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Byline: Gordon Pritchard The old joke about the print shop of the future might be not far off the mark: "There will be only two employees: a guard and a [...]

Though frequency-modulation (FM) technique can never replace amplitude-modulation (AM) halftones completely, Creo's stacatto techinque helps FM to gain an upper hand over the AM in seven screening reproduction problems.

AbstractLarval growth rate has the same temperature coefficient in three species of coenagrionids, but Argia vividaand Amphiagrion abbreviatum, which frequently live in geothermally heated water, grow fastest at 29.0–30.0°C compared with 23.4°C for Coenagrion resolutum, which lives in cooler water. Survival below 15°C in the laboratory was much better in C. resolutum.These characteristics are reflected in the distributions of the three species, C. resolutumranging much further north in North America than the other two species, but not penetrating as far south. By contrast, the temperature coefficient for Lestes disjunctusis higher than that of the coenagrionids, and this is related to a different life history. In the coenagrionids, one or more winters are spent in the larval stage. In L. disjunctus, winter is spent in the egg stage, and larval growth must be completed quickly.

AbstractAlthough Amphiagrion abbreviatum(Selys) and Argia vividaHagen often occur at the same geothermally heated springs in western Canada and the United States, they differ markedly in their abundance at any particular site. There is no relationship between crude data on water temperature, conductivity, or aquatic vegetation and the relative abundance of the two species, but there is a striking correlation with presence or absence of trees. The absence of A. abbreviatumfrom heavily treed areas is associated with the paucity of suitable daytime perching sites, and there may be competitive pressure exerted by A. vividafor the perching sites that are available. Argia vividadoes not live at open sites because it requires trees for night-time roosts. Argia vividaroosted higher than A. abbreviatumin cages and held the body at a greater angle from the cage wall. The roosting posture of A. vividais probably related to interception of solar radiation in the morning, and the body positions of both species possibly provide defence against predation.

AbstractMayflies of the genus Ameletus(Ephemeroptera: Ameletidae) occur in practically every drainage of western Alberta and in the Cypress Hills, from headwater spring brooks to larger rivers. The genus is speciose and reaches its greatest diversity in the southwestern part of the province where as many as 12 species can occur at a single site. Of the 30 bisexual species currently recognized from North America, 13 have been collected from Alberta (A. bellulus, A. celer, A. cooki, A. majusculus, A. oregonensis, A. pritchardi, A. similior, A. sparsatus, A. subnotatus, A. suffusus, A. validus, A. velox, and A. vernalis), and another, A. inopinatus, is assumed to occur in the northern part of the province. Male adults of all North American species were described previously by Zloty (1996, The Canadian Entomologist128:293–346). In the current paper, we describe late-instar larvae and adult females of all 14 Albertan species, and provide species distributions and keys for identification of male and female adults and larvae. All diagnostic taxonomic characters are described and illustrated. The identification keys can also be used in Saskatchewan, eastern British Columbia, Montana, and the northern parts of Idaho and Washington.

AbstractTipula paludosaspends increasing periods of time in a pharate condition with each succeeding molt. The pupa is entirely pharate since larval–pupal ecdysis coincides with pupal–adult apolysis, and the larger part of the adult instar is also spent in a pharate condition. The fact that the instar usually referred to as the pupa is actually a pharate adult should be clearly understood by physiologists, ethologists, and ecologists.

AbstractSamples of a population of Argia vividaHagen larvae were taken at about monthly intervals from a series of warm sulphur pools at Banff, Alberta, from June 1973 to December 1974. Changes in head capsule width and wing pad length in field-collected and laboratory-reared specimens show that the life-cycle is univoltine. Only the final (Z) instar can be recognized with certainty, but methods are described whereby the population can be divided into size classes which are thought to correspond well with the last nine larval instars. Periods of rapid growth occur in the autumn and again in the spring. Larvae overwinter in the instars U, V, W, X, and Y and the major shift to the final instar occurs in March and April. Adults emerge from April to August. In the laboratory, growth is temperature dependent until the penultimate (Y) instar and this could be a factor in the field since, although larvae can exist year-round at a constant 26 °C, some larvae live in the cooler areas at the edges of the streams and pools. Entry to the final instar appears to require the long photoperiods that follow the vernal equinox.

AbstractGrylloblatta campodeiformisWalker were collected from a site in the Alberta Rocky Mountains at an altitude of 1300 m. The gut contents in the autumn consist almost entirely of arthropods. Dominant among these was a tipulid fly, equally typical of the cold, montane habitat as Grylloblattaitself. In the laboratory, G. campodeiformisadults eat only live or recently killed animal prey, and neither adults nor larvae grow without animal food. Prey is detected by the antennae and then seized by the mandibles. Five types of sensilla, all of which are probably involved in prey identification, are described from the antennae and palpi.

AbstractThe prey of adult dragonflies has been studied by the analysis of gut contents and was found to consist mainly of small Diptera. Most of the prey is very small but large dragonflies, such as aeshnids, occasionally take larger prey, such as caddis flies and other dragonflies. Relatively little diminution in the numbers of adult mosquitoes can be expected to occur as a result of dragonfly predation, because of the different conditions required for flight by dragonflies and mosquitoes.

The article presents questions and answers related to guitar including the information on luthier Craig Pederson, the nontropical materials for fingerboards, and the placement of the nut and additional fret in 7-string guitar.