New species of Ablautus Loew described are arnaudi from Baja California and California, basini from California and Nevada, colei from Washington and Oregon, and coachellus, linsleyi and schlingeri from California; females of californicus and vanduzeei are described; and a key to the species is given. New species of Omniablautus Pritchard described are nigripes and tolandi from California; Ablautus rubens Coquillet and A. nigronotum Wilcox are transferred to Omniablautus; and a key to the species is given.

A quantitative method is described for measuring the nuisance caused by non-biting aquatic insects (Chironomidae, Trichoptera, Ephemeroptera) in the absence of a human observer. Threshold nuisance densities referring to different human occupations are given; and application of the method is discussed.

Hydropsyche corbeti, Cheumatopsyche montrealensis, and Protoptila expositionis n. spp. are described from Montreal, Quebec. A total of 93 forms are listed, three of which are represented only by females and cannot be identified to species. An additional species is recorded only from Chambly, Quebec. Thirty-four genera and 13 families are represented in the list.

Epinotia nanana (Tr.) has become increasingly important in recent years in Quebec as it has caused severe defoliation of ornamental spruce trees in the Berthierville area, Quebec. The insect has a one-year life cycle and overwinters in the larval stage, mainly in the fifth instar, in a mined needle. Damage is most noticeable in the spring. Fairly heavy mortality, probably due to unfavourable climatic conditions, occurs among overwintering larvae. The amount of control exerted by parasites is always low.

Paraprosalpia dytisci new species is described from a larva, puparia, and adults reared from a dead larva of Dytiscus fasciventris Say, collected in southern Ontario.

Full-grown larvae of Zeiraphera pacifica Freeman and Epinotia hopkinsana (Kearfott) are described and figured.

Studies on the biology of Encarsia pergandiella Howard, a solitary, arrhenotokous endoparasite, revealed that fertilized eggs, which give rise to females, are deposited in whitefly nymphs preferably in second, third or fourth instar, while unfertilized eggs, which give rise to males, are deposited in Encarsia larvae at whose expense they develop. The parasite adults were observed to feed on body fluids of whitefly nymphs. Both sexes have a pupal and three larval stages, and development from egg to adult at approximately 75° F. takes 15 days for the females and 13 to 14 days for the males. Mean longevity of the females at constant and fluctuating temperatures was studied. Actual mean fecundity at 75 ± 4° F. was 48.5 eggs per female, all of which were deposited during the first 70% of her life, provided hosts were abundant. Field observations revealed that E. pergandiella was present throughout the year, reaching highest numbers in the spring and summer. The parasite does not have an obligatory period of dormancy for all of its individuals. E. pergandiella was not able to prevent whiteflies from causing heavy damage to plants. The reason may be in the discrepancy between the rate of increase of the whitefly and the parasite.

The species of Megathopa, Canthon, and Deltochilum included in the Biologia Centrali-Americana are discussed, information on distribution is included, and references affecting the status of some of the species are cited. Lectotypes are designated for Canthon lamprimus Bates, Deltochilum parile Bates, Deltochilum gibbosum sublaeve Bates, Deltochilum lobipes Bates, and Deltochilum scabriusculum Bates. The following new species and subspecies are described: Canthon morsei from Veracruz, Mexico, Canthon coahuilenis from Coahuila, Mexico, Deltochilum gibbosum panamensis from Bocas del Toro, Panama, Deltochilum scabriusculum montanum from Sonora and Sinaloa, Mexico, and Deltochilum tumidum from Mexico, Morelos, and Sinaloa, Mexico.

Sequential sampling, in which decisions depend upon the accumulated results of a series of observations, leads to considerable saving of time and money. A sequential plan, based on the negative binomial distribution and providing for population estimates in three infestation categories, was drawn up for use in control of the imported cabbageworm, Pieris rapae (L.), on cabbage. An appraisal of the plan under field conditions showed that it reduced the sampling time by 75% while rating the infestation correctly in 94 of 100 cases. With the six discrepancies, population means lay between the limits set for the infestation categories.

Five Cretaceous fossil aphids from Canadian amber are described. All are new species and none is referable to an extant genus. The names assigned to these are as follows: Palaeoaphis archimedia, Ambaraphis costalis, Alloambria caudata, Pseudambria longirostris and Aniferella bostoni. Two new subfamilies have been proposed for four of them and the fifth has been placed in the Neophyllaphidinae, which was previously considered a tribe in the Callaphidinae. One new subfamily, the Palaeoaphidinae, is exceptionally primitive and the two included species, P. archimedia and A. costalis, have more antennal segments and a more primitive wing venation than any known aphid. The cubitus vein in these species is more like that of the Psyllidae and of the extinct Permian Archescytinidae than that of existing Aphidoidea. The venation of the other new subfamily, the Canadaphidinae, shares some similarities with the unipterine aphids that occur on the Combretaceae in Africa.

The main features of the evolution of the aphid wing are discussed as an aid in placing the fossils with respect to current concepts of aphid classification.

The westermanni group of the genus Euxoa is defined, and a key to the eleven constituent North American species is presented. Two species are described as new: chimoensis from Fort Chimo, Quebec, and luteomaculata from montane areas of southern Alberta, southern British Columbia, and northern Washington.

The effects of fluctuating water tables on the survival of the larch sawfly, Pristiphora erichsonii (Hartig) (Hymenoptera: Tenthredinidae), were studied by burying cocoons at different depths in a tamarack bog. Most larvae in cocoons flooded during August or September died before winter. The percentage of overwintering survival of unflooded cocoons remained constant from late fall until development began in the spring. The higher the cocoons were above the maximum water table during August and September, the greater was the percentage of overwintering survival and subsequent adult emergence.

The boxelder leaf gall midge is univoltine in Michigan. Adults emerge after the first few warm days in April, and deposit numerous eggs within the folded young leaves of boxelder (Acer negundo L.). Larval eclosion occurs a few days later, and gall development begins shortly after. Head capsule measurements revealed three larval instars. Third-instar larvae drop to the ground near the end of May, work their way into the soil, and construct cocoons. Pupation occurs in late August, and overwintering takes place in the pupal stage. Because oviposition occurs almost always on leaves in a certain stage of development and an estimated 50% of leaves will therefore escape attack, host mortality apparently cannot be caused by this insect.