Species Of Similar Size Research Articles

Vertical stratification of small mammals in the Atlantic rain forest of south-eastern Brazil

Patterns of vertical stratification and canopy utilization by rodents and marsupials were analysed in two contiguous Atlantic forests at different altitudes (100 m and 900 m asl). Twenty-two species were captured using live traps placed at ground level, in the understorey (1.5–2.0 m), and in the canopy (6–15 m) over 2 y; seven species (32%) were mainly or exclusively arboreal. Community composition and relative abundance of species in the different vertical strata were not similar, with a general reduction in the number of species, and in abundance in the upper layers. The following species were captured mainly or exclusively in the canopy: Micoureus demerarae and Gracilinanus microtarsus (Didelphimorphia, Didelphidae); Wilfredomys pictipes , Oecomys aff. concolor , and Rhipidomys aff. macrurus (Rodentia, Muridae); and Nelomys nigrispinus (Rodentia, Echimyidae). Our results indicated that altitudinal changes in Atlantic forest areas may alter the community composition of different forest layers but they do not seem to alter greatly specific patterns of vertical habitat utilization. Similar-sized species tended to differ in their patterns of vertical utilization of habitat with the exception of terrestrial akodontine rodents (genera Akodon , Thaptomys , Oxymycterus and Brucepattersonius ). Rodents (mainly Oryzomys russatus ) dominated captures at ground level at both sites but Akodontinii were numerous only at the highest site. Unlike other neotropical forests, marsupials did not dominate canopy captures.

Ontogenetic allometry in the locomotor skeleton of specialized half‐bounding mammals

AbstractSpecialization for a locomotor behaviour may affect limb bone morphology throughout ontogeny. Ontogenetic development of the limb skeletons of two mammalian species, which are behaviourally specialized for the half‐bounding gait (Chinchilla lanigera and Oryctolagus cuniculus), were compared to two similarly‐sized species which are not specialized for half‐bounding (Rattus norvegicus and Monodelphis domestica). Limb bone lengths and anteroposterior diameters (mediolateral diameters for the radius and metacarpal) were measured from radiographs taken throughout the ontogeny of each species. Body mass was also measured repeatedly during growth. Bone measurements were regressed against body mass, as well as forelimb bone length vs serially homologous hindlimb bone length, bone length vs total limb length and bone length vs width. Similar comparisons were made among adults of each species using ratios. Although there were many significant differences among species, overall there were few consistent differences in adult scaling ratios or ontogenetic allometry slopes between specialized and generalized groups. Adult specialized half‐bounders had significantly narrower tibiae and metatarsals than the gait‐generalized runners. Specialized half‐bounders usually had similar slopes for hindlimb length vs width ontogenetic comparisons, but the non‐specialized species did not group together. However, there were two patterns that occurred among all four species: (1) hindlimb bone lengths nearly always grew faster than the serially homologous forelimb bone lengths in all species; (2) proximal elements usually increased in length proportionally faster than distal elements. In conclusion, small mammals may share strong developmental constraints that govern their relative growth rates. It is also likely that there are different selective pressures on juveniles and adults, but that these selective pressures may not be different between specialized and unspecialized runners during ontogeny.

Bobcat Killed by a Coyote

Coyotes (Canis latrans) and bobcats (Lynx rufus) are often killed by larger carnivores, including wolves (Canis lupus) and cougars (Felis concolor) (Koehler and Hornocker, 1991; Peterson, 1995). Although interspecific strife between coyotes and bobcats has been inferred (Litvaitis and Harrison, 1989), there are few documented instances of aggressive behavior between these 2 similarly-sized species. Here, we describe characteristics of an adult female

Azteca Ants as Antiherbivore Agents of Tococa formicaria (Melastomataceae) in Brazilian Cerrado

