Radionuclides may be used as ecological tracers to study trophic–level relationships. To use cesium-137 to investigate the role of the giant water bug, Lethocerus americanus (Leidy), in the food-web of a small pond, it was necessary to measure the elimination rate of the nuclide. The experimental determination of the elimination rate of cesium-137 in fourth instar and adult water bugs, and the calculation of the fraction of ingested food assimilated is described.

The punctigera group of the genus Euxoa is defined on the basis of genitalic characters. Species included in this group are Euxoa punctigera (Wlk.), E. spumata McD., E. stigmatalis (Sm.), E. aurantiaca n. sp., and E. cana n. sp. Adults and genitalia of the species are illustrated and a key to species is included.

Choristoneura houstonana (Grote) lays eggs singly in July. Egg development ranged from 8 to 11 days, with the majority hatching 10 days after oviposition.

Larvae are solitary, and mine during early instars but later instars feed externally on leaves in shelters made by webbing foliage together. There is one generation each year and overwintering occurs in a hibernaculum, in mined leaves. Field-collected head-capsule width frequencies indicated nine larval instars. Rearing larvae on seedling junipers indoors indicated a range of 8–11 instars.

Pupation occurs during June and July in the shelter where the larva feeds. The pupal stage lasted about 10 days at a constant temperature of 80°F.

The identity of Scotogramma oregonica Grote has always been a matter of some doubt to taxonomists. Smith gave his idea of the species in a paper entitled “Notes on Mamestra trifolii Rott. and Its Allies” (1910, Ent. News, XXI, 357); Wolley-Dod (1913, Can. Ent., XLV, 31) surmises a mixture of species in Grote's type lot of material and states that the male type in the Neumoegen Collection at Brooklyn (now incorporated in the U. S. Natioonal Museum) is the same as Smith's morana (op. cit., p. 361) ; following Dod morana was made a variety of oregonica in the 1917 Barnes and McDunnough Check List.

Hybridization has been studied in mosquitoes ever since caged colonies began to be maintained. Aedes particularly of the subgenus Stegomyia have been crossed variously at different times and by different observers. Anopheles species, particularly some of the subgenus Anopheles, have been hybridized with varying results. However techniques for inducing copulation developed in this laboratory (McDaniel and Horsfall, 1957) and used on Culiseta, Psorophora and many Aedes make possible combinations unlikely by chance in cages. Cage adaptation is not a prerequisite for success neither are precopulatory stimuli.

The familiar species Pycnarmon jaguaralis (Guenée) ranges from the Himalayas to the Solomons and Queensland with comparatively little variation. Specimens from Buru, Obi, Luzon, Amboina and Waigeu seem hardly different from those from the Himalayas.

Head capsule widths were measured on 962 larvae of Rhyacionia rigidana (Fernald). Five instars were detected using multimodal analysis, and normal distributions of head widths for each instar are given. Regression using an exponential growth model was used to generate mean head widths according to Dyar's rule. These widths did not differ significantly from observed widths.

The streams and lakes of western Montana offer a variety of habitats for species of aquatic insects but heretofore extensive collection and study of these forms has not been undertaken. During the past two years collections of both nymphs and adults have been made on several streams. The Plecoptera in these collections include the undescribed nymphs of Nemoura cinctipes Banks and several species which have not been reported for Montana.

Aphids of the species herein described as new can be readily distinguished from all other species in the genus Cinara by the unusual length of the unguis. The feeding site is also characteristic; this is the only species in the genus known to feed on the roots of Pinus banksiana.

The species was first collected in 1956 at Lac La Ronge, Saskatchewan, by B. B. McLeod, of the Winnipeg Laboratory. In 1957 it was found by the authors at Cedar Lake, thirty miles north of Vermilion Bay, Ontario, where observations on the life history of the species were carried out.

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 following notes were presented to the Entomological Society of Washington, May 1, 1980, under the title of “Some insects affecting certain forest trees.” They are herewith somewhat revised and sifted for publication, since the matter which follows is of some value.

Since the issue of the Check List of N. A. Coleoptera by the late Mr. G. R. crotch, I have been asked by several persons interested in that branch of science, if I would advise them to change the labels in their collections in accordance with the nomenclature of several familiar genera as therein set forth. To all such applicants I have answered, that such changes are not expedient, unless they are fully, convinced of the propriety of admitting them. For my part, I considered them quite unnecessary, and still further, contrarry to the code of laws of nomenclature under which I supposed we were acting.

Prof. Smith says that he uses the name Xylina in preference to Lithophane, because both are catalogue names and Xylina has priority, since the Verzeichniss was not published until 1818 at least. My argument is, that Ochsenheimer took the name Xylena from Hübner's which is not a Lithophane, but a Hadena.

Euxoa vernalis, allied to Euxoa olivia (Morrison) and Euxoa septentrionalis (Walker), is described from south-western United States and from Mexico. Adults and genitalia of the three species are illustrated.