George F. Edmunds

Selection, Outbreeding Depression, and the Sex Ratio of Scale Insects

The black pineleaf scale insect has haploid males and diploid females. Ratios of males to females late in development ranged from 0.005 to 0.320 among insect subpopulations that were infesting different host trees. Demes well adapted to an individual ponderosa pine had a higher proportion of males than did demes that were poorly adapted to the host. Ratios of males to females rose in successive annual samples as natural selection increased insect adaptation. Gene flow between demes on different host trees produced predictable changes in the sex ratio.

Responses of Black Pineleaf Scales to Host Plant Variability

Plants use various means to deter or dissuade attack by phytophagous insects. Herbivore counteradaptation to these defenses is probably an important factor in insect host specificity and the coevolution of plant and herbivore phylogenies. This coevolutionary interaction is particularly interesting among long-lived forest trees and their associated insect fauna. One would think that the longevity of trees is a severe disadvantage in the coevolutionary interaction with short-lived insects; their relative success in spite of such herbivores invites further inquiry.

A New Genus and Species of Leptophlebiidae: Atalophlebiinae from the Celebes (Sulawesi) (Ephemeroptera)

Sulawesia a new genus of the Leptophlebiidae: Atalophlebiinae is established based on the adults and nymph of a new species, S. haema from the Celebes (Sulawesi). Sulawesia belongs to the Atalophlebioides lineage and is closely related to genera in Australia. The zoogeography of Sulawesia is discussed.

Incidence of basal needle necrosis of pines in relation to environmental factors

Abstract Basal needle necrosis (BNN) of pines is characterized by necrotic lesions on the surface of needles within the needle sheath, with or without hypertrophy or needle splitting and resin exudation. Interpretations vary on the possible association of BNN with atmospheric sulphur dioxide or hydrogen fluoride pollution. In this study there is no correlation of the frequency of BNN of ponderosa and Scotch pines with foliar fluoride in the ranges of 1 to 229 μg g −1 (dry weight, as F) or sulphur content of needles (0·057 to 0·153%, dry weight as S), or with a combined fluoride-sulphur index in the western areas of the United States sampled. Hence, these air pollutants appear to play no causal or contributory role in B N N frequency. No other environmental factor emerged in the study as a likely cause of the syndrome. No correlation of B N N was found with the number of years the needles are retained or tree condition (crown fullness and colour), indicating that the syndrome is of little or no economic significance in pines. A significant correlation of B N N frequency with the amount of debris between the needle bases in the fascicle is equivocal as to cause and effect; the debris may have a causal role in B N N, or B N N-caused exudates may cause debris to be retained.

The larvae of the Madagascar genus Cheirogenesia Demoulin (Ephemeroptera: Palingeniidae)

Generic characteristics of the larval stage of Cheirogenesia Demoulin are described and illustrated in detail for the first time. Fontainica josettae McCafferty is shown to be a junior synonym of Cheirogenesia decaryi (Navas) syn.n., and a specific description of the larvae is given. Notes on the probable relationships of this Madagascar genus and on the biology and habitat of the larvae are included.