Showing papers in "Biological Journal of The Linnean Society in 1979"

The relationships of plant and insect diversities in succession

Abstract: The basic features of an intensive study on the various stages of a secondary succession, from fallow Held to birch woodland, are described. The α-β diversities of the green plants, and two orders of insects, Hetcroptera and adult Coleoptera, are described. For the vegetation, in addition to taxonotnic diversity, structural diversity, with both spatial and architectural components, was recognized. It was found that up to a successional age of 16 months, the taxonomic diversities of plants and insects rose; thereafter the diversity of the plant species declined far more than the insect species diversity. It was concluded that in the later successional stages the maintenance of a high level of taxonomic diversity of these orders of insects is correlated with the rising structural diversity of the green plants, which virtually compensates for their falling taxonomic diversity. The larger fungi appear to show a similar trend to the insects.

Patterns of ecological diversity in fossil and modern mammalian faunas

Abstract: Ecological diversity provides a means of analysing the community structure of fossil mammalian faunas in order to obtain information on the habitat of the fauna. As a basis for the analysis, 23 modern mammalian communities from distinct habitats have been used to establish patterns of community structure for tropical African habitats according to their species diversity by taxonomic group, size, locomotor zonal adaptation, and feeding adaptation. All the communities tested were in tropical Africa, but additional analyses on tropical forest communities in Australia, Malaya, and Panama have shown that these communities, which all have completely different species composition, nevertheless have community structures very similar to each other and to those of the African forest communities.

The ilio‐sacral articulation in frogs: form and function

Abstract: The amphibian order Anura (frogs) is a major group whose origin appears related to the transformation of its locomotor system for saltation. However, the ilio-sacral articulation, a uniquely specialized part of the frog locomotor morphology, remains largely unstudied. Preliminary work reveals significant differences in the morphology of the ilio-sacral articulation among extant frogs and suggests that differences in types of articulation are correlated with different directional movements at the joint, with specific locomotor modes, and wim phylogenetic groupings. SUMMARY The morphology of the ilio-sacral articulation in frogs is correlated with different patterns of mobility at the joint and different locomotor behaviors. Overlain on diese basic differences in articulation among frogs is variation in other aspects of pelvic and vertebral morphology as well: muscle origin and insertion, urostyle fused or free, length and angle of the ilia, length of transverse processes of the pre-sacral vertebrae, and die articulation pattern of die presacral vertebrae. Obviously, the role of these additional morphologies must be established and integrated with the data on articular morphology before die form-function complex is completely understood. This paper is the first step towards that end, and work on other aspects of pelvic and vertebral morphology is underway.

The evolution of insect/vertebrate associations

Abstract: The evolution of close vertebrate associations has occurred in seven orders of insects, resulting in a great diversity of interactions which range from commensalism to true parasitism. The evolution of each taxon of vertebrate associates is discussed in turn, some new ideas on the development of certain groups are presented and, on a broader scale, a general model for the evolution of ectoparasitic insects is proposed. It argues that all vertebrate associates have evolved along one of two macroevolutionary pathways which differ only in the sequencing of adaptations facilitating host association and host feeding. These pathways lead to parasite types which differ greatly in their life history and intimacy of host association. Some microevolutionary processes influencing the diversification of ectoparasites are discussed, in particular the process of insect/vertebrate coevolution and the forms this may take. Host specificity, one consequence of coevolution, is recognised as an important factor influencing the structure of ectoparasite communities, and a hypothesis is presented that competition between ectoparasite species, mediated by host defensive responses, is also important in determining community structure.

