Food webs in the real world are much more complex than food-web literature would have us believe. This is illustrated by the web of the sand community in the Coachella Valley desert. The biota include 174 species of vascular plants, 138 species of vertebrates, more than 55 species of arachnids, and an unknown (but great) number of microorganisms, insects (2,000-3,000 estimated species), acari, and nematodes. Trophic relations are presented in a series of nested subwebs and delineations of the community. Complexity arises from the large number of interactive species, the frequency of omnivory, age structure, looping, the lack of compartmentalization, and the complexity of the arthropod and soil faunas. Web features found in the Coachella also characterize other communities and should produce equivalently complex webs. If anything, diversity and complexity in most nondesert habitats are greater than those in deserts. Patterns from the Coachella web are compared with theoretical predictions and "empirical ge...

Complex trophic interactions in deserts: an empirical critique of food-web theory

Following observations of mass spawning of hermatypic corals on the Great Barrier Reef in 1981 and 1982, spawning dates were successfully predicted and documented at five reefs on the Central and Northern Great Barrier Reef in 1983. During the predicted times, 105 species from 36 genera and 11 families were observed to spawn. Of these, 15 species were shown to have an annual gametogenic cycle. All but two of the species observed during mass spawnings shed gametes which underwent external fertilization and development. Synchronous spawning was observed both within and between the five reefs studied, which were separated by as much as 5° of latitude (500 km) or almost a quarter of the length of the Great Barrier Reef. The mass spawning of corals took place on only a few nights of the year, between the full and lastquarter moon in late spring. Maturation of gametes coincided with rapidly rising spring sea temperatures. Lunar and diel cycles may provide cues for the synchronization of gamete release in these species. The hour and night on which the greatest number of species and individuals spawned coincided with low-amplitude tides. Multispecific synchronous spawning, or "mass spawning", of scleractinian and some alcyonacean corals represents a phenomenon which is, so far, unique in both marine and terrestrial communities.

Synchronous spawnings of 105 scleractinian coral species on the Great Barrier Reef

Ichnology is the study of traces created in the substrate by living organisms. This is the first book to systematically cover basic concepts and applications in both paleobiology and sedimentology, bridging the gap between the two main facets of the field. It emphasizes the importance of understanding ecologic controls on benthic fauna distribution and the role of burrowing organisms in changing their environments. A detailed analysis of the ichnology of a range of depositional environments is presented using examples from the Precambrian to the recent, and the use of trace fossils in facies analysis and sequence stratigraphy is discussed. The potential for biogenic structures to provide valuable information and solve problems in a wide range of fields is also highlighted. An invaluable resource for researchers and graduate students in paleontology, sedimentology and sequence stratigraphy, this book will also be of interest to industry professionals working in petroleum geoscience.

Ichnology: Organism-Substrate Interactions in Space and Time

Controversy exists over ecological risks in classical biological control. We reviewed 10 projects with quantitative data on nontarget effects. Ten patterns emerged: (a) Relatives of the pest are most likely to be attacked; (b) host-specificity testing defines physiological host range, but not ecological range; (c) prediction of ecological consequences requires population data; (d) level of impact varied, often in relation to environmental conditions; (e) information on magnitude of nontarget impact is sparse; (f) attack on rare native species can accelerate their decline; (g) nontarget effects can be indirect; (h) agents disperse from agroecosystems; (i) whole assemblages of species can be perturbed; and (j) no evidence on adaptation is available in these cases. The review leads to six recommendations: Avoid using generalists or adventive species; expand host-specificity testing; incorporate more ecological information; consider ecological risk in target selection; prioritize agents; and pursue genetic data on adaptation. We conclude that retrospective analyses suggest clear ways to further increase future safety of biocontrol.

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Nontarget effects--the Achilles' heel of biological control? Retrospective analyses to reduce risk associated with biocontrol introductions.

The dominant feature of fruit fly research over the past decade has been a considerable preoccupation with projects related to the suppression or eradication of populations by the release of sterile individuals. The success of the eradication campaigns against the screwworm fly, Cochliomyia hom­ nivorax, (16), followed by further successes against the melon fiy, Dacus cucurbitae, and the Oriental fruit fiy, Dacus dorsalis, by Steiner and his associates in the Mariana islands (147, 149), has engendered considerable enthusiasm for the sterile male technique among those concerned with the control of fruit flies. Entomologists concerned with many other groups of insects are turning more and more toward pest management (37, 122) or "integrated" proce­ dures of control based on solid ecological foundations. These methods aim, not at the complete destruction of the pest population, but at its reduction to a low mean level of abundance, so that its fluctuations seldom or never carry it above its economic threshold. But for fruit flies, particularly in situ­ ations where fruit is grown for export to uninfested areas, or where con­ sumers demand a "perfect" product, the economic threshold may often be near zero, and the strong preference for eradicative rather than "management" procedures is readily understandable. '

The Ecology of Fruit Flies

The oriental fruit fly, Dacus dorsalis Hendel, is widely distributed along the arc from India to Indonesia to Formosa, and in the Mariana Islands. In 1946 it was discovered in Hawaii for the first time and within 2 to 3 years developed into an agricultural problem of major proportions. The devastating effects of the fly on many crops in Hawaii and the potential threat of introduction to the mainland of the United States, led to the esta blishment of a cooperative research program including agencies of the (then) Territory of Hawaii, the Federal government, private research stations and subsequently the State of California (Clausen, Clancy and Chock 1965, pp. 1-7).

