Experiments conducted in cabinets in the greenhouse during the winter of 1945 showed that temperature had a marked effect on the toxicity of DDT to larvae of the diamondback moth. Plutella maculipennis (Curt.), and the greenhouse leaf tier, Phlyctaenia rubigalis (Guen.), the mortality decreasing as the temperature increased within the range of the tests. The optimum temperature for maximum kill has not yet been determined because it was not possible to run tests at all desired temperatures with the equipment available.

The first record of the occurrence in Canada of the pear fruit sawfly, Hoplocampa brevis (Klug), was made on 2 June 1964 when several larvae were collected in pear fruits near Queenston, Ontario, about one mile west of the Niagara River. The identity of the species was confirmed 26 May 1965 by Dr. H. E. Milliron, Taxonomic Section, Entomology Research Institute, Canada Department of Agriculture, Ottawa, from three adult sawflies taken in pear orchards 12–19 May 1965 and one adult that emerged in a cage 17 May 1965 from an overwintered larva.

In March, 1946, the writers reported in Scientific Agriculture (1) that benzene hexachloride showed pronounced fumigant action and that air currents as slow as 2 m.p.h. lowered its effectiveness against insects to a marked extent. The present paper deals with further experiments with benzene hexachloride and gives preliminary data on the fumigant action and effect of air currents on three other chlorinated hydrocarbons, viz., DDT, Hercules Toxicant 3956 (a chlorinated terpene) and Velsicol 1068 (a mixture of isomers with the empirical formul C10 H6 Cl8).

In connection with our studies on the Oriental fruit moth, large numbers of the insect are reared in the insectary on apples. The fruit moth eggs are placed on apples in closed containers such as No. 10 tins, and when the larvae are mature the majority of them come to the top of the containers and are placed on strips of corrugated paper in lantern globes for pupation and emergence.The remaining larvae are allowed to pupate and emerge in the rearing containers.

Large numbers of Oriental fruit moth adults were successfully tagged (500 or more counts per minute) by holding them for 24–48 hr. in cages provided with cotton wicks moistened with a water-solution of P32 at 20 microcuries per millilitre. The addition of sugar to the tagging solution did not increase its effectiveness. Approximately 80% of the total radioactivity of the tagged moths was internal due to ingested liquid and the remainder was on the surface of their bodies; 73% of the total was in and on the abdomen. The loss in radioactivity of tagged moths in 1–6 days was 2.2–4.7 times greater than the theoretical loss due to isotope decay alone. The highest rate of loss occurred during the first day, probably through excretion before the P32 was absorbed from the digestive tract. Egg laying contributed to loss of radioactivity. Though water and liquid bait removed some P32 from tagged moths this did not result in appreciable contamination of other moths trapped in the liquids.

Attempts to tag large numbers of moths (400–1000 per cage) for release and recovery experiments were only partially successful as the radioactivities attained by individual moths varied widely at different times and from cage to cage, even under the same environmental conditions. This appeared to be partly due to differences in the feeding behaviour of different batches of moths and it may have been influenced by the conditions under which they were reared.

The cage shown in the accmpanying photograph was devised by the writer as an oviposition cage for Oriental peach moths, and for this purpose proved to be very satisfactory. It has also been used with codling moths and strawberry leaf-rollers, and probably could be used with many other insects.

Feeding adults of the Oriental fruit moth, Grapholitha molesta (Busck), on a tagging solution of P32 containing 20–50 μc./ml. had no apparent effect on their longevity, mating, fecundity, and motility or on the viability of their eggs. The rate of 20–50 μc./ml. was in the range used for dispersal studies. Moths thus tagged had radioactivities of about 1500–2500 c.p.m.

Female moths fed on solutions of P32 at 100 μc./ml. showed counting rates of more than 5000 c.p.m. These females, when mated with normal males, laid approximately 33% fewer eggs than normal females. Also, the fertility of the eggs was reduced by about 25% when only the female parent was radioactive and 15% when only the male parent was radioactive to the extent of over 5000 c.p.m.

Experiments and observations on Oriental fruit moths in cages and in a peach orchard showed that both males and females may mate more than once. The maximum recorded number of matings was 7 for males and 5 for females. Mating usually occurred in the late afternoon and early evening during the daily flight and egg-laying period. Males seldom mated oftener than once in 24 hours and they transferred only one spermatophore to the female per mating. In cages, males mated approximately 1.4 times each when confined with equal numbers of females. Of the females taken in bait traps in a peach orchard, an average of 2.9% had not mated, 78.8% had mated once, 14.6% twice, and 3.7% more than twice. The mating behaviour of the Oriental fruit moth was shown to be similar to that of the codling moth.

The winter of 1933-34 was the coldest to which the oriental fruit moth has been exposed in Canada since its discovery in the Niagara peninsula in 1925, and we were naturally very interested to see how it survived. Unfortunately we have to report that it survived very well indeed, although we are glad to say its larval parasites, both native and imported, also survived.

Surveys in unsprayed apple orchards indicated that the oriental fruit moth, whose principal hosts are peach and apple, does not occur in continuing populations on apple beyond the range of commercial peach orchards in Ontario. Moths released in an apple orchard 25 mi from the nearest peach orchard did not result in an infestation after the first winter. High winter mortality due to low temperatures and the unsuitability of apple for the first generation of the moth probably are the main reasons it does not establish continuing infestation on apple alone.

It is generally considered that the smaller the particle size of insecticides applied as solids, the greater is their effectiveness. Smith and Goodhue (1) arrived at his conclusion after a review of the literature. Woodruff and Turner (4) showed that decrease in particle size of DDT wettable powders increased the toxicity of the residues against house flies, and that correspondingly better results were obtained from the residues of smallest particle size in a field test against potato leafhopper and fleabeetles. Steiner et al. (2), who have done much work on the effect of DDT particle size on codling moth control, stated that for this purpose the optimum surface mean particle diameter for DDT lies between 2.5 and 5 microns.