Stanley E. Flanders

On the Sexuality and Sex Ratios of Hymenopterous Populations

The sexuality and primary sex ratios in populations of many species of Hymenoptera are functions of the environment, the environment acting indirectly on a preembryonic stage of the individual, changing it either from potentially female to male or from potentially male to female. Ten secondary phenotypic factors affecting sex-ratios are listed.

DIFFERENTIAL HOST RELATIONS OF THE SEXES IN PARASITIC HYMENOPTERA1

The divergent ontogeny of the male, a unique phenomenon characterizing certain genera of the Aphelinidae, has its physiological bases in the environmental control of sex permitted by the haploid origin of the male and the diploid origin of the female and in the efficiency of the chalcidoid type of spermatheca which, during the process of oviposition, brings the environmentally activated sperm into contact with the egg. This divergence is correlated with the sexual dimorphism and the sexual ditrophism of the early developmental stages. It is psychologically manifested in a number of species by a marked difference in the host relations of the aphelinid female before and after mating. The climax of differential host relations within a species is the production of the female in a coccid host and the production of the male in a lepidopterous host. The aberrant development of the male tends to increase the capacity of the species to survive at low host densities.

Deviate-ontogenies in the aphelinid male [Hymenoptera] associated with the ovipositional behavior of the parental female

ZusammenfassungIntrapezifische Geschlechtsunterschiede in den Beziehungen zum Wirt, die sich in einer abweichenden Männchen-Entwicklung ausprägen, kennzeichnen 45 Arten in 8 Gattungen derAphelinidae. Diese abweichende Männchen-Entwicklung ist bei den verschiedenen Arten entweder unabhängig oder abhängig von der Lage des haploiden Eies am Wirt.Bei 8 Arten (Gruppe I) ist die Geschlechtsdifferenzierung in der Beziehung zum Wirt unabhängig von der gewöhnlichen Plazierung der haploiden und diploiden Eier. Die Unterschiede treten erst nach der Eiablage und der Vollendung der Embryonalentwicklung auf.Bei 3 Arten (Gruppe II A-1) ist die unterschiedliche Plazierung haploider und diploider Eier und die darauf folgende Verwirklichung einer unterschiedlichen Entwicklung ein psychologischer Effekt, der von einem reversiblen physiologischen Zustandswechsel der Spermathecen-Drüse des begatteten Weibchens herrührt.Bei 27 Arten (Gruppe II B) und bei 2 Arten (Gruppe II A-2) verursacht die Kopula eine vollständige Umstellung bei der üblichen Plazierung der Eier, wobei die haploiden Eier von dem unbegatteten Weibchen an oder in parasitischen Hymenopteren oder in Lepidopteren-Eier abgelegt werden, während diploide Eiver von dem begatteten Weibchen an oder in Homopteren plaziert werden. Diese Umstellung führt dazu, dass die Nachkommen begatteter Weibchen alle weiblich sind.Bei 5 Arten der GattungCasca (Gruppe III) ist die Sonderentwicklung der Männchen vielleicht auf deren Embryonalperiode beschränkt. Eine unterschiedliche Plazierung haploider und diploider Eier mag daraus geschlossen werden, dass bei mehreren Arten alle Nachkommen begatteter Weibchen weiblich sind.

The Bisexuality of Uniparental Hymenoptera, a Function of the Environment

REPRODUCTION in the Hymenoptera is characterized by the production of uniparental apomictic2 individuals. The normal male, always uniparental, is haploid. The female, either uniparental or biparental, is diploid. In a uniparental species, the progeny of unmated females are usually females; in a biparental species, usually males. There is, however, in many if not all hymienopterous species, a capacity to produce both sexes uniparentally (amphitoky). This uniparental bisexuality, as recorded for a number of hymenopterous species, appears to be an effect of environmental factors. The purpose of this paper is to present evidence supporting the thesis that the sexuality of a uniparental population is an expression of the type of germinal tissue in the preceding generation, the type being determined by environmental conditions. The observations forming the basis of this study were made during the mass propagation of beneficial insects at the University of California Citrus Experiment Station, Riverside, California.

Fecundity of Entomophagous Insects Under Mass Culture, An Effect of Environmental Resistance

The mass culture of entomophagous insects for use in biological control work involves the propagation of such insects at high population densities in artificial environments under exacting procedures of handling. With populations under these conditions, as in the field, environmental resistance is the principal factor limiting production. (A population consists of two or more individuals of a species, each of which may influence the activity of another.) The purpose of this paper is to outline the types of culture methods that have been developed, and to analyze the fecundity of propagated species in relation to environmental resistance and methods used. There are a number of species of entomophagous insects for which more or less standardized methods of mass culture have been developed. Some of these species, and the food material involxed in their production, are as follows: Cryptolaetu its alontroutcieri, in production for the past 30 years, using mealybugs on potato sprouts (Smith and Armitage 1931); Trichogramnima ezvaniescens, in production for the past 26 years, using eggs of the Angoumois grain moth (Flanders 1930) ; Leptoniiastix dactylopii, in production for the past 18 years, using mealybugs on potato sprouts (Flanders 1949); Metaphycus helvolus, in production for the past 14 years, using black scale on potato sprouts (Flanders 1949). Within the past 13 years illicroplectron fuscipennis has