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Larvae of Hypoderma bovis (L.) and H. lineatum (De Vill.) when incubated with the substrate acetylthiocholine iodide showed the presence of cholinesterase throughout the central nervous system and sense organs, in gonads, oenocytes, Malpighian tubes, anlagen of adult structures, part of the posterior midintestine, and at the junctions of the muscles of the body wall. Incubation with the substrate 5-bromoindoxyl acetate showed all the aforementioned and in addition demonstrated the presence of aliesterase (organophosphorus-sensitive esterase) in the cell cytoplasm of all the midintestinal epithelium, the ring gland, tracheal epithelium, salivary duct epithelium, and in the perineurium of the nerve sheath. Aromesterase (organophosphorus-resistant esterase) was particularly abundant in the epithelium of the midintestine. Lipase was prominent in the lipid droplets of the fat body cells and in similar droplets in the haemocytes.

When the larvae or their tissues, prior to incubation with the substrates, were treated with any one of the three organophosphorus insecticides coumaphos (Co-Ral), trichlorfon (Neguvon, Dipterex), or Ruelene, the cholinesterase was inhibited and so was much of the aliesterase, but not the aromesterase or lipase. Fixation of the larval tissues in formalin did not result in loss of enzyme activity, but on the other hand was not necessary for good histochemical demonstration of the enzymes.

It is concluded that these insecticides by their anticholinesterase action kill the first-instar cattle grubs before the latter can migrate to the lumbar region of the bovine host.

The genera Leptohyphes Eaton and Tricorythodes Ulmer are confined to the New World, and the Nearctic limits of Leptohyphes has been extended from Texas to Maryland and Utah. Useful nymphal characters are presented for both genera, and descriptions and figures are included for 22 new species of Leptohyphes Eaton, and 7 new species of Tricorythodes Ulmer.

Like all other Tryphoninae, the European species of Exenterus have eggs that are attached to the host by a stalk inserted into the host integument. Their eggs present an interesting series of evolutionary steps from the typical tryphonine condition in which the egg has a small single stalk with a knob-like anchor to an extremely specialized condition in which the stalk is doubled and its two parts migrate to opposite ends of the egg; the anchoring part of the stalk is concurrently enlarged until it half encloses the egg and functions as an extremely efficient organ of attachment to the host cuticle. In dry periods the simple type of stalk becomes brittle and easily broken, resulting in the death of the parasite. The specialized eggs with protected stalks are not subject to such hazards; thus species with specialized eggs can succeed in drier climates and can better survive droughty seasons. Correlated with these specializations is an increase in range of species, and greater abundance of individuals. The success of the European species introduced into North America for biological control has been roughly proportional to the amount of specialization in the egg structure. Little is known of the life histories of the American species of Exenterus but the few facts available do not appear to contradict the type of correlation exhibited by the European species.

None of the saturated C6–C14 fatty acids fed free as components of a chemically-defined diet to larvae of Pseudosarcophaga affinis Auct. nec Fallén (Diptera: Sarcophagidae) improved the rate of growth and development, but several were toxic. In descending order of toxicity, the fatty acids were capric (C10), caprylic (C8), caproic (C6), and lauric (C12); myristic (C14) had no apparent effect. The ED50 was 0.00025 M of capric acid, 0.054 M of caprytic acid, and 0.155 M of caproic acid, respectively. Even at 2.5% of the diet lauric acid was not very toxic. The effects of fatty acids on P. afjinis are similar to those on other insects, though the order and degree of toxicity varied in some cases. Of course, certain fatty acids were widely used as insecticides: their activities varied with molecular configuration and physical–chemical properties. Present insight, however, is that certain fatty acids when eaten may be beneficial to some species and harmless or injurious to others. This suggests that perhaps fatty acids may be useful selective insecticides or substitutes for more dangerous chemicals.

The following four new species of Udea are described: U. decoripennis, Chile; U. soratalis, Bolivia; U. coranialis, Bolivia; U. punoalis, Peru.