Evolution of the tetrapod ear: an analysis and reinterpretation

Abstract: The dominant view of tetrapod otic evolution–the “standard view”–holds that the tympanum developed very early in tetrapod history and is homologous in all tetrapods and that the opercular process of the rhipidistian hyomandibula is homologous to the tympanic process of the stapes in lower tetrapods. Under that view, the labyrinthodont amphibians of the Paleozoic are usually considered ancestral to reptiles, and thus the “otic notch” of labyrinthodonts and the tympanum it presumably contained form the starting-point for middle ear evolution in reptiles. Four problems have classically been identified with the standard view: the differing relationships of the internal mandibular branch of N. VII (chorda tympani) to the processes of the stapes in amniotes and anurans; the differing orientations of the stapes in key fossil and living groups; the location of the tympanum in early fossil reptiles; and the transferral of the tympanum, during the origin of mammals, from the stapes to the articular bone of the lower jaw. An examination of these problems and of the solutions proposed under the standard view reveals the ad hoc, and therefore unsatisfactory, nature of the proposed solutions. To organize and review alternative hypotheses of otic evolution an analytical table is constructed, using three characters (tympanic process, Nerve VII, tympanum), each with two possible states. A total of eight hypotheses about middle ear evolution are possible under this system, one of which is the standard view. The seven “non-standard” hypotheses, only five of which have been argued in the literature, are briefly examined. Six of the “non-standard” hypotheses appear unattractive for various reasons, including reliance on ad hoc arguments. The seventh was first proposed by Gaupp in 1898. It is today almost universally ignored but apparently largely for historical rather than scientific reasons. This hypothesis, her called the “alternative view”, appears to rest on assumptions equally as plausible as those of the standard view. Moreover, it offers a solution of the problems associated with the standard view without, apparently, raising any similarly serious problems. This paper compares the standard and alternative views of middle ear evolution in detail. Comparison proceeds on two levels. On one level, they are compared in terms of the hypotheses of phyletic tetrapod relationships each promotes and how strongly each supports its hypothesis. Both views promote the same hypothesis of tetrapod relationships. The alternative view is the more parsimonious, but the difference is not considered sufficient to provide a choice. On another level, the two views are compared in terms of their implications for: (1) the evolution of relative and absolute auditory perceptive ability; (2) the origin of reptiles; (3) the evolution of the suspensorium and cranial kinesis; and (4) the origin and evolution of recent amphibians. The nature of the data required for a test of the implications of the two views is specified in each case. Where data are available. the alternative view is consistent and the standard view is inconsistent with these data. We conclude that the alternative view is the preferable hypothesis of middle-ear evolution. This conclusion implies the following: the tympanic membranes and the tympanic processes of the stapes in recent mammals, reptiles + birds. and frogs. are not homologous; the evolution of “special periotic systems” in the ancestors of amphibians and amniotes were independent events and preceded the evolution of tympanic membranes; the amphibian tympanic membrane. probably including that of labyrinthodonts. is not ancestral to that of amniotes. and that labyiinthodonts with an otic notch are not suitable as amniote ancestors; the stapes of early reptiles functioned primarily as part of the jaw suspension rather than in hearing; the mechanisms and abilities of sound perception in recent tetrapods are likely to be diverse rather than forming parts of a cline; and the lack of a tympanum in Gymnophiona and Caudata may be a retention of a primitive condition.

Pyrrolizidine alkaloids in arctiid moths (Lep.) with a discussion on host plant relationships and the role of these secondary plant substances in the Arctiidae

Abstract: Pyrrolizidine alkaloids (PA) have been identified in six species of Arctiidae reared on Senecio and Crotalaria. These include senecionine, seneciphylline, integerrimine, jacobine, jacozine, jacoline, jaconine and a metabolite (C15H25NO5) from Senecio, and monocrotaline, trichodesmine and crispatine from Crotalaria. The all-red aberration of Tyria jacobaeae (var. conyi) contained much less of the metabolite than normal examples of this species. Female Spilosoma lutea reared on the same plants of S. jacobaea contained markedly more jacobine and jacoline than die males. Host plant relationships and secondary plant substances are discussed. It is suggested that the Arctiid moths' own deterrent secretions, directed against vertebrate predators, pre-adapts them for feeding on foliage likewise protected against large herbivores by toxic secondary plant substances such as cardenolides and pyrrolizidine alkaloids. These latter substances are more toxic to vertebrate than to insect herbivores, and their dual function of deterrent and insect aphrodisiac puts a premium on their sequestration and storage once a species has achieved the initial steps, and occupied the plant niche concerned. It is further suggested that the polyphagous habits of the Arctiidae result in a more equitable distribution of die secondary plant substances within the Mullerian complex concerned, thus providing a generalized warning message for the potential vertebrate predator.