Several ant species have been found associated with domatia of plant species of the genus Tococa (Melastomataceae). In the present study we investigated the relationships between Tococa formicaria Mart. and ants in the Cerrado (savanna-like vegetation) from central Brazil. We addressed questions about the utilisation of domatia by different ant species and their efficiency in reducing herbivory. We found 8 ant species in the domatia, with Azteca sp. 1 being present in 47.2% of the sampled individuals. The other species found were: Azteca sp. 2, Camponotus sp., Dolichoderus gr. diversus, Dolichoderus lutosus, Leptothorax sp., Oligomyrmex sp. and Linepithema sp. The dominance of Azteca sp. 1 was significantly higher in the larger individuals, with about 85% of individuals in the highest size class being occupied by this species. We performed experiments of attack to live baits (termites) on T. formicaria leaves and on leaves of control species (any other neighbouring plant species of similar size). The recruitment rates were significantly higher on T. formicaria leaves. We also showed that herbivory was significantly lower in T. formicaria individuals occupied by Azteca sp. 1 than in individuals occupied by other ant species. The results of this study may be considered as evidence to support the assumption of a mutualistic relationship through defence against herbivory between Azteca ants and T. formicaria.

Diversity and abundance of vascular epiphytes: a comparison of secondary vegetation and primary montane rain forest in the Venezuelan Andes

Species diversity of vascular epiphyte plant communities was studied in La Carbonera, a montane rain forest dominated by Podocarpaceae in the Venezuelan Andes. We compared the epiphyte communities of the primary, disturbed, and secondary forest areas of La Carbonera in order to augment the scarce knowledge on the effects of anthropogenic disturbance on these important elements of tropical vegetation. Diversity of vascular epiphytes (191 species in the whole forest area) was low in the disturbed and secondary areas (81 spp.) compared to adjacent primary forest (178 spp.). Four types of disturbed forest and secondary vegetation supported different numbers of epiphyte species, showing a decline with increasing degrees of disturbance (65 spp. along a road transect, 42 spp. on relict trees in disturbed forest, 13 spp. in a tree plantation and 7 spp. in a former clearing, both secondary vegetation units). Epiphytic species composition in primary and disturbed or secondary forest areas differed markedly: disturbed habitats harboured fewer fern and orchid species but more bromeliad species than the primary forest. Probably the families occurring only in primary forest sites of our study may be useful as bioindicators to determine the degree of disturbance in other habitats of mountain rain forests as well. Epiphyte abundance was also lower in disturbed habitats: a remnant emergent tree supported only about half as many epiphyte individuals as a member of the same species of similar size in the primary forest. The decrease in species numbers and abundance as well as the differences in species composition are mainly due to the less diverse phorophyte structure and less differentiated microclimate in the disturbed and secondary vegetation compared to the primary forest.

Partitioning of Habitat and Prey by Abundant and Similar-sized Species of the Triglidae and Pempherididae (Teleostei) in coastal waters

