Platylygus luridus (Reuter) causes conelet abortion and reduces seed production in jack pine, Pinus banksiana Lamb., seed orchards in northern Wisconsin. One generation a year occurs and the insect overwinters as an egg that hatches during late May. The nymphs pass through 5 instars within 5 to 6 weeks. Adults were abundant during July and early August 1982. Eggs were laid singly within the phloem tissues of current year's shoots just below the bases of needle fascicles. The nymphs fed predominantly on the tender tissues of shoots or needles. The adults preferred to feed on ovules in the conelets, and conelet abortion resulted. About 74% of the total abortion occurred during adult feeding periods. Conditions favoring P. luridus population increases in the jack pine seed orchards included: densely planted seed orchards on high fertility sites; trees 6 to 10 years old with closed crowns or in shade; vigorously growing trees that were well watered and fertilized. Natural enemies included predators Deraeocoris albigulus, D. (possibly) laricicola, Evarcha nr. hoyi, and Misumenops asperatus.

In the summer of 1980, gypsy moth populations were monitored in 13 sparsely infested forests in southwestern Quebec; counts of living and dead larvae and pupae were made on 1,870 trees representing 28 deciduous and one coniferous species. Contrary to our null expectations, the proportionate numbers of pupae compared with larvae on the various host species were not equal. Hosts more preferred by larvae were less preferred by pupae, and vice versa. For example, pupae were disproportionately abundant on host species like Acer pensylvanicum L., Carya ovata (Mill.) K. Koch, and Juglans cinerea L. which are not generally favored larval hosts. Conversely, favored larval hosts like Quercus rubra L. and Ostrya virginiana (Mill.) K. Koch carried lower numbers of pupae than expected from the numbers of larvae feeding on them. Such differential utilization of host trees by larvae versus pupae, which can arise either from host-dependent differences in larval mortality or from late instar migration between hosts, may contribute to maintaining the broad polyphagy of gypsy moth larvae.

An energy-flow multitrophic-level model incorporating acquisition (functional response) and assimilation (metabolic pool model) functions and stochastic development is proposed and put into historical perspective. The model is general for each trophic level and for all subcomponents. Prey demand drives the functional response model, while food supply–demand determines all intrinsic rates in the model. The model is used to explore the theoretical properties of a multitrophic system comprising alfalfa, blue aphids, pea aphids, a host-specific parasitoid, and two predators (lady beetles, green lacewings). The model shows:

(1) the importance of the resource base on higher trophic level dynamics and vice versa

(2) the stability properties of different combinations of species

(3) the role of parasitoids and predators in population regulation in this system

(4) how food acquisition and respiration as functions of temperature and per capita resource interact to determine the rate of population growth

(5) that extreme caution must be used in extrapolating theoretical results to field situations.

Egg distribution by the solitary parasitoid Aphidius nigripes was studied experimentally at 14 densities of the host aphid, Macrosiphum euphorbiae. The number of hosts parasitized increased with host density, the functional response being of Holling's type II. However the average number of eggs/female was not significantly affected by host density, and consequently superparasitism increased with decreasing host density. When egg distributions were tested against random models, higher than predicted numbers of both unparasitized and superparasitized hosts were observed at all densities tested. Further analysis assuming random search suggested that female A. nigripes tend to deposit several eggs per host while experiencing a low rate of encounter with hosts. The ecological significance of this behaviour is examined.

The relationship of western spruce budworm outbreaks and population collapse to weather parameters was examined using long term weather records from two stations in the budworm outbreak area of British Columbia and outbreak patterns obtained from Forest Insect and Disease Survey records and from tree stem analyses.

Outbreaks were associated with warm dry summers in conjunction with synchrony of larval emergence and bud flush. Collapse of the last two outbreaks was clearly associated with extreme high temperatures following moth flight. Collapse of the earlier outbreaks may have been due to asynchrony between larval emergence and bud flush.

