A technique is described for rearing successive generations of the insect in numbers from 200 to 40,000 continuously without diapause. All components of the diet are commercially available and the principal ingredients are of plant origin. Survival at four stages of development is given and the causes of mortality are discussed. The per cent survival of insects from instar III to pupation times the percentage of perfect female pupae obtained at harvest gives a factor considered to be the best measure of the worth of an artificial diet. The variability of these statistics is shown by frequency distributions obtained in 50 independent tests of the diet. Overall survival of 84% times 73% perfect females gave a diet worth factor of 61. An analysis of rearing costs is presented. Although 15 continuous generations have been reared, egg production of the highly selected strain has not deteriorated.

The attractiveness of colored spheres was compared in the field for several tabanid species. Black and red spheres were highly attractive to all the species. Tabanus illotus was attracted nearly equally to black, gray, and white silhouettes. The attractiveness of gray and white spheres for the other species decreased rapidly with increasing reflectance. Green and yellow spheres were unattractive for all species. Two-dimensional black silhouettes attracted only a small number of tabanids. Three-dimensional black silhouettes with plane surfaces attracted larger numbers of flies. Glossy black silhouettes with convex curvature in the vertical plane were much more attractive than other silhouettes. Interpretations of these results are presented.

The Manitoba Fly Trap is illustrated and described and its uses in behaviour studies, surveys, insect control and perhaps population studies are enumerated. Its advantages over other traps for diurnal biting flies are discussed. Zusammenfassung DIE ORIENTIERUNG DER BREMSEN (TABANIDAE, DIPTERA). III. DIE VERWENDUNG DER MANITOBA‐FLIEGENFALLE BEI LANDE‐UNTERSUCHUNGEN AN BREMSEN Die “Manitoba”‐Fliegenfalle wird abgebildet und beschrieben. Ihre Verwendungsmöglichkeiten bei der Verhaltensforschung, Sammlung und Bekämpfung von Insekten und vielleicht bei Massenwechselstudien werden aufgezählt und ihre Vorteile vor anderen Fallen für den Fang diurnaler Stechfliegen diskutiert.

The Canadian population of Delia radicum is more cold hardy than the English population in that the supercooling point is slightly lower and overwintering pupae are less sensitive to lower temperatures and longer exposure times. However, the Canadian population is slightly less cold hardy at higher temperatures within the cold injury zone. Female D. radicum were more susceptible to cold-induced mortality than males among the Canadian population, but this sex difference was not significant in the English population. The proportion of malformed adults and the rate of postdiapause development were not related to cold injury in either population. The bounds of the cold injury zone for species or populations of freezing susceptible, diapausing insects plus the sensitivity of the species to cold injury within this zone can provide an ecologically sound method of describing cold hardiness. Sensitivity, measured by the slope of a regression describing the relationship between survival and the duration of exposure at a low temperature, can also be used to calculate the rate at which cold injury occurs at any temperature within the cold injury zone. This slope may reflect the overwintering conditions of a species or population because Canadian populations of both D. radicum and Mamestra configurata (Noctuidae) have similar coefficients, but these are very different from the coefficient of the English population of D. radicum. The supercooling point did not provide a useful indication of the susceptibility of these cold-hardy diapausing insects to cold injury.

Feeding tests in which various components were omitted individually from a chemically defined diet for adults of the parasitoid Exeristes comstockii (Cress.) (Hymenoptera: Ichneumonidae) showed that amino acids, salts, and vitamins were needed for maximal egg production and maximum numbers of eggs contained in ovaries. Omission of fatty acids, ribonucleic acid and cholesterol had no effect. Only omission of vitamins lowered egg hatch. Tests showed that the ovaries could recover from vitamin starvation.