The aim of this study was to determine whether certain co-occurring and abundant species of the teleost families Triglidae and Pempherididae are segregated spatially and/or by diet, and are thus less likely to be susceptible to competition for resources. Nocturnal otter trawling in shallow (5–15m) and deeper (20–35m) waters in four regions along ∼200km of the south-western Australian coastline collected large numbers of a wide size range of the triglidsLepidotrigla modestaandLepidotrigla papilioand the pempherididsPempheris klunzingeriandParapriacanthus elongatus. Although these four species frequently co-occurred at several sites, each species attained its highest density at different sites, thereby representing a partial segregation of these species by habitat. This even occurred with the congeneric triglid species, withL. modestabeing most abundant in the four deep, offshore sites, whileL. papiliowas most numerous at three sites which varied in depth and distance from shore. Although triglids and pempheridids both consumed substantial amounts of amphipods and mysids, only the members of the latter family ingested a large amount of errant polychaetes. The latter difference is assumed to reflect the fact that, in comparison with triglids, pempheridids can swim faster, have a mouth adapted for feeding upwards in the water column and feed at night when errant polychaetes emerge from the substratum. Although the dietary compositions ofL. modestaandL. papiliodid not differ significantly when analyses were based on dietary data for all sites, they did differ significantly when analyses were restricted to dietary data obtained when both species were abundant and co-occurred. The likelihood of competition for food is thus reduced in the latter circumstances. In comparison withP. klunzingeri,P. elongatusconsumed a relatively larger volume of amphipods and a relatively smaller volume of mysids, which are more mobile, implying thatP. elongatusfeeds to a greater extent on rather than above the substratum surface. The diets of all species underwent ontogenetic changes, which were particularly marked inP. klunzingeriwhere an increase in body size was accompanied by a reduced consumption of mysids and an increased ingestion of errant polychaetes and amphipods. The fact thatL. modesta,L. papilio,P. klunzingeriandP. elongatusare partially segregated by habitat and feed on suites of prey which differ in composition, allied with an interfamilial difference in the time of feeding, would reduce the likelihood of competition for resources amongst these four species, when they co-occur and are abundant. Furthermore, ontogenetic changes in diet would reduce the potential for intraspecific competition for food.

Characterization of excised DNA intermediates associated with V(D)J recombination at the T-cell receptor delta locus.

Lymphocyte development requires the assembly of antigen receptor genes through the specialized process of V(D)J recombination. This process is initiated by cleavage at the junction between coding segments (V, D, and J) and the recombination signal sequences that border these segments, resulting in generation of double-strand break intermediates. We have used a two-dimensional gel system to characterize broken molecules arising from V(D)J recombination at the T-cell receptor (TCR) delta locus and have identified linear species excised by Ddelta1-Ddelta2 and V-Ddelta2 rearrangement in thymus DNA. Relatively few (approximately 10) V-Ddelta2-excised linear species were detected in DNA from fetal thymocytes. The sizes of these species corresponded to the estimated distances between Ddelta2 and the V gene segments utilized by gammadelta T cells and indicated that both Ddelta2-proximal and -distal V gene segments are targeted for V-Ddelta2 rearrangement. Similar-sized species were observed in DNA from thymocytes of scid mice in which T-cell development is arrested prior to TCR expression. Since previous studies suggest that the TCR alpha/delta locus encodes more than 100 V gene segments, our results indicate that a few select V gene segments are predominantly targeted for rearrangement to Ddelta2, and this primarily accounts for the restricted Vdelta gene repertoire of gammadelta T cells.

Crown Construction, Leaf Dynamics, and Carbon Gain in Two Perennials with Contrasting Architecture