A comparative study of the buccal pumping mechanism of tadpoles

Abstract: To understand the ecological significance of diversity in the buccal pump morphology of anuran larvae we have developed a descriptive geometric model of the tadpole buccal pump The model allows comparison of the buccal puinping mechanism of different species The reliability of the model was established by comparing buccal volumes predicted by the model with buccal volumes reported in the literature for Rana sylvatica and Rana catesbeiana as well as those obtained from our own feeding experiments with Xenopus laevis larvae The model was used to examine the following features for the larvae of 40 species from 11 anuran families: (1) the amount of deflection in the buccal floor with each stroke of the buccal pump (angle of rotation of the ceratohyal); (2) the mechanical advantage of the pump (the relative length of the lever arm on the ceratohyal); and (3) buccal volume We identify patterns in diese three features that correlate with the feeding ecology of a variety of tadpoles Macrophagous larvae tend to have a long lateral lever arm on the ceratohyal (high mechanical advantage), and produce a large buccal volume by deflecting a large buccal floor area through a shallow arc (ie a large bore, short stroke system) Midwater, microphagous larvae tend to have poor mechanical advantage, but nevertheless achieve a large buccal volume; in these forms the large buccal volume is obtained by deflecting a smaller buccal floor area through a larger arc (ie a small bore, long stroke system) Benthic larvae, such as stream tbrms with suctorial mouths, tend to have high mechanical advantage, but only modest buccal volume Larvae can regulate their feeding rate by varying either the p umping rate (frequency modulation) or the buccal floor displacement (amplitude modulation) The anatomy of the buccal pump may determine not only the feeding ecology of a larva, but the predominant behavioral pattern it uses to regulate its feeding rate Buccal volume has a negative allometric relationship to body length both intraspecifically and interspecihcally

Stability and variation in aphid clonal lineages

Abstract: Evidence in the literature purporting to show genetic variability within parthenogenetic lines of aphids is reviewed. The results of three experimental approaches to this problem are reported: (1) a long term study of fluctuation in alate morph production in six lines of Myzus persicae; (2) an attempt tp select for caudal hair form in Acyrthosiphon pisum; (3) a study of the inheritance of esterase variants of M. persicae in sexual and parthenogenetic reproduction. It is concluded that genetic recombination during parthenogenesis is not the general rule in diese aphids, and that aphid parthenogenesis should be regarded as of ameiotic or apomictic type. Possible alternative explanations for the different kinds of variation or apparent variation which occur within aphid clonal lineages are discussed.

Phylogenetic analysis and classification of fossil and recent Alcelaphini Mammalia: Bovidae

Abstract: Cladistic principles are applied to a group of antelope species, three-quarters of which are extinct. Only cranial and mandibular characters are used. The present phylogenetic hypothesis suggests diat the Alcelaphini are monophyletic; that the genera Parmularius and Damaliscus share a recent common ancestry; and that die extant Hunter's hartebeest should not be removed from Damaliscus into a separate genus Beatragus as several authors have done. A re-evaluation is suggested of die systematic position of Lichtenstein's hartebeest, as being phylogenetically closer to me wildebeests, genus Connochaetes, than to the type species of the hartebeest genus Alcelaphus. Some problems arising in the application of cladistic principles to such a low ranking group, treating die fossil majority exactly equivalently with recent taxa, are discussed. Comments on recency of common ancestry as it affects hybridization potential in bovids, on speciation and extinction rates arise.