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Biotic Factors Influencing Populations of Dacus dorsalis in Hawaii

Echiniscus viridis (Tardigrada): Fine Structure of the Cuticle

THE SUBFAMILY Johnstonianinae Thor 1935 (Trombidiidae) was established to include Johnstoniana George 1909 and related genera. The only comprehensive treatment of the group was published by Thor and Willmann (1947) who included eight species in the genera Centrotrombidium Kramer 1896, Johnstoniana, Diplothrombium Berlese 1910, Myrmicotrombium Womersley 1934, and Hirstithrombium Oudemans 1928. The present study was undertaken with a view to placing the systematics of the Johnstonianinae on a sound morphological basis, and to detGrmine the relationship of the group to other terrestrial Parasitengona. It soon became apparent that the mites included in the Johnstonianinae differed so significantly from other terrestrial Parasitengona that they could not logically be retained within the family Trombidiidae Murray 1877. The differences are much greater than those which have been cited, for example, to establish Trombiculidae Ewing 1944 as a family separate from the Trombidiidae. The group is therefore raised to family rank with Johnstoniana George 1909 as the type genus. Interest in the group was stimulated by numerous indications that this is perhaps the most primitive existing family, terrestrial or otherwise, within the Parasitengona. The indications of this are of ecological, behavioral, and morphological nature.

Studies on the Johnstonianidae (Acari, Parasitengona)

Although mentioned frequently in acarological literature, the genus Balaustium is poorly known. In recent years authenticated cases of attacks on man have shown the need for accurate information on feeding habits in this genus. Observations by the writer and others show that species of Balaustium have very generalized feeding habits. Food sources include pollen, leaf tissues, and insects. Man is also attacked, probably in situations which bring numbers of Balaustium into incidental contact with potential human victims. Symptoms of attack vary widely, probably as a result of individual susceptibility, or possibly with the species of Balaustium involved. Information on the latter point is not available at present because of the inadequate state of our knowledge of the systematics of this genus. The cosmopolitan genus Balaustium was first described by Von Heyden in 1826, with Trombidium murorum Hermann, 1804, as type species. About 40 or more species have been ascribed to the genus subsequently from most parts of the world, but the descriptions of these have been so brief and the diagnostic characters so little known that it is impossible to say at the present time just how many species are involved. Likewise, very little has been written about their biology, especially about their parasitic relationships with other organisms. These mites have a characteristic body form (Figs. 2, 3) and are generally brick-red or brown in color, sometimes with a metallic green sheen. When fully mature they measure between 1.0 and 1.5 mm in length, exclusive of the appendages. The legs are relatively short, with legs I about as long as, or slightly shorter than, the body (Fig. 1) in contrast with many other Erythraeidae in which one or more pairs of legs are markedly longer than the body. They can be differentiated readily from closely related short-legged Erythraeidae by the possession of a single pair of eyes, behind which is a pair of glandular openings Received for publication 15 January 1963. * This study is being supported by a grant (E2533) from the National Institutes of Health, Public Health Service, to the University of California, Riverside. borne on collarlike tubercles. Superficially, these tubercles give the mite the appearance of having two pairs of eyes (Fig. 3). They are absent in the larva but are present in the active nymphs and the adults.' Species of Balaustium are found on a variety of substrates including soil litter of many types, the trunks of trees, the leaves or flowers of plants, and on stone walls and other structures. The adults are often extremely aggressive predators of small insects, including the nymphs of Hemiptera, Thysanoptera, and other orders. It does not appear that they are very specific in the hosts that they select, although information along this line is not adequate to justify any general statements. The writer has seen unusually heavy populations on Artemisia, Ribes, Quercus, and other plants sufficiently numerous and various to indicate that species of Balaustium may become abundant under a variety of environmental conditions. The writer assumes, as did Oudemans, Grandjean, and other workers, that the short-legged Erythraeidae with elevated openings dorsally just posterior to the eyes are congeneric with Trombidium murorum Hermann, 1804. As Grandjean (1947, 327-328) has pointed out this assumption is arbitrary and not capable of demonstration. Nevertheless, the writer feels that this assumption is justifiable on the grounds of probability and in the interest of nomenclatorial stability. Southcott (1961, 540-548) summarized much of the information presently available on the European species.

Feeding habits in the genus Balaustium (Acarina, Erythraeidae), with special reference to attacks on man.

Paper chromatography using a 4 to 1 mixture of white kerosene and xylene was used to characterize the pigmentation of nine species of spider mites. Pigmentation was complex, and 10 constituents were isolated from the citrus red mite. From Re values, fluorescence, and absorption spectra it was determined that the biochromes are derived from dietary chlorophylls and carotenoids.

Irwin M. Newell

Papers

Biotic Factors Influencing Populations of Dacus dorsalis in Hawaii

Echiniscus viridis (Tardigrada): Fine Structure of the Cuticle

Studies on the Johnstonianidae (Acari, Parasitengona)

Feeding habits in the genus Balaustium (Acarina, Erythraeidae), with special reference to attacks on man.

Investigation of the Biochromes of Mites