We used two co—occurring plant species of similar size and leaf morphology but with contrasting architecture to test if they would show specific patterns of leaf demography and leaf ecophysiology when they were grown in a range of experimental environments. Aster lanceolatus, a species with branched shoots, had exponentially increasing leaf populations. This led to high leaf turnover rates and to crowding of leaves at the top of the plants. Solidago canadensis, a species with unbranched shoots and rapid height growth, had linearly increasing populations of leaves, leading to a uniform vertical distribution of leaves and to lower leaf turnover rates. In comparison with the short—lived leaves of A. lanceolatus, the leaves of S. canadensis lived longer, contained more nitrogen and calcium per dry mass, and responded to changing light conditions within the plant crown by adjusting their angles towards the sun. Leaves of A. lanceolatus had an early peak in gas exchange activity followed by a rapid decline, whereas gas exchange activity in leaves of S. canadensis at the beginning of leaf development was lower than in A. lanceolatus but decreased only slightly with leaf age. Within the narrow vertical band in which leaves of A. lanceolatus were concentrated, young leaves at the top had higher mass per area, higher chlorophyll a/b ratios, and much higher rates of photosynthesis and conductance than the older leaves beneath. In S. canadensis, in which leaves were distributed over much of the vertical dimension along the plant, upper leaves, in contrast to lower (older) leaves, had lower mass per area, were held less perpendicular to the sun, and had higher rates of photosynthesis in high but not in low light. Because leaf populations grew exponentially in A. lanceolatus, assimilates could be re—invested; thus leaf number during the second half of the growing season was a good predictor of final biomass. In S. canadensis, with linearly growing leaf populations, the assimilates that were not re—invested in new leaves were allocated to the stem, and stem height or volume were good predictors of final biomass. Compared with the strong influence of architecture on the structure and dynamics of leaf populations, the effects of background species and fertilizer application were weak but nevertheless significant. Background species of similar aboveground mass but different stature (the tall Solidago altissima and the short Poa pratensis) affected leaf deployment (internode elongation, leaf orientation, and leaf survival), probably via competition for light, but not leaf quality (morphology, physiology) of the two target species A. lanceolatus and S. canadensis. Further, diameter—height allometries, which varied considerably among plants, tended to be flatter if the target species were grown in the tall than in the short background. Fertilizer application accelerated plant growth and phenological development. It increased light competition among leaves and leaf turnover; nevertheless, the photosynthetic water use efficiency of old leaves was higher in fertilized than in unfertilized plants. We suggest that the characteristic leaf dynamics of A. lanceolatus and S. canadensis are typical for the contrasting aboveground architectures these species represent. Based on the results of this and previous studies we suggest that an important driving force in the evolution of these complex adaptations is the degree of mixing within canopies of leaves of different plant genotypes. Leaves (and branches) are expected to be more autonomous if they frequently interact with leaves from other genotypes, as in the polyclonal patches of A. lanceolatus with its long and intermingling belowground rhizomes, than if they usually interact with leaves from the same genotype, as in the monoclonal patches of S. canadensis with its short rhizomes and compact belowground architecture.

Energy Reserve Lipids of Zooplanktonic Crustaceans from an Oligotrophic Saline Lake In Relation to Food Resources and Temperature

In three zooplankton species examined over a 2-yr period in an oligotrophic saline (22 g∙L−1) lake, triacylglycerols (energy reserve lipids) were the most abundant lipid class followed by phospholipids and sterols. Marked seasonal differences in patterns of total and energy reserve lipid content in the herbivorous calanoid Leptodiaptomus sicilis were correlated with temporal patterns in edible algal biomass and temperature. The appearance of particular algal species, or groups of similar-sized species, occurred synchronously with changes in lipid content of both L. sicilis and Daphnia pulex. These periods of changing lipid content were used to infer nutritional suitability or inadequacy (unavailability) of specific algae for wild populations of zooplankton. Energy transfer from phytoplankton to the carnivorous calanoid Hesperodiaptomus nevadensis through L. sicilis involved a time lag of approximately 1–2 mo; this was hypothesized to result from a feeding dependency on L. sicilis copepodites due to a gape limitation of the predator. Demographics of D. pulex in this lake were unusual because the species was consistently absent during spring. In addition, total lipids and triacylglycerols were low (<15% and <4.5 μg∙animal−1, respectively), suggesting that D. pulex had been pushed into a subsistence niche by the rising salinity levels.

Are the morphometrics of chelicerae correlated with diet in mesostigmatid mites (Acari)?

Gamasid mites are prominent predators of soil communities. Some species are said to be specialized predators feeding on nematodes or arthropods. A conspicuous difference between species is the structure of the chelicerae. We test the hypothesis that measurable attributes of the chelicerae are related to diet. We measured ten morphometric parameters of the chelicerae from 52 species within 29 genera. For 28 species and 26 genera we were able to extract food preferences from the literature and own observations. We found some weak indications that arthropod predators have proportionally larger chelicerae compared to similar-sized species feeding on nematodes or other worm-like diets. The latter are characterized by a larger number of teeth along the digitus fixus and digitus mobilis.

