,5,-trichlorophenyl) vinyl dimethyl phosphate) gave seasonal control of the fruit-tree leaf roller when applied at the pink bud stage. Phosalone did not provide satisfactory control. When diazinon or azinphos-methyl was combined with oil, control was not improved and phytotoxicity occurred to the primary leaves of McIntosh and Spartan apple trees. Gardona® sprayed trees developed damaging numbers of the McDaniel spider mite, Tetranychus mcdanieli McGregor, by mid-July. None of the other treatments affected cither phytophagous or predaccous mites.

Nymphs of the leafhopper Aphrodes bicincta (Schrank) first appeared in the field at the end of May or early June. Emergence of nymphs was protracted over a long period with second and third instar nymphs still being found when adult males were already present. Early instar nymphs were found on strawberry, Trifolium pratense L., T. hybridum L., Plantago major L., Taraxacum officinale Weber, Capsella bursa-pastoris (L.) Medic., Erigeron canadensis L., and a species of Brassica. There was only one generation per year, the winter being spent in the egg stage. Eggs deposited in plants in the field hatched when brought into the greenhouse during the winter months.In greenhouse studies, eggs were most often found oviposited on the surface of the soil or completely embedded in the petioles of leaves and in clumps of peat moss. Although eggs held at room temperature (70°–75°F) occasionally hatched, cold treatment (45°–50°F) of several weeks resulted in eggs hatching in as short a time as 14 days following their return to room temperature. There were five instars in the nymphal stage. The first four were relatively uniform in length but the fifth was at least 3 days longer than any other instar. Male insects completed the nymphal stage in 38.4 days and female insects in 41.3 days. Descriptions and measurements of the five nymphal instars and male and female adult insects are given. Adult male insects survived well for about 4 weeks and then declined rapidly. Female survival remained relatively high for at least 8 weeks. Some females have lived for up to 20 weeks. Fecundity varied with one female producing 51 offspring and others producing 1.

Winter moth hatching begins daily at approximately 0645 hours A.S.T. both in the field during the normal hatching season and in the laboratory during the winter. This diurnal pattern is not related to temperature or light and appears to be intrinsic.The seasonal rate of hatching in the spring was related to accumulated heat. Eggs first exposed to cold December temperatures then stored at 35°F (1.7 °C) until early spring, were incubated at a series of controlled temperatures. The theoretical threshold temperature of development was determined as 41°F (5 °C). Accumulated degree-days based on this threshold did not give the best estimate of the time of hatching in the field where temperatures, because they were recorded in Stevenson’s screens (meteorological cabinets), were generally lower than those at the egg sites. The best estimate was obtained by using a lower base temperature of 39°F (3.9 °C) which compensated for differences in temperature between Stevenson screens and egg sites. Mean hatch in the field occurred when accumulated degree-days reached 292.A predictive curve is presented which predicted the date of mid-hatch of the winter moth to within 1 to 2 days over a 9-year period.