Enzyme variation and taxonomy: the estimation of sampling errors in measurements of interspecific genetic similarity

Abstract: The uses of biochemical genetics as an aid to taxonomy are discussed briefly. A survey is made of published data to establish expected levels of genetic similarity or identity between conspecific populations, between congeneric species and between species of different genera. Existing measures of genetic similarity, identity or distance are discussed and some of the difficulties involved in their use in taxonomy are outlined. A new measure of genetic similarity is proposed specifically designed for use in making interspecific comparisons for taxonomic purposes. This measure offers considerable advantages in ease of calculation and also greatly simplifies the estimation of sampling errors. An empirical comparison is made, using published data, of the measures and confidence limits obtained by the proposed memod against published measures of genetic variation between species.

Sympatric speciation: a simulation model

Abstract: A model of mating and population growth dependent on competition that suggests circumstances under which sympatric speciation might occur is described. The model is similar to one in a companion paper by Rosenzweig in that a heterozygote genotype, involving a new allele, is first selected by virtue of its ability to exploit a new niche and is then eliminated through competition. The superior competitor, which eliminates the heterozygote, is the homozygote for the new allele. For this process to occur the heterozygote must be sufficiently fit to exploit and invade a new niche, but not so fit that a classical polymorphism results from heterozygous advantage. This process of speciation is most likely to occur when there are vacant niches. When and where these might occur are discussed.

The species of Hymenoptera described by Linnaeus in the genera Sphex, Chrysis, Vespa, Apis and Mutilla

Abstract: Data are presented on the type-material representing the species described by Linnaeus in his genera Sphex, Chrysis, Vespa, Apis and Mutilla, The names here considered total 158; six are currently applied in the Hymenoptera Parasitica. Of the balance of 147, three are emendations and five are unavailable homonyms or names proposed in the synonymy of other species. Fifteen Linnaean names are here placed as synonyms. One name is attributed to an author other than Linnaeus, and live names remain species incertae sedis. The remainder, 118, are applied as valid names in die Hymenoptera Aculeata. Holotype specimens in London, Uppsala or Stockholm represent 60 names; 55 names are based on lectotype specimens of which 49 are here designated, two by other authors. One name is represented by a neotype specimen in Lund, and one by a lectotype figure. One non-aculeate species is based on syntypes. Specimens appear to be lost with respect to 25 names; three specimens in Uppsala may be the holotypes of a further three species. Eight new combinations are made, and twelve new synonyms established; three further new combinations and three further new synonymies are suggested. A systematically arranged summary of species treated and of nomenclatural changes made is given. Nomenclatural changes affecting non-Linnaean names are included where relevant; lectotypes are designated for two non-Linnaean species.

Ecological and taxonomic trends in macrolepidopteran host plant selection

Abstract: Patterns of host plant use by larvae of macrolepidoptera feeding on trees and shrubs in Britain and Canada are examined. The incidence of polyphagous species varies among different lepidopteran taxa. Among largely monophagous taxa host plant switching has often occurred. The greater similarity of insect faunas on closely related plants is documented using cluster analysis. The Canadian data reveal that lepidopterans feeding on conifers are less specific in their host plant choice than species feeding on angiosperms. The numerical analyses also provide evidence of greater overlap in the insect faunas of plants belonging to the same ecological association. These results are discussed with particular reference to Lepidoptera-plant coevolution.

Ecological and morphological variation of Canary Island blue tits, Parus caeruleus (Aves: Paridae)

Abstract: Canary Island blue tits have differentiated within the last million years. Compared with mainland populations they have short wings, large beaks and tarsi, and tend to be less variable in these parameters. Within the archipelago the eastern populations have the shortest wings and tarsi but the widest and deepest beaks. The eastern populations may have been derived from central island ones, following extinction of the original eastern populations during a warm period in the last Ice Age. New measurements have been used to test contrasting predictions of hypotheses that explain inter-island morphological variation in terms of either climatic or ecological influences. Neither hypothesis is sufficient to explain the variation. A model which combines mem is proposed as follows. Mild winter temperatures have selected for small body size and wing length, especially on the hot, dry, eastern islands. On the other pine-forested, islands, selection has favoured relatively long tarsi and long, slender, beaks for efficient foraging among pine foliage. The absence of die pine-dwelling coal tit from the islands has facilitated mis evolutionary shift. It is shown that blue tits in pines forage more in the needles and cones on the Canary Islands than they do on die North African mainland.