Niche Relationships of Dipodomys agilis and D. stephensi: Two Sympatric Kangaroo Rats of Similar Size

-Congeneric heteromyid rodent species of similar size rarely occur in sympatry and use distinct habitats when they do. We characterized habitat use by two such species, Dipodomys stephensi and D. agilis, at two sites in western Riverside Co., California, and compared their selection of seeds and seed patches in the laboratory. At both localities, D. agilis.and D. stephensi were segregated spatially; D. agilis captured in areas with significantly greater cover of shrubs at both sites. In the laboratory, the species were very similar in choice of seed sizes and native seed species. Substrate use also was similar, but D. agilis avoided heavy substrates more than D. stephensi, and discriminant analysis correctly classified all individuals to species. The species differed significantly in response to light and artificial shrubs; D. agilis foraged under shrub canopies and avoided lighted open areas more than D. stephensi. Dipodomys stephensi consumed significantly more commercial seed with high oil and protein content. These differences suggest that the basis for divergent habitat selection in this case could involve a suite of factors related to effects of habitat on predation risk, water balance and, perhaps, foraging efficiency.

Seasonal changes in material and energy balance associated with reproduction in the green lizard, Lacerta viridis, in western France

Abstract Rates of turnover of oxygen, water and sodium were measured in free-ranging and captive Lacerta viridis in western France during their period of reproduction in May, and again in late autumn prior to their entering winter hibernation. Rates of C02 production and turnover of water and sodium in captive lizards showed little significant variation and these animals appeared to be buffered to a large extent from environmental changes, even though they were exposed to external climatic influences. Overall means for rates of CO2 production in free-ranging individuals did not vary statistically between seasons but considerable individual variation was observed during the breeding season in May. The animals could be divided into 'active' and 'inactive' groups on the basis of their rate of CO2 production and other significant differences were apparent between these two groups: 'active' individuals had increased rates of sodium turnover, lower body water contents and lost body mass during the period of observation whereas the 'inactive' individuals gained mass over the same period. These data suggest that not all individuals necessarily participate in the activity associated with breeding in spring in this species and further behavioural studies would seem appropriate in the light of these physiological data. Calculation of the 'Water Effectiveness Index' for this species from the ratio of water to energy turnover suggests that Lacerta viridis is a profligate utiliser of available resources when compared with similar-sized species of lizards inhabiting desert environments.

A PHYLOGENETIC ANALYSIS OF CHARACTER DISPLACEMENT IN CARIBBEAN ANOLIS LIZARDS.

Twenty-seven islands in the Lesser Antilles contain either one or two species of Anolis lizards. On nine of the ten two-species islands, the species differ substantially in size; 16 of the 17 one-species islands harbor an intermediate-sized species. Two processes could produce such a pattern: size adjustment (or character displacement), in which similar-sized species evolve in different directions in sympatry; and size assortment, in which only different-sized species can successfully colonize the same island together. Previous analyses implicitly have assumed that size is evolutionarily plastic and determined solely by recent ecological conditions, and consequently have tested the hypothesis that character displacement has occurred on each of the ten two-species islands. Other studies have focused only on size assortment. By analyzing such patterns in a phylogenetic context, I explicitly consider historical effects and can distinguish between size adjustment and size assortment. Using a minimum evolution algorithm, I assess evidence for size adjustment by partitioning changes in size along branches of the phylogenetic tree. Size evolution appears rare (a minimum of 4-7 instances of substantial size evolution). In the northern (but not the southern) Lesser Antilles, size change was significantly greater when a descendant taxon occurred on a two-species island and its hypothetical ancestor occurred on a one-species island, thus supporting the size adjustment hypothesis, though size adjustment might have occurred only once. The relative rarity of size evolution suggests that size assortment might be responsible for nonrandom patterns. In both the northern and southern Lesser Antilles, a null model of no size assortment is convincingly rejected. Closely related taxa, however, are usually similar in size, and hybridization between species has been reported. Consequently, similar-sized species might not coexist because they interbreed and coalesce into one gene pool. A null model that only allows species from different "clades" to co-occur is rejected for the northern Lesser Antilles, but is ambiguous with regard to the southern Lesser Antilles. Thus, competitive exclusion is probably responsible for the pattern of size assortment in the northern Lesser Antilles; both competitive exclusion and interbreeding of closely related species of similar size might be responsible for the patterns evident in the southern Lesser Antilles.

