The arthropod fauna associated with deteriorating crowns of alfalfa, Medicago sativa L., was studied at Ithaca, N.Y., during 1968–1969. Four decompositional stages of crowns were delimited, ranging from those of healthy, 1-year-old plants to those of dead plants. A total of 77 arthropod species, including 44 species of Diptera, were reared from the four stages of crowns. Information given for each species includes relative abundance, and associated stage of crown and number of crowns. Adults of several reared species had been collected from alfalfa foliage samples in previous years of study and were species for which the relationship to alfalfa had been obscure and which might in most insect–plant studies have been dismissed as being of chance occurrence or accidental on the plants. However, species breeding within the crowns contributed to the richness of the alfalfa fauna. Because species breeding within the microhabitat of decaying crowns were only rarely found to be associated with other morphological parts of the alfalfa plant, the crown community can be considered as a “centre of action” within the total alfalfa–arthropod community. The possible importance of considering species comprising the crown community in studies on communal stability is discussed.

None of the species of the crown community were shown to be definite primary invaders in crowns of healthy plants, although several reared species have been reported to damage living plant tissue. Many of the species probably were feeding on microorganisms and partitioning the available food resources by feeding preferentially on different classes of microorganisms. The majority of species should be classed as secondary invaders. While mechanical and winter injury probably were the main causes of initial damage to the crowns, feeding activities of the secondary-invading arthropods may have accelerated the process of crown deterioration and further opened tissues of the crown to penetration by pathogens.

Keys and illustrations are given that enable all stages to be identified of Aedes nigripes and A. impiger, normally the only two species of mosquito found in the high arctic. First-instar larvae and pupae of both species are described for the first time. Keys and descriptions are based on material from northern Ellesmere Island.

Female Heliothis virescens (F.) were irradiated with 7.5, 15.0, 22.5, or 30.0 krad of γ-rays and crossed with untreated males. Then the survival and fertility of the F1 insects from these crosses and the survival of the F2 descendants were studied. The F1 survival showed a dose-dependent reduction with increasing dose, but F2 survival was normal. Likewise, we found near-normal fertility in progeny from irradiated females, regardless of dose.

Two species of Rheumaptera occur in North America: R. hastata (Linnaeus) and R. subhastata (Nolcken). All stages of the two species are described and illustrated. Keys are given to separate the species in the adult and mature larval stages. Additional information on distribution (supplemented by maps), habits, and hosts is provided.

Bessa harveyi (Townsend) is a common parasite of the larch sawfly, Pristiphora erichsonii (Hartig), in southeastern Manitoba but it is ineffective in preventing or terminating outbreaks of its host. Bivoltinism acts as a mortality factor in B. harveyi populations because bivoltine individuals do not contribute progeny to the next generation. Heavy mortality due to bivoltinism occurs when the parasite eggs are laid under long-day conditions and the summer is warm and prolonged. Regression analyses show that most of the variation in the incidence of bivoltinism between years and between dates within years can be described by equations involving the incidence of bivoltinism in the previous year, photoperiod, and temperature. The importance of a genetic factor in determining the incidence of bivoltinism was indicated by a strong negative correlation between the incidences in consecutive years. Photoperiod and temperature during development were positively correlated with incidence. The persistence of bivoltinism in Manitoba is postulated to be related to variability in weather and host development plus developmental advantages associated with the bivoltine phenotype.

The egg, first larval instar, last larval instar, and pupa of Sialis cornuta Ross are described and illustrated.

A new genus, Dianemobius, is diagnosed, with Eneoptera fascipes Walker, 1869, as type-species, since this species is not congeneric with Pteronemobius concolor (Walker), the type-species (a senior synonym of the originally designated Nemobius tartarus Saussure) of Pteronemobius. Notes on morphology and cytology which indicate the heterogeneity of Pteronemobius are included.

The spider fauna of alfalfa was studied at Ithaca, N.Y., in three experimental plots and in nearby fields during 1966–69. As part of an overall study of the arthropod fauna of alfalfa, the spider populations in the study plots were recorded weekly during visual examination of the terminal 6 in. of five stems for 100 plants in each of the plots. Additional information was obtained from sweep-net and pitfall trap collections in the study plots and from sweeping several commercial plantings. The spider fauna of alfalfa was found to consist of 78 species, 10 of which were collected only from the ground layer. Tetragnatha laboriosa Hentz and Dictyna volucripes Keyserling were the most abundant species found in the weekly samples. Notes on the seasonal occurrence, location on the plants, and feeding habits are given for the common species.

Honey inhibits esterolytic and proteolytic activity of trypsin from Aedes aegypti, Culex pipiens quinquefasciatus, and cattle. The inhibitor is heat stable and only a portion of the inhibition capacity is lost from the honey by dialysis. Glucose, fructose, and sucrose have no effect upon trypsin but ascorbic acid and riboflavin are inhibitory while gluconic acid is an activator. Nectar from lilies but not from honeysuckles inhibits C. pipiens quinquefasciatus trypsin.

