摘要:

Abstract.1Males ofHermetia comstockiWilliston compete for territorial control of certain agaves and yuccas. Winners copulate with females that visit these plants solely to acquire a mate.2Males vary in body weight by more than an order of magnitude and larger flies almost always defeat smaller ones in aerial contests for control of landmark territories.3The mean body size (as measured by wing‐length) was significantly greater for males retaining residency at a site for at least one hour compared to males unable to do so. Likewise, males able to return to a perch site in the study area on more than one day were larger on average than males unable to do so.4Male preferences for landmark territories remained similar across years. Large males dominated the perch landmarks most likely to be occupied by males and most likely to be visited by females.5Despite the fighting and territorial advantages enjoyed by large males, the mean size of males found mating with females was not significantly larger than that of the general population.6The apparent failure of large males to secure a statistically significant mating advantage may be a statistical consequence of the small sample size of males observed mating. On the other hand, any mating advantage of large males may be reduced because (a) receptive females visit many different landmarks, (b) females mate with the first male they encounter at a landmark, regardless of his size, (c) there are usually many vacant landmarks available for smaller males, and (d) even popular territories are often open to small males, thanks to the low site‐tenacity of territory own

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01073.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Two contrasting hypotheses concerning patterns in food web structure within pitchers ofNepenthesare tested using new information from six species ofNepenthesfrom Borneo.2In general, predictions that webs will be more complex, and the food chains they contain will be longer, the closer they are to the centre ofNepenthesspecies diversity, are supported.3ForNepenthes albomarginata, a widespread species with a distinctive north Bornean form, a contrasting pattern is evident explicable in terms of the morphology of the pitchers and local habitat preferences.4General explanations for food web patterns will always be susceptible to exception, reflecting nuances of natural history.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01074.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Thermal constraints on flight acivity limit the pollinating effectiveness of bees. Each species of social bee has a microclimatic ‘window’ within which foraging flight can be sustained.2To predict whether a given species of social bee is worth testing as a pollinator in a given climate, it is useful to know at least the lower limits of that microclimatic ‘window’. We consider how information from a series of bee counts through a day can be used to characterize a bee species in terms of activity/microclimate relations as a basis for predicting the diel pattern of foraging activity of a bee introduced into a new climate as a pollinator.3We discuss the relative merits of bee counts at a foraging patch and counts based on hive traffic as indices of the proportion of bees active.4We suggest that the activity/microclimate relations of a species be expressed in terms of the lower threshold black globe temperature for flight activity. Black globe temperature,Tg, is easily measured with inexpensive equipment, and can substitute for measurements of ambient temperature and radiation as a predictor of diel patterns of bee activity.5We use examples of field data to explore the relationship between microclimate and activity for the honeybeeApis melliferaand several species of bumblebee,Bombus.Regression analysis is used to relate activity toTgand to identify the lower temperature threshold for activity from field bee counts.6In field studies analysed here, the bumblebeesBombus terrestrisllucorum, B.pascuorumandB.hortorumbegan foraging at lower temperatures than honey‐bees orB.l

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01075.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1The amino acid content of phloem exudates from leaves and of aphid honeydew were adopted as indices of the nutritional quality of phloem sap for aphids. Four plant species and associated leaf‐dwelling aphids were investigated: the sycamoreAcer pseudoplanatusand sycamore aphidDrepanosiphum platanoides; Prunus domestica(victoria plum) and the mealy plum aphidHyalopterus pruni; and the spindle treeEuonymus europaeusand broad‐beanVicia faba, both hosts of the black bean aphidAphis fabae.2The concentration of amino acids