Spruce budworm infested balsam fir trees were aerially sprayed with Bacillus thuringiensis – chitinase combinations at the rate of 4 Billion International Units of B.t. and 18 mg of enzyme in 0.5 gal/acre. Larvae were peak third instar at spray time. Deposit rates ranged from 1.07 to 3.26 BIU/acre. Efficacy of the treatments was assessed in the year of treatment and carry-over effects were assessed 1 year later.

Results in the year of treatment indicated that: (1) Residual activity of B. thuringiensis was drastically reduced after 15 days’ exposure to weathering. (2) Larval mortality alone is not a suitable criterion of efficacy. (3) Dipel and Dipel + chitinase (but not Thuricide 16B or Thuricide + chitinase) were highly effective in reducing budworm densities. (4) Thuricide + chitinase treatment resulted in significant foliage protection. The treatments inhibited feeding in the following order of efficiency: Thuricide + chitinase > Dipel + chitinase > Dipel alone > chitinase alone > Thuricide alone. (5) There was no direct relationship between larval mortality and foliage protection in any of the treatments, likely due to delayed mortality effects. (6) No direct relationship exists between viable spore deposits and deposit of active ingredient (IUs). (7) B.t. treatments retarded development of the spruce budworm and reduced pupal weights, oviposition rates, and egg viability.

Assessment of the plots 1 year after spray showed that the treatments apparently gave no long term protection from defoliation, but this was likely due in part to mass invasion of the test plots by moths from immediately surrounding untreated areas.

As part of the biological control of Canada thistle, Cirsium arvense (L.) Scop., in Canada, a survey of the insect fauna showed 80 identified or apparent phytophagous species representing 24 families and seven orders and 47 species of visitors, insect parasites, and predators representing 28 families and six orders. Thirty-eight per cent of the phytophagous insects attack economic plants. Three species, Altica carduorum, Ceutorhynchus litura, and Urophora cardui, are specific to C. arvense and were introduced as control agents.

Seasonal occurrence of three important grasshopper species (Melanoplus sanguinipes (Fabr.), M. bivittatus (Say), and Camnula pellucida (Scudder)) is estimated. The predictions are based on the amount of embryonic development occurring in fall after oviposition and the rate of egg and nymphal development in spring. Embryonic development is calculated from heat units accumulated above 50°F (10 °C) from daily maximum and minimum temperatures from 1 August to 30 September. Egg and nymphal development during spring can be monitored by accumulating heat above 50°F (10 °C) using daily maximum and minimum temperatures from 1 April.

The number of heat units required by each life stage is provided for comparison with current heat accumulations. The average date of occurrence from hatch to adults is provided based on 17 years of weather data from seven Saskatchewan weather stations.

Studies were carried out to investigate the growth response of normal and defoliated spring wheat. Plant growth is expressed by the von Bertalanffy (1957) growth equation modified to allow for declining growth potential with age. Grasshopper damage was assessed by comparison with artificial defoliation and results indicated a simple linear relationship between grasshopper food consumption and defoliation damage. On the basis of this relationship it indicated that grasshoppers feeding on wheat waste 6.2 times as much foliage as they actually consume. Damage to foliage is translated into an effect on grain yield by an allometric relationship between total plant weight and yield. A simulation model indicating the time course of plant biomass provides realistic estimates except in the case of acute defoliation.

Continuous trapping on the bark surface of trees infested with Dendroctonus brevicomis LeConte was carried out during six beetle generations from June 1969 to November 1971, at the University of California’s Blodgett Forest Research Station in the central Sierra Nevada mountains. Significant linear correlation was found between the density of D. brevicomis trapped on the surface of infested trees and the initial within-tree beetle densities. In the first beetle generation, mass arrival was rapid and intense (averaging 1167 beetles per 2.7 sq. dm of trapping surface on each tree, during a mean of 8.8 days). The arrival patterns during this generation were quite consistent between trees. During the second generation, mass arrival was prolonged over a mean of 19.4 days and fewer beetles were trapped ( per 2.7 dm2 of trapping area per tree). The patterns of arrival were more variable during this second generation. In generation 1, with the exception of one tree, the beetles were distributed equally at the three trapping heights (4.5, 7.5, and 10.5 m). In generation 2 they were more abundant on the traps at the lower portions of the tree.