Coexistence of Three Congeneric Salamanders: The Importance of Habitat and Body Size

In the southern Appalachians three congeneric salamanders–Desmognathus quadramaculatus, D. monticola, and D. ochrophaeus–are broadly sympatric. D. monticola is intermediate to the others species in body size and in degree of terrestrial habit. This study analyzed the roles of competition, predation, and habitat conditions in limiting the abundance of this "ecologically intermediate" species and in directing its evolution. In field observations, D. monticola regularly used both stream—bank and forest—floor habitats; experimental exclusion from either of these habitats resulted in poor survival. Field enclosure experiments also showed that growth, survival, and habitat selection of D. monticola were altered by the presence of congeners. Interference from conspecifics and from congeners of equal size decreased growth and reduced survival of D. monticola. Predation by large D. quadramaculatus sharply reduced survival of juveniles and caused shifts in activity and habitat selection. I suggest that predation has controlled the evolution of body size and habitat selection in D. monticola and that populations of this intermediate species are limited by the availability of streambank cover as a refuge from predation. Competition may also be important among species of similar size when food is limited.

Colonization by Herbivores of Heliconia spp. Plants (Zingiberales: Heliconiaceae)

The leaf-top herbivore guild of Heliconia spp. is a particularly good subject for the examination of host colonization because individuals may be monitored easily for extended periods of time. Studies of the guild on H. imbricata in Costa Rica and on H. latispatha in Ecuador reveal substantial variation in the rates of colonization among plants. The variation is explained best by the insects' response to environmental conditions, in particular, light and moisture. THE STIMULI PROMOTING HOST CHOICE by herbivorous insects are relatively unknown (e.g., Futuyma and Gould 1979; Fox and Morrow 1981; Rausher 1981; Dethier 1982). Recent attempts to correlate patterns of herbivore choice with taxonomic and ecological groupings of plants are indecisive (Futyuma and Gould 1979, Holloway and Hebert 1979, Fox and Morrow 1981). Most baffling is the variation in herbivore accrual among individual plants within a population: why should herbivore individuals be clumped on certain plants? Suggestions advanced for intra-specific herbivore choice include plant secondary chemistry (Cooper-Driver et al. 1977), plant nutrient content (Myers and Post 1981), herbivore aggregation pheromones (Howe et al. 1976), and environmental conditions (Maiorana 1981). Colonization of the tropical rain forest monocots Heliconia imbricata (0. Ktze.) Baker and H. latispatha Benth. by some herbivorous insects provides insight into this problem. THE LEAF-TOP HERBIVORE GUILD The herbivores that feed upon surfaces of leaves of Heliconia spp. live beneath accumulated debris, and feed upon the epidermis of the host plants' large, horizontallyheld leaves. Detritus of leaves and of other plant parts from trees above Heliconia plants retains moisture even when the uncovered portions of leaves dry between rains. Debris forms patches of habitat for the insects. Both larvae and adults of the insects disperse among the patches of debris. The most common herbivores in leaf-top debris on H. imbricata in Costa Rica are larvae and adults of Cheirispa dorsata Baly (Coleoptera: Chrysomelidae), larvae of Cephaloleia consanguinea Baly (Coleoptera: Chrysomelidae), and the larvae of an unidentified lepidoteran (Fig. 1). Searches of debris upon large numbers of other plant species near colonies of the leaftop guild at La Selva have revealed either species different from those of H. imbricata or no arthropods at all. Other Heliconia species of similar size often accommodate one or two of the species of this guild, but C. consanguinea is specific to H. imbricata (Strong 1977a, b; 1982). At La Selva, H. imbricata is by far the most abundant Heliconia species. Likewise, H. latispatha is the most common Heliconia species at Rio Palenque, Ecuador. There, I have found the leaf-top herbivore guild to include the larvae of two unidentified chrysomelid beetles, one very similar in size and appearance to C. consanguinea, and larvae of an unidentified lepidopteran.

