Paul DeBach

Biological Control of Coccids by Introduced Natural Enemies

Scale insects and mealybugs (Homoptera: Coccoidea) have been the targets of numerous successful biological control projects. The first spectacular success in the history of biological control was achieved against a coccid pest, the cottony cushion scale, Icery a purchasi Maskell, in California in the late 1880’s. A predatory ladybeetle, Rodolia cardinalis (Mulsant), introduced from Australia, was credited with the rapid, complete and permanent control of this serious pest in California. Subsequently, the same predator achieved complete biological control of the cottony cushion scale in 25 additional countries, and a substantial degree of control in four other countries (see DeBach, ed., 1964, Chapter 24).

Experimental Techniques for Evaluation of the Effectiveness of Natural Enemies

The role of natural enemies in prey (or host) population regulation has long been debated by ecologists, and various methods of evaluation proposed and attempted. The fact that considerable disagreement remains is sufficient evidence of the need for adequate assessment of the efficiency of enemies. Precise means of evaluation are needed for several reasons: (1) to illuminate basic principles of population ecology, especially the role of biotic and abiotic factors, (2) to furnish a sound ecological basis for manipulation of natural enemies either by demonstrating the need for importation of new ones or by showing that the established ones are rendered ineffective due to interference phenomena, including pesticides, weather or cultural practices, and (3) to provide the proof of effectiveness of natural enemies that is necessary in applied biological control in order to justify needed increased research and development support.

Effects of Parasite Population Density on Rate of Change of Host and Parasite Populations

The agencies in nature that influence population trends and levels of species are so numerous, and so interdependent and complex, that the only hope of understanding them appears to lie in studying the factors separately or in small related groups. The immediate objective is to reconstruct the effective environment by a sort of synthetic process, and the ultimate objective is to make it possible to evaluate the separate agencies by statistical analyses of field data. It is, of course, well known that population changes are associated with nutrition, with weather, with competition, with inherent changes in fecundity, and with the incidence of disease, parasites, and predators. The results of a considerable amount of research in these fields have been recorded. The writers will not undertake to discuss here these advances, as it would lengthen the paper unduly. Those interested in the causative agencies in population dynamics should refer to the various papers by: Thomas Park and associates on the effect of nutrition, and of competition, both interand intra-specific; Raymond Pearl, R. N. Chapman, V. Volterra, Janet Boyce, John Stanley, D. S. MacLagan, and A. C. Crombie on competition; F. S. Bodenheimer, James Davidson and associates, B. P. Uvarov, V. E. Shelford, L. C. Birch, and W. F. Cook on weather; and Paul Errington, G. F. Gause, A. J. Nicholson, W. R. Thompson, G. Salt, Marjory Walker, and Joyce Laing on

Effects of temperature and host age upon the encapsulation of Metaphycus stanleyi and Metaphycus helvolus eggs by brown soft scale Coccus hesperidum

Abstract Encapsulation of eggs inserted by Metaphycus stanleyi (Hymenoptera: Encyrtidae) into the brown soft scale Coccus hesperidum (Homoptera: Coccidae) became more frequent as the host matured. This occurred with both laboratory reared and field-collected parasites. After parasitism for 24 hr at 27°C, encapsulation frequency did not differ in hosts reared at 20° or at 27°C, but significantly increased in hosts reared at 33°C. When parasitism and rearing were carried out at the same temperature, the percentage of eggs encapsulated increased from 48.7% at 27°C to 94.1% at 33°C. With M. helvolus, the percentage of eggs encapsulated was considerably higher than with M. stanleyi; e.g., 99.3 vs 48.7%, respectively, at 27°C. At 20° and 27°C, some M. helvolus development occurred in the larvae of brown soft scale but none at 33°C; the adult stages of the host encapsulated all the parasite eggs at these temperatures.

Development of Habrolepis rouxi Compere (Hymenoptera: Encyrtidae) in two armoured scale hosts (Homoptera: Diaspididae) and parasite egg encapsulation by California red scale

Abstract. 1. California red scale Aonidiella aurantii (Maskell) and oleander scale Aspidiotus nerii Bouché (Homoptera: Diaspididae) are not completely suitable for the development of the encyrtid endoparasite Habrolepis rouxi Compere.

