Stanley W. Szczytko

Life cycle and production of Isoperla signata (Banks) in a Central Wisconsin trout stream

The life history and production of the stonefly Isoperla signata (Banks) was studied in a central Wisconsin trout stream for one year. Adults exhibited a 2 week spontaneous emergence beginning in early May when mean daily stream temperatures were approximately 10°C. Emergence was completed and no larvae remained in the stream when mean daily stream temperatures reached 18°C. Ova were oval in shape, round in cross section and measured 250μm (ira long by 195 μm wide. Ova exhibited a differential hatch which lasted approximately 51 days and underwent a mean incubation period of approximately 36 days. Larvae exhibited an S2 (slow) univoltine life cycle and were present in the stream for approximately 11 months. The cohort production interval (CPI) was 329 days. Size frequency distributions indicated ca. 14 instars for both males and females. Size of male and female larvae were similar until the 9th instar, but females always weighed more than males. The mean cohort standing crop and biomass were 119 N m‐2 and...

Systematic studies on western palaearctic perlodini (Plecoptera: Perlodidae)

A review of the western Palaearctic perlodine genera, Besdolus Ricker, Diclyogenus Klapalek and Isogenus Newman indicates Besdolus must be placed in synonymy with Dictyogenus. Guadalgenus, a new monotypie genus from Spain, is erected for Isogenus franzi (Aubert). The new genus is distinguished from Dictyogenus and Isogenus by absence of lateral stylets and by a distinctive caudal epiproct sclerite in the male, by absence of a tufted lacinial knob in nymphs and by absence of a collar in the egg.

A new species of Neoperla (Plecoptera: Perlidae) from Burma

Abstract Neoperla kachin sp. n. is described from Myitkyina, Burma, and ♂ holotype and ♀ allotype specimens are designated. Original drawings of ♂ and ♀ genitalia and SEM photomicrographs of the eggsupport the description.

The Language of Stoneflies

species to reach these islands. Assumptions upon which these conclusions rest and alternative explanations for the results are discussed in the original paper, and two areas of ignorance in need of empirical investigation are emphasized. The first is the set of conditions that determine the establishment of a breeding population on an island; food supply and competition are not the sole factors. The second is the extent of competition for food over long periods of time in a temporally fluctuating environment. o islands by the lack of suitable foods or by the ailure of the

Skwala brevis (Koponen) from Japan (Plecoptera: Perlodidae)

Abstract Skwala brevis (Koponen) is reported for the first time from Japan and a description of the egg is presented based on SEM photomicrographs of Soviet and Japanese specimens.