Investigation of the European pine shoot moth pheromone has revealed three components in addition to the previously identified E-9-dodecenyl acetate (E9-12:Ac): E-9-dodecenol, dodecyl acetate, and dodecanol. Inclusion of E-9-dodecenol makes lures more attractive to the moth than unmated females or E9-12:Ac alone. Dodecyl acetate had no apparent effect when added to this more attractive mixture whereas dodecanol had an inhibitory effect. Dodecyl acetate appeared to mask the inhibitory effect of dodecanol when 0.3% or more of the former component is present in the lure. Relative proportions of components are critical in comparative testing or monitoring populations of the moth.

The immature stages of Lexiphanes saponatus (Fabricius) are the first members of Nearctic Cryptocephalinae to be described as well as to be studied. The egg is coated with oblique ornamentations as in other Cryptocephalinae. The larva shows several resemblances with that of the Palearctic genus Suffrianus from which it is distinguished mainly by its large papillate frontal setae. The pupa resembles in general those of Chlamisinae but bears very distinctive projections on the seventh and ninth abdominal segments. The life cycle of L. saponatus is also very interesting. Unlike most other cryptocephaline larvae which live in the leaf litter and are unable to climb on plants, the larva of L. saponatus moves easily on its host plant (Cassandra calyculata) and mimics perfectly the plant buds, becoming almost invisible to the human eye. Although me information is incomplete, it is evident that L. saponatus overwinters in the larval stage, in the first or second instar. It is not known if the larva completes its development during the following warm season or overwinters twice as in other Cryptocephalinae.

Earlier attempts to correlate spruce budworm, Choristoneura fumiferana (Clem.), outbreaks and weather conditions were usually carried out by comparing seasonal data and spruce budworm outbreak development in broad terms: it was found that warm, dry weather favored outbreak development, while cool, wet weather retarded development. In this paper, laboratory experiments and historical data are examined to determine the effect of temperature and precipitation on second-instar larvae, just prior to and after spring emergence. Results tend to show that prolonged rain and freezing temperatures during and shortly after emergence are detrimental and may, in some cases, have a profound impact on outbreak development.

Diplolepis triforma n. sp. is described and distinguished from other members of the genus. Diagnoses are given for closely related species: D. ashmeadi (Beut.), D. inconspicuis Dailey and Campbell, D. nodulosa (Beut.), and D. verna (O.S.). Lectotypes are designated for D. ashmeadi, D. nodulosa, and D. verna. The genus Diplolepis Fourcroy is briefly reviewed. The biology and ecology of D. triforma and its gall are described. Diplolepis triforma induces a multichambered, polymorphic stem gall on Rosa acicularis and is distributed throughout central and western Canada. The form of the gall depends on the developmental condition of the host plant at the time of oviposition.

Oviposition site selection by Tenebrio molitor L. was studied in cylindrical cages 10 cm in diameter × 28 cm in height using females up to 16 days old. Oviposition site selection is not a haphazard process. The adults are surface dwellers and the females normally enter the foodstuff to oviposit. The distance travelled into the foodstuff was age-related; the females went gradually deeper until the 9th day after eclosion. Physical and chemical factors (i.e. type and quality of foodstuff) and biological factors (i.e. adult density and presence of T. molitor eggs and larvae) were assessed when oviposition sites were selected by this insect. The females attempted to avoid poor quality food when selecting oviposition sites and usually laid fewer eggs and died sooner when poor quality food was present. As adult density increased, the females went deeper to oviposit. The females also went deeper to oviposit when eggs and larvae were present, but the effects of eggs and larvae were small and there seemed to be threshold densities as far as both factors were concerned. The behavioural significance of the data is discussed.

The larvae of Rhinocyllus conicus Froel. feed within the flowerheads of Carduus nutans by tunneling through callus that appears near feeding sites, by forming chambers of callus beneath developing florets, or by tunneling within pith of the peduncle. The induction of callus by R. conicus is a gall-like response providing the larvae with additional nutriment and a shelter. Callus formation also reduces plant resources destined for developing additional flowerheads.