Will Great Tits become Little Tits

Abstract: The mean size of Great Tits Parus major in our study at Ghent shows a significant decreasing trend in the period 1962 to 1975. Since it has been shown that in the Great Tit the heritability of tarsus length, a measure for size, is rather high, we believe the observed trend to be a directional micro-evolutionary change. After investigating several possible causes for the size decrease, we suggest that the observed change is caused by a shift in the equilibrium between selective pressures favouring large and small individuals. Before our study, breeding numbers of Great Tits were limited through the lack of suitable nest-sites. We think that more of the large males could reproduce in mat situation. When we provided nestboxes in surplus this selective pressure was relaxed, and since small females must produce more surviving offspring, this further shifts the balance. We argue that during the evolutionary history of the Great Tit there was no lack of suitable nest-sites in natural habitats, that by providing nest boxes we restore the natural situation, and diat therefore the decrease in size should level off.

The calculating cormorants

Abstract: Traditional fishing with captive cormorants was observed on the Li-Kiang River. After catching seven fish the birds were allowed to eat the eighth. Without this reward they refused to fish again. These birds could apparently count up to seven.

Why do adult insects not moult

Abstract: Hypotheses are presented concerning why mayflies moult after functional wings develop and why most insects cease to moult at this time. The pattern of retention or loss of the subimaginal moult in extant mayflies suggests that this moult may be necessary to complete elongation of caudal filaments and forelegs of adults. It is then analogous to the pupal moult of holometabolous insects. I propose that selection for wing efficiency has normally confined the presence of functional wings to one instar only, which is also the last and reproductive stage. Selection for light wings has generally caused the epidermis of membranous insect wings to degenerate, thereby precluding otherwise advantageous adult moults.

Towards a theory of the evolution of butterfly colour patterns under directional and disruptive selection

Abstract: Two general models for the transspecific evolution of butterfly colour patterns are advanced: directional selection acting equally on both sexes, and disruptive selection involving periods of polymorphism. To consider possible outcomes of me latter process, a morphism notation based on an integrated classification for polymorphism and sexual dimorphism is developed. This notation is used to examine the properties of all morphism transformations possible from the minimal expressions of the nine morphism categories, as reached through defined minimum step changes. The significance of such pathway models is analysed in terms of general properties of butterfly polymorphism. The potential use of pathway models in evolutionary studies is briefly discussed, mainly with respect to phylogenetics, and ideas on the evolution of genetic dominance.

Food overlap in co-existing populations of the land snails Cepaea nemoralis (L.) and Cepaea hortensis (Müll)

Abstract: Faecal analysis of adult Cepaea nemoralis and Cepaea hortensis from a mixed population on chalk grassland shows that the two snail species select the same plant material as food. Herbs are selected in preference to grasses and Urtica dioica is particularly favoured. C. hortensis has the more pronounced preference for senescent material. These results are discussed in relation to competition between the two species.

The freshwater Crustacea of the island of Rhum (Inner Hebrides) – a faunistic and ecological survey

Abstract: A survey of the freshwater crustacean fauna of the island of Rhum (Inner Hebrides) revealed at least 68 species. Information is provided on die distribution and ecology of these, and individual preferences are noted. These preferences lead to assemblages found in habitats whose ecological attributes can be related to geological, edaphic and chemical features of the environment. While species diversity on the island as a whole is perhaps greater than might have been anticipated, that of individual water bodies tends to be low, the maximum number ol species in any one water body being 2 7. The fauna includes a sizeable element of species that favour acidic waters of various kinds or oligotropliic/dystrophic lakes and pools of low ionic content, and includes a number of northern or burco-Alpine species. The origin of this isolated fauna is briefly considered.