EXPERIMENTAL STUDIES ON HYBRIDIZATION AND SEXUAL ISOLATION BETWEEN SOME APHYTIS SPECIES (HYMENOPTERA: APHELINIDAE). III. THE SIGNIFICANCE OF REPRODUCTIVE ISOLATION BETWEEN INTERSPECIFIC HYBRIDS AND PARENTAL SPECIES

Interspecific hybridization is of rare occurrence in animals, especially in comparison to plants, obviously because of their very different modes of reproduction, ecology, and perhaps especially, of behavioral isolation (Mayr, 1963). Within the animal kingdom, hybridization frequency differs with the class, being more characteristic of animals which reproduce by means of external fertilization, e.g., fishes and amphibia. To illustrate this rarity of animal hybrids in nature, Mayr (op. cit.) states that perhaps one out of 60,000 wild birds is a hybrid. In animals with internal fertilization, the rarity of hybrids may frequently be attributed to the presence of ethological isolating mechanisms. Where ethological isolating mechanisms are overcome, either under laboratory or natural conditions, and successful interspecific copulation occurs, hybrids may occasionally be produced. The steps in hybrid production subsequent to mating, such as fertilization of the egg by the foreign sperm, development of the embryo, etc., should proceed normally. These may be prevented by death of the sperm in the female genital tract, inability of the sperm to fertilize the egg, or by subsequent death of the zygote due to genetic imbalances. Even when all these isolational barriers are circumvented and hybrids are produced, poor genetic fit (brought about as a result

Effects of short-duration sub-optimum pre-oviposition temperatures on progeny production and sex ratio in species ofAphytis (Hymenoptera: Aphelinidae)

In biological control research, the effect of temperature on parasites plays a highly important, multifaceted, but frequently neglected role. Obviously, other factors such as humidity or food are important and essential, but the present interest lies solely with effects of temperature. In the insectary the most efficient culture method must be based upon a detailed knowledge, not necessarily of just one opt imum temperature but of a variety of opt imum temperatures, for there may be different optima for copulation and insemination, rate of oviposition, total oviposition, rate of development of immature stages, survival of ova, sperm, and immature stages, or longevity of adults. Frequently, adult parasites are stored or held at cool or even quite cold ~emperatures preceding colonization in the field, laboratory testing, or laboratory culture. The results reported later in this paper will show that seemingly mild and safe storage temperatures (60 ~ to 69~ range) may have a much more profound adverse effect than has been suspected. Such temperatures can, in fact, be so serious that females stored for only a few days may suffer nearly complete reproductive sterilization. The effect of temperature on parasite populations in the field and in the laboratory has been dealt with by several authors (BURNETT 1949, DEBAcH 1965, DEBACH, FISHER, and LANDI 1955, DEBAc~ and SISOlEVld 1960, LORD and MAcPHEE 1953, PICKETT 1965). The understanding of such effects is obviously of basic ecological importance and may furnish the information necessary for the success of operations involving periodic colonization, or other manipulation of parasites whose populations periodically are depressed by temperature extremes. I t may also help explain the

Resurrection of Aphytis Theae (Hymenoptera: Aphelinidae), A Parasite of Tea Scale, with Notes on a New Group of Species

Aphytis theae (Cameron), recently introduced from India into Florida for the biological control of the tea scale, Fiorinia theae Green, is redescribed. The funicularis group is established for species of Aphytis with 5-segmented antennae and reduced mouthparts, including A. funicularis Compere, A. gordoni DeBach and Rosen, A. theae and A. ulianovi Girault. A key to the 4 members of the new group is presented.

A new species ofAphytis that attacks important armored scale insects

Aphytis roseni spec. nov. is described and its affinities with other members of the genus indicated. The parasite was imported into Peru from Africa for control of the rufous scale,Selenaspidus articulatus (Morgan). In Peru,A. roseni is achieving substantial biological control.RésuméAphytis roseni spec. nov. est décrite et ses affinités avec les autres membres du genre sont indiquées. Ce parasite a été introduit au Pérou pour la lutte contre la cochenille rouge,Selenaspidus articulatus (Morgan). Dans ce pays,A. roseni assure une lutte biologique efficace contre la cochenille.

The Chilensis Group

This small, rather heterogenous group at present includes cercinus Compere, chilensis Howard, columbi (Girault), faurei Annecke, and merceti Compere. Of these members, three are Ethiopian, one is Australian, and one is nearly cosmopolitan in distribution. One Oriental species, antennalis n.sp., is provisionally referred to this group.