Body Size and Coexistnce in Desert Rodents: Chance or Community Structure?

We use a simple test to evaluate the null hypotheses that desert rodent communities are composed of species assembled at random with respect to body size. This hypothesis is unequivocally rejected for species in the granivore guild: species of similar size (body mass ratios <1.5) coexist less frequently in local communities and overlap less in their geographic distributions than expected on the basis of chance, suggesting that their co—occurrence is precluded by interspecific competition. When granivore species and members of other guilds are combined in the same analysis, the patterns apparent in granivores diminish or disappear. These results indicate that ability to detect community structure depends to a large extent on thorough knowledge of the organisms and choice of appropriate statistical tests. We suggest that recent claims that many communities are indistinguishable from random associations of species are premature.

SEASONALITY, DENSITY AND DIVERSITY OF BIRDS OF A PAPYRUS SWAMP IN WESTERN KENYA

SUMMARYThe commoner birds of a western Kenya papyrus swamp are listed. This avifauna is probably as rich as in any papyrus habitat, dominated by warblers (Sylviinae) in which interspecific competition between species of similar size is reduced by preference for swamp‐edge rather than interior habitats, preference for papyrus over standing water, or vertical habitat partitioning. Comparisons with other west Kenyan habitats show that it is a specialized avifauna with low species diversity indices and few species. Density figures for common species are higher than in forest undergrowth or thicket. There is little ecological diversity of habitat in uniform stands of papyrus which form ecological islands, and this high density may be interpreted as a density compensation on a speciespoor ‘island’ compared to a species‐rich ‘mainland’.Rainfall is the most seasonally variable climatic factor in west Kenyan papyrus habitats. In this climatic area of Uganda and western Kenya there is a modal egg‐laying period from March to June coinciding with the long rains, and a postnuptial primary moult period from June to November, which extends into the short rains of October and November. On average, a complete moult of the remiges takes six or seven months. In general the moult of immatures begins and ends about two months later than adult moult, but birds reared during the short rains had primary moult only half complete at the beginning of the following long rains. There is very little evidence of interrupted moult. The 1969 rainfall pattern was exceptional, with the heaviest rainfall in February, and there is evidence of a correspondingly early onset of postnuptial moult in that year. Females moulted significantly earlier than males in 1969 whereas males moulted marginally earlier in other years, suggesting that female moult schedules are more flexible.

RNA sequences associated with proteins L1, L9, and L5, L18, L25, in ribonucleoprotein fragments isolated from the 50-S subunit of Escherichia coli ribosomes.

32P-labelled 50-S subunits from Escherichia coli ribosomes were hydrolysed under conditions known to give rise to two specific ribonucleoprotein fragments, containing proteins L1, L9, and L5, L18 and L25 respectively. RNA corresponding to these ribonucleoproteins was isolated and purified, and the various RNA fragments obtained were subjected to oligonucleotide analysis. The results showed that the RNA associated with proteins L1 and L9 was very similar to the RNA found with protein L1 after controlled digestion of 23-S-RNA - L1 complexes (described elsewhere); this RNA lies within a region 550-1000 nucleotides from the 3' terminus of 23-S RNA. The RNA associated with proteins L5, L18, and L25 consisted predominantly of two species of similar size. One was 5-S RNA, and the other a fragment of 23S RNA, lying within the region 450-1000 nucleotides from the 3' terminus.