A trap to detect beetles in stored grain is described and compared with earlier versions and other sampling devices. Being escape-proof the trap can be left in grain for long periods thus increasing its reliability. It is strongly constructed of rust-proof materials to withstand field use. It is economical, light, compact, and simple to use in the field or laboratory. Preliminary trials show that it is highly effective as an insect detector and trap.

Laboratory nests of Formica sublucida Wheeler, F. sanguinea subnuda Emery, and F. fossaceps Buren were used to determine the foraging activity of these three species by accurate hourly measurements, day and night, for three summer seasons. Soil temperature in each nest was thermostatically controlled and maintained at 50°, 60°, and 70°F.

The species foraged day and night, with a peak of activity in late morning and mid-afternoon. Increasing soil temperature resulted in an increase in foraging; barometric pressure and relative humidity had no apparent effect.

The seed maggot complex, Hylemya (Delia) platura Meig. and H. (Delia) liturata Meig., is shown to be a primary pest of radish. In laboratory experiments larvae of this species complex attacked radishes and developed into pupae whether or not the plants were already damaged by the cabbage maggot, H. brassicae Bouché.

The effects of various levels of infestation of the corn leaf aphid, Rhopalosiphum maidis (Fitch), on yield of field corn were examined from 1965 to 1970 inclusive when all plants whose yield might have been influenced by factors other than aphid feeding were excluded from the data. A possible relationship between moisture stress in plants and degree of aphid injury was also investigated.

A light infestation (maximum of 400 aphids on the tassel) caused average yield reductions up to 8.3% when plants were under moisture stress, but nil to negligible losses when moisture was adequate. Moderate infestations (many hundreds of aphids on part of the tassel) produced average losses up to 34.8% under drought conditions and up to 11.8% when moisture was abundant. Severe infestations (many hundreds of aphids on most of the tassel) caused average yield reductions ranging from 43.2 to 91.8% when plants were under water stress and up to 58.9% even with abundant moisture. Very severely infested plants (many hundreds on all of the tassel and whorl leaves) were usually barren or had ears with just a few kernels regardless of moisture conditions.

Most injury from aphid feeding appeared to occur before and during pollination. No particular combination of temperature and rainfall favored aphid buildup.

Induction of supernumerary larval instars in the spruce budworm, Choristoneura fumiferana Clemens, by applying ZR-515, a potent juvenile hormone analogue, is explained in terms of larval differentiation. Application to the early sixth instar where structures are relatively indeterminate results in the formation of a supernumerary larval instar, whereas treatment of the late-larva wherein many structures are committed to differentiate towards the pupa, results in a larval–pupal mosaic.

The life history of Epinotia aceriella (Clemens) is discussed and the life stages described. Information is presented on feeding behavior, distribution, hosts, and natural enemies. Control recommendations are made.

Changes were recorded in dry matter content and in the metabolism of lipids and nitrogen during the postembryonic development of Pseudaletia unipuncta (Haw.) on corn. The study revealed that 22 to 24% of the lipids were used during moulting and pupal–adult transformation and that nitrogen was not lost during such periods. The coefficient of apparent utilization of nitrogen remained more or less constant; however, that of lipids decreased with larval development. No significant difference was evident in the relationship between lipid consumption and weight gain, and nitrogen consumption and weight gain during larval development. A direct linear relationship was obtained between nitrogen and lipid utilization during all instars. In terms of heterauxesis, the accumulation of lipids during larval development was opposed to that of nitrogen.

A study of sampling variation in the white grubs Phyllophaga fusca Froelick and P. anxia LeConte in a permanent meadow showed that inter-plot differences occurred in 70% of the samples. Block differences were rarely significant. For all stages, the most appropriate sample unit was a 1 ft cube of soil and sod. The number of samples required was inversely proportional to population density; this relationship was graphed for three levels of sampling precision.

Adults of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), were placed on the surface of grain in plastic cylinders. After 48 hours records were taken of the number passing through a perforated brass screen at the bottom of the cylinders and into petri dishes containing wheat inoculated with different species of fungi. More adults were found in dishes of spoiled grain containing a mixture of fungi than in empty (control) dishes or dishes with water. The largest number were found in dishes containing Penicillium corymbiferum and the second largest number in dishes with Scopulariopsis brevicaulis, Fusarium sp., and spoiled grain. The least number occurred in dishes with Streptomyces sp., uninfected wet grain, or dry grain. The response to fungi is probably induced by olfactory stimuli from volatile compounds in the fungi or by-products of fungi.

High correlations between food consumption and excretion in terms of dry matter, calories, lipids, and nitrogen were obtained during the larval stages of Pseudaletia unipuncta (Haw.). The regression coefficients for this relationship in terms of dry matter did not differ significantly from those of calories; this leads to the hypothesis that the ratio of food consumption and excretion in terms of dry matter in a particular larval instar provides an estimate of caloric intake.

Diagnostic characters of Euxoa albipennis (Grt.), E. lillooet McD., E. declarata (Wlk.), and E. campestris (Grt.) are discussed. Euxoa rockburnei and E. declarata californica are described as new species and new subspecies, respectively. Adults and genitalia of the constituents of the series are illustrated and a key to species is presented.