Why change mates

Abstract: In some wading birds (Charadrii) each adult rears a brood alone. The female leaves her first clutch with her first mate before herself rearing a clutch fertilized by a second male, who is already tending its first mate's first clutch. We here develop a simple model to account for the exchange of mates between clutches, and relate it to reported field studies. We suggest that females are attempting to be polygamous, rather than simply bigamous. Provided a female has a chance of obtaining a second, unmated male and that the costs of leaving the first male before remating are not high, matechanging will be favoured over monogamy. The implications of this model to the evolution of the more usual forms of polyandry and of male-like females are discussed.

The evolution and distribution of Calyptozetes sarekensis (Acari: Oribatei)

Abstract: Calyptozetes sarekensis, an oribatid mite found predominantly, though not exclusively in lichens, inhabits regions within the arctic circle and subarctically between latitudes 60o and 70o (Swedish Lapland, Norway, Bear Island, Spitzbergen, Jan Mayen, Iceland, Greenland, northern Canada). In recent years, however, the species has been recorded from a number of montane sites in Great Britain and southern Europe. There would appear to be only two possible explanations for die discontinuous distribution of this mite. (1) The species has been transported from its main arctic and subarctic area of distribution to its southern montane outposts by some agent (driftwood, birds, wind), or (2) in Britain and southern Europe it represents a relict species of the Ice Age, left stranded on high ground after the final retreat of the ice. Evidence is presented in support of the second hypothesis. In addition, it is suggested that its presence on the different land masses of its main arctic and subarctic range, which are separated from each other by wide stretches of ocean, could be explained by die hypothesis that it is a very ancient species daring from the time Laurasia was in existence some 60 or more million years ago. The alternative hypothesis of transportation of the species between one or more of these areas, however, is by no means ruled out.

Hybridization studies in the Schistocerca americana complex. I. The specific status of the Central American Locust

Abstract: The Central American Locust has previously been identified as Schistocerca paranensis (Burmeister), the Argentinian Locust, and it has been suggested that S. americana of North America represents its solitarious phase. Hybrids of locusts from the Yucatan peninsula of Mexico with locusts from Argentina and Florida were reared, their fertility measured and meiosis in the males examined. It was found that: (1) sex ratios in the F, hybrids were distorted; (2) hybrids had reduced fertility; (3) female hybrids were more fertile than male hybrids; (4) meiosis in hybrid males was disturbed; (5) these effects were more pronounced in die hybrids with the Argentinian Locust than in those with Florida locusts. These results are discussed in relation to Haldane's rule and the biogeography of die group. It is concluded that the Central American and Argentinian Locusts are separate species, but that the relationship of the former to S. americana americana requires further investigation.

Macroevolution — myth or reality ?

Abstract: Current concepts of macroevolution–the origin and diversification of higher taxonomic categories-are reviewed. A reductionist hypothesis, seen in the light of models based on extant species, seems to be corroborated. There appears to be no reason to think that macroevolution is a natural phenomenon distinct from a speciation event giving rise to a new phyletic lineage. Neidier is it necessary to postulate any quantum element in that speciation event.

Nontoxic toxins: the energetics of coevolution

Abstract: I propose that the relative productivity of an organism in its community importantly influences the kinds of predator defences that are most effective relative to their costs Two classes of defence mechanisms are distinguished: those that give some energy to the predator (tribute defences) and those that do not (non-tribute defences) The pattern of distribution of these two types of defences both geographically and among different taxonomic groups of organisms support the hypothesis that the productivity of a species relative to others in its community is an important determinant of the type ol defence a species adopts

Character selection in relation to the numerical taxonomy of some male Diaspididae (Homoptera: Coccoidea)

Abstract: A quantitative comparison of the classifications of 24 species of male Diaspididae by principal component and principal coordinate analysis was extended to allow the comparison of classifications based on selected subsets of the 101 available characters. It was shown that subsets of 25–28 characters could be chosen numerically and used to construct classifications that resembled very closely the classification based on the reference set of characters. The conclusions are discussed in relation to other views on character-weighting and in relation to classifications of the Diaspididae based on traditional taxonomic characters provided by the females.