Mating in Coleophora laricella (Hbn.) took place 1 or 2 days after emergence and was stimulated by decreasing light intensity ranging from 3000 ft-c to 200 ft-c within 2 hours. The female is pro-ovigenic, with peak opposition during the first week. Optimum temperature for egg laying was 70 to 80°F; the average number of eggs deposited was about 66; average longevity of female adults was about 10 days at room temperature, but considerably longer at lower temperatures. A few eggs were laid at 50° and 95°F. Incubation period of the eggs was 12 days at 80° to 85°F and 40 days at 55°F. Hatching of eggs did not occur above 85°F or below 55 °F.

An assay procedure for estimating the dosage–response relationship of early instar larvae of the onion maggot, Hylemya antiqua (Meigen), to insecticides is reported. The method gave reproducible results for diazinon on several test dates. The assay showed that maggots from strains collected at East St. Paul and Portage La Prairie, Man., tolerated 50 to 108 times as much heptachlor as a susceptible strain from Chatham, Ont. Previously, adults from the Manitoba strains had been shown to be highly tolerant to heptachlor. The potencies of Bayer 37289 and Bayer 25141 relative to diazinon were 0.5 and 0.1, respectively, for a heptachlor-tolerant strain. For NIA 10242 and Nemacide, equivalent values were 0.9 and 0.2 for this strain and 1.0 and 0.2 for the susceptible Chatham strain. The slight differences in the tolerance to these insecticides, shown for the two strains of larvae, were not associated with their tolerance to heptachlor.

Results of the analyses for digestive enzymes in the glands and midguts of five species of ants showed that invertase is usually secreted by the maxillary glands, amylase by the salivary glands, and protease and lipase by the midgut. Lipase was found in the post-pharyngeal glands but observations indicate that it is not associated with the digestion of ingested food. Differences in the activity of the enzymes in different species tended to reflect the feeding habits of the ants.

A study was made of the poplar-and-willow borer, Sternochetus (= Cryptorhynchus) lapathi (L.) (Coleoptera: Curculionidae), in British Columbia between 1959 and 1964. The borer occurred principally south of 52 degrees north latitude. Willows were the preferred hosts. Ornamentals, hybrids in commercial plantings, and natural growing trees were attacked. The life cycle of the insect on southern Vancouver Island lasted up to 3 years; overwintering took place in early instar and adult stages. Eggs were laid in the bark; larvae mined first in the bark and then in the wood, where pupation took place. Few parasites and predators were found. DDT, dieldrin, and BHC killed adults; lindane (0.5% water emulsion), applied in the spring, caused larval mortality up to 96%.

This paper contains six annotated keys to the larval behavior of 28 species of Lepidoptera that mine the leaves of Picea spp., Abies spp., Tsuga canadensis (L.), Larix spp., Juniperus spp, and Thuja occidentalis L.

An illustrated key to the last-instar larval cephalic structures of parasites reared from larvae of Spilonota ocellana (D. & S.), notes on habits of the parasites, and a description of their cocoons and pupae are given. Rearing techniques are described. The parasites reared are Gelis tenellus (Say), Hyposoter sp., Meteorus argyrotaeniae Johansen, Phanerotoma recurvariae Cush., Apanteles sp., Agathis dimidiator (Nees.), Euderus cushmani Cwfd., and Sympiesis bimaculatipennis (Grlt.).

The first record of Frumenta nundinella (Zeller) in Canada is reported, with notes on development in the only known host, Solanum carolinense L.

Surveys in unsprayed orchards showed that the wild flowers that are food sources for adult parasites influence the extent to which host Lepidoptera are parasitized. Proportionately about 18 times as many tent caterpillar pupae were parasitized in orchards with rich undergrowths of wild flowers as in orchards with poor floral undergrowths. The corresponding figures for tent caterpillar egg parasitisms were about 4 to 1, and for codling moth larvae about 5 to 1. Orchards with average undergrowths of wild flowers produced intermediate figures.