Continuous trapping on the bark surface of Dendroctonus brevicomis LeConte infested trees in the central Sierra Nevada mountains was undertaken with the objective of determining the spatial and temporal arrival patterns of the natural enemies and other insect associates of the western pine beetle. Over 100 species of D. brevicomis associates were collected and patterns of arrival were described for many of these. The main bark beetle predators were trapped during D. brevicomis mass arrival and shortly thereafter. Enoclerus lecontei, Temnochila chlorodia, and Aulonium longum, all predaceous beetles on D. brevicomis adults and larvae, were among the first species to arrive, as was Medetera aldrichii (Diptera), a larval predator. The bark beetle parasites Roptrocerus xylophagorum and Dinotiscus (=Cecidostiba) burkei (Hymenoptera) were well synchronized with the beetles’ life cycle as they arrived late in the beetles’ larval stages when suitable hosts were available.

Approximately twice as many associates were trapped in the first (spring) beetle generation as in the second (fall). Differences between species with regard to height distribution were common, and these often varied with seasonal beetle generation.

Calculations of changes in species diversity through time, of the associate complex trapped at the bark surface, were made for both the first and second beetle generation. Linear correlation analysis indicated a highly significant increase in species diversity occurred from the time of the beetles’ mass arrival until brood emergence. This increase may correspond to an increase in diversity of the structure of the subcortical community, as more insect species arrived and progressively modified the habitat of the newly killed tree.

Onymacris rugatipennis is one of several diurnal adesmiine tenebrionid beetles living in various habitats near Gobabeb in the Namib Desert, South West Africa.

Late in the active part of the female daily cycle and before they dig into the ground, females are often persistently followed by one or more males. Intruding male challenges to followers are commonplace. Following occurs during the latter phase of the morning and especially during the afternoon activity cycle. Early in these activity cycles the principle male activity is feeding. Males emerge in the morning earlier than females, and late in their activity period most males are engaged in following or attempts to dislodge other followers. Of the five diurnal adesmiine species living near Gobabeb, only the males of O. rugatipennis fight with one another and defend space. Their space is maintained above the site where a female has dug into the ground at midday or in the evening. Defense involves exclusion of other males from the immediate vicinity of the female. Alien males are immediately evicted, but on some occasions there are serious challenges. Pairs of males may engage in vigorous wrestling matches involving head butting, shoving, throwing, biting, and kicking. Evenly matched individuals may wrestle for over 30 min and for more than 20 falls. The winner of such encounters remains over the buried female. The last individual to hold the space in the evening may mate with the resident female. The observed behavior is not territorial in the sense that there are no mutually recognized frontiers. There is, however, exclusive use of space and aggressive defense of that space.

Social order is re-established daily. There are no persistent inter-individual bonds between males and females. Males may return to the general area but not the exact place where they held space the previous day. Many individuals move long distances from the place where they were active on the preceding day.

Larger males tend to win wrestling matches. However, males are on the average smaller than females. Since larval males live in the habitats occupied by females, adult male body size is apparently not limited by larval energy limits. Hence we conclude that small adult male body size conveys advantages which may outweigh the disadvantage in wrestling matches. Some of the possible selection relationships countering large male size are discussed.

Females reject most mating attempts by males when they are active on the surface. They exercise no choice in mate selection following burrowing. Hence the mating system results in mating by the most persistent male followers and aggressive individuals able to hold the space above the place where the female burrows into the ground.

Laboratory tests showed that the mating frequency of males of Neodiprion sertifer (Geoff.) averaged 4.28 and varied from 0 to 11. A few adults of both sexes did not mate, despite repeated opportunities. As many virgin as mated females oviposited, but virgins laid 19% fewer eggs. Progeny sex ratios were independent of the number of previous matings by the parental male, but apparently were inversely related to the male’s mating ability and may have been determined paternally.

Laboratory and field tests revealed the possibility of infecting larvae of Hyphantria cunea Drury with the nuclearpolyhedrosis virus of Thymelicus lineola (Ochs.). H. cunea is highly susceptible to the action of this virus, particularly the second instar larvae where mortality reached 100%. Virus infected larvae of H. cunea showed the same symptoms of infection as those observed on the original host, T. lineola. Several problems still have to be elucidated, namely to determine whether T. lineola or H. cunea is the primary host as both species often live in the same phytocenosis.

Mating studies with M. sanguinipes (Fabr.) indicated that egg hatchability and percentage of males among the hatchlings decreased as copulatory period decreased; this was probably caused by depletion of viable sperm in the female resulting from inadequate sexual contact with the male.