Field investigations on the effects of an organophosphorus pesticide, thionazin, on predacious Carabidae (Coleoptera)

The effects of soil-applied thionazin on field populations of Carabidae were assessed in two fields of potatoes in Berkshire, England. Broadcast at 11·2 or 44·8 kg/ha in a light sandy loam soil, thionazin considerably reduced numbers of Carabids for up to eight weeks after application. Lower catches occurred again six months later when treated soils were rotavated after lifting of the potato crop; these were attributed to the exposure of Carabidae to thionazin residues which had leached into deeper layers of the soil. Dosages of 2·24 or 8·96 kg/ha applied in rows sometimes increased numbers of Carabidae trapped, possibly because of sublethal effects increasing locomotor activity. Carabidae affected most by the treatments were the small diurnally active species such as Bembidion lampros (Hbst), B. quadrimaculatum (L.), and Trechus quadristriatus (Schr.) which were also abundant at the time when the treatments were applied. Larger species such as Harpalus rufipes (Deg.), Pterostichus vulgaris (L.), P. madidus (F.) and Calathus fuscipes (Goeze) were also affected but were generally less susceptible partly because they appeared later in the season when the pesticide had partly disappeared. The rapid disappearance of thionazin from the surface 1·3 cm of soil could account for the low susceptibilities of non-burrowing species; Asaphidion flavipes (L.) which rarely burrowed was less susceptible and Harpalus aeneus (F.) which readily burrowed was more susceptible than other species of similar size.

The Body Temperature of Tenebrionid Beetles in the Namib Desert of Southern Africa

ABSTRACT In direct sunshine the abdomen of living Onymacris brincki, which is covered by white elytra, was 3 − 4 °C cooler than its thorax, while in the same conditions the abdomen and thorax of O. rugatipennis, which is an entirely black beetle, had the same temperature. Since similar effects were observed in dead beetles, the warmer thorax was not due to muscular activity. When the white elytra of brincki were covered with carbon black, its abdominal temperature rose to equal that of rugatipennis. Models, made of pieces of black and white elytra, showed similar effects. The smaller species Stenocara eburnea (with white elytra) showed a smaller and less consistent temperature depression when compared with the similar-sized species S. depressa (which is black). Abdomens of O. rugatipennis, O. laeviceps and Physostema cribripes (all large black beetles) were from 3 − 5 °C warmer than O. brincki, but showed no consistent difference among themselves. When O. rugatipennis was oriented head-on to the sun in its natural environment its thorax was about 4 °C cooler than when its long axis was normal to the sun’s rays. Beetles exposed to sunshine were 12 − 15 °C warmer than they were in the shade. When transferred from one to the other, the greater part of temperature equilibration occurred in about 2 min and equilibration was complete in about 4 min. Observation suggested that beetles thermoregulate by moving between sunshine and shade. Measurements showed that a beetle exposed to alternating periods of 10 sec in sunshine and 30 sec in shade reached a steady temperature of about 33 °C, while the reverse conditions (10 sec in the shade and 30 sec in sunshine) led to a temperature of about 38 °C. In continuous alternations thoracic temperatures remained const within about i °C. Laboratory experiments in which the angle of incidence of the sun’s rays was varied through 180° confirmed the field results and showed that white elytra lower the abdominal temperature of living and dead beetles. Upper lethal temperatures for 30 min in saturated air varied from 50 °C for the desert tenebrionid Onymacris plana to 42-5 °C for the mesic species Trigonopus capicola. In general, upper lethal temperatures correlated well with habitat and habit. Making certain assumptions, analysis of the heat balance of beetles during one exposure in sunshine suggests that the difference between the white elytra of brincki and the black ones of rugatipennis as regards the amount of short-wave radiation reflected is 0-227 cm− 2 min−1, and further, that the reflectivities of the two surfaces are 79% and 38% respectively. The selective advantage of white elytra probably has little to do with heat balance ; the vivid contrast between white and black suggests that the pattern may be aposematic.