Home range and movement in populations of Rattus norvegicus polymorphic for warfarin resistance

Abstract: Movements of brown rats were deduced from records made during a capture-recapture study of rural populations on two farms in Mid-Wales. Populations in the hedges were sampled at monthly intervals for two years, but samples from the farm buildings were obtained only irregularly and by a variety of methods. On the main trap line, of the rats captured during at least two sampling periods 35 (78%) females and 57 (74%) males appeared to have established home ranges, the best estimates of mean home range length for each sex being 54.8 m and 66.1 m respectively. The longest recorded distances travelled during known life were 850 m for a female and 954 m for a male, although the median distances travelled were only 43 m and 52 m respectively. The median distance travelled during a sampling period (seven nights) was about 24 m for both sexes. There were no significant differences between the distances travelled by the sexes or by different age groups, and there was little seasonal variation. Infestations in the hedges were always associated with streams, and those more than about 100 m from the buildings seldom persisted through winter. During autumn and winter the rats in the more distant localities tended to move towards the buildings, but there was no suggestion of an orderly migration. Twenty-seven out of 386 rats marked in the hedges were recovered amongst 576 taken from the buildings, but only nine of diem had travelled more than 100 m. No rats released in the buildings were captured in the hedges. Rats established in the buildings seemed to exclude rats immigrating from the hedges.

The ecology of two West Indian species of mud‐wasps (Eumenidae: Hymenoptera)

Abstract: Factors affecting the distribution and numbers of the neotropical mud-wasps Zeta abdominale (Drury) in Jamaica and Z. canaliculatum (Oliv.) in Trinidad are discussed. Rainfall was a limiting factor in both aspects of the ecology of the two species. In Jamaica, Z. abdominale was virtually absent from rainfall zones >2540 mm m.a.p. (mean annual precipitation), whereas in Trinidad, Z. canaliculatum hardly inhabited those localities of > 2250 mm m.a.p. Furthermore, the local populations were progressively smaller and more scattered in wetter areas, because consistent rainfall and overcast conditions may result in reduced nesting activity. However, in a favourable locality, numbers may be temporarily increased after rainfall which boosts food supply (caterpillars). Developmental mortality, at 57.68% and 57.2896 respectively was remarkably similar in Z. abdominale and Z. canaliculatum. The important predators within the cells were Melittobia sp. (hawaiiensis complex) (Eulophidae) and Amobia fioridensis Townsend (Miltogramminae). In Zeta abdominale total developmental mortality was positively correlated with log,0 (no. of cells) at different sites; averaging only 33.3% for small populations, but 77.4% for large ones. Regulation at low numbers (Z. abdominale) was probably achieved by harsh physical factors, causing low fecundity, but great survival in the cells and high emigration rate. Where Z. abdominale was numerous, the physical environment was favourable, but developmental mortality was so high, that it is necessary to postulate the immigration of many nesting females.

Lateral asymmetry of kidney weights in different populations of wild mice

Abstract: Weights of right and left kidneys were compared in different populations of wild mice. Samples were taken from Great Britain, Pacific islands and Sub-Antarctica. The different population samples were further subdivided according to sex and age as estimated by tooth category (i.e., degree of development or wear of upper molars). The mean weights of right kidneys exceeded those on the left in all 28 Subsamples but the data suggested mat this difference decreased with age. The evidence further suggested that the asymmetry between the two kidneys was greater in populations of small mice from the Pacific islands than in those of large mice from Britain and Sub-Antarctica. On the basis of published data on rats and guinea pigs the question is raised whether interspecific differences in kidney asymmetry may be explicable by differences in the sizes of the kidneys in different species.