Two different application methods were tested using a nuclear polyhedrosis virus as a control agent at an early stage in the outbreak cycle of Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), in south central British Columbia in 1981. The virus, which often leads to the development of an epizootic late in the outbreak cycle, was propagated in whitemarked tussock moth, Orgyia leucostigma (J. E. Smith). A helicopter fitted with a boom and nozzle was used for treating four plots (total area 19.8 ha) at a dosage of 2.2 × 1011 polyhedral inclusion bodies (PIB) in an emitted volume of 11.3 L ha−1. Five to eight weeks after spraying, microscopic examination of live larvae showed that 77 to 100% were infected. In ground-spray applications of two other plots, a modified orchard-type sprayer was used to apply 2.4 × 1010 PIB in a volume of 4.5 L per tree. Microscopic diagnosis of live larvae at 8 weeks post-spray revealed 83 and 85% infection.In autumn 1981, no egg masses could be found in the plots treated earlier that year and no larvae were found on the sample trees in 1982 or 1983. The treatment was effective over a range of initial mean larval densities of 41 to 206 m−2 of foliage. At the same time, populations in nearby untreated areas increased in 1982. Little foliage protection was obtained the year of application due to the lengthy virus incubation period, but the trees recovered quickly when populations disappeared due to the virus epizootic.

A pilot black fly control program using Bacillus thuringiensis var. israelensis on a small stream system near St. John's, Newfoundland resulted in a 70% or greater population reduction of adult black flies from the previous year. The species present in the system were Prosimulium mixtum, Stegopterna mutata, Eusimulium vernum, Simulium tuberosum, S. venustum/verecundum complex, and S. vittatum. The formulation used was Teknar® flowable concentrate (Sandoz Inc.) rated at 600 ITU/mg which proved effective against the larval stages of all black fly species at a dose of 10 ppm for 1 min. The results indicated that this agent will be effective if applied at the appropriate locations and times. The 1-min dose was practical except in very cold water (0°–7 °C) where a 5-min or longer dose may be required. The unpredictable relief pattern of the northern streams resulted in a highly variable downstream carry for the B.t.i. Therefore application sites must be determined by a stream survey and not just from discharge characteristics.

Second-instar Heliothis zea (more than the 275th generation) larvae from a 16-year-old culture, were fed either green beans or artificial diet until they reached the pupal stage and then were compared to determine their relative fitness to the two diets. They proved at least as well adapted to beans as to artificial diet with regard to most parameters. Final larval weights were equal, as were pupal dry weights. Wet weights were higher in diet-fed than in bean-fed pupae. Dry food consumption was higher in diet-fed larvae than in bean-fed larvae, but the reverse was true of wet food consumption. Total food consumption by larvae was limited by food volume rather than weight or composition. The larval stage was shorter in diet-fed than in bean-fed larvae; and diet-fed larvae had better survival, higher body nitrogen, and body energy content. Oxygen consumption was lower in bean-fed than in diet-fed larvae. Efficiency of food utilization was higher for bean-fed than for diet-fed larvae both in terms of dry matter conversion and energy conversion. Nitrogen utilization efficiencies were the same for both diets.

The genus Porrhodites Kraatz is redescribed to include the Nearctic Paradeliphrum inflatum Hatch, as well as the Holarctic Porrhodites fenestralis (Zetterstedt). Orochares Kraatz is also redescribed to include Paradeliphrum (new synonymy). In addition to O. angustatus Erichson from Europe, O. japonicus Cameron from Japan and O. villiersi Jarrige from Iran, Orochares now includes two Nearctic species, Paradeliphrum tumidum Hatch from the Pacific Northwest and the new species O. suteri from Illinois and Wisconsin. Keys are provided to distinguish the North American species of each genus, and the major diagnostic characters of all included taxa are illustrated.

Adults and deutonymphs of Najadicola ingens (Koenike) are redescribed and larvae are described for the first time. In light of larval, deutonymphal and adult character states, the phylogenetic relationship of Najadicola with genera in the families Pionidae and Unionicolidae is re-evaluated and transfer of the subfamily Najadicolinae to Pionidae is proposed. Original life history information is presented to supplement existing literature. Parasitism by larval N. ingens on an adult chironomid of the genus Polypedilum is reported. The unique behavioural and morphological characteristics of members of Najadicola suggest that mussel parasitism evolved independently from a parallel adaptive sequence in the genus Unionicola.

Eggs, larvae, and pupae of eight species of Neochlamisus Karren larvae, including all Canadian species of the genus, are described, illustrated, and keys are provided for their separation. On the basis of differences in eggs, larval cases, coloration in adult stages, and in host plant, N. alni (Brown) is removed from synonymy and is considered a valid species distinct from N. bebbianae (Brown). Rearing techniques used in the present study are also described in detail.

Adults of the autumn-emerging capniid stonefiy, Mesocapnia oenone (Neave), were collected from the Bow River in the Canadian Rocky Mountains. After oviposition their eggs were incubated in the laboratory. Successful hatching occurred in the range 2°–15 °C; higher temperatures, except for a short period, were lethal. Eggs subjected to sub-zero temperatures, up to 17 days at −12 °C, also hatched successfully. Within the range 2°–15 °C there was a relationship, linear on logarithmic scales, between water temperature (T °C) and the egg incubation period (Y days), expressed by the equation: Y = 197T−0.59 (r2 = 0.99, P < 0.001). The number of degree-days required for hatching (Z degree-days) increased with increasing temperature (T °C) and also showed a relationship, linear on logarithmic scales, expressed by the equation: Z = 197T0.41 (r2 = 0.97, P < 0.001). In contrast to most other Capniidae, the winter is spent in the egg stage in M. oenone. Our data demonstrate that a combination of a low number of degree-days required for hatching at low temperatures and reduced sensitivity to higher temperatures ensures that egg hatching occurs in the spring. The characteristics of egg development in the autumn-emerging M. oenone are compared with the spring-emerging Capnia atra.

Brown larval morphs, diagnostic of Choristoneura occidentalis Freeman, and green larval morphs, diagnostic of C. retiniana (Walsingham), were found on both Douglas-fir and white fir in mixed stands in south-central Oregon. The rank proportion of brown morphs in stands was strongly correlated with the rank proportion of Douglas-fir in host species basal area component. Despite considerable overlap in most phenotypic characters, differences in phenotypic frequencies between sympatric green and brown morphs were found in larval head capsule pigmentation, thoracic shield pigmentation, pupal coloration, and adult forewing ground color. In laboratory matings, neither larval host nor larval color morph influenced the mating success, as assessed by the production of viable eggs. Crosses between females reared from brown larval morphs and males from green morphs produced a slightly lower proportion of viable eggs when compared with intramorph matings. Larval host had little effect on either the fecundity of females or the viability of their progeny. Females reared from brown larval morphs produced significantly more eggs than their green counterparts from the same stand. The occurrence of intermediates in all mixed stands and the production of families with anomalous morph frequencies indicate that these two species hybridize in nature. The lack of much structural differentiation and varying efficacy of reproductive barriers indicate that relatively little differentiation of the regulatory genome has occurred between these two species.

The field population dynamics of pea aphid (Acyrthosiphon pisum) and blue alfalfa aphid (A. kondoi) in alfalfa (Medicago sativa), as influenced by weather, competitors (Egyptian alfalfa weevil = EAW, Hypera brunneipennis), predation from coccinellids (Hippodamia convergens) and harvesting practices, are examined with a stochastic multitrophic level simulation model. The model incorporates a demand-driven functional-response model to estimate prey consumption, and a metabolic pool model to determine the rates and priorities of food allocation to respiration, growth, reproduction, and egestion.

The model results compare favorably with field data, and are used to examine the effects of removal of each of the above factors on the dynamics of the aphids. The model shows that the observed density of EAW did not affect the aphid dynamics, but did reduce the standing crop of alfalfa. The predator H. convergens had a significant effect on the population dynamics of the aphids and the plant. Harvesting greatly affected the aphid population dynamics, as well as the dynamics of plant growth and reserve accumulation. However, high temperatures mediated through species-specific respiration costs and possibly a fungal pathogen were responsible for the observed dominance of blue aphid populations in the cool parts of the year and pea aphid populations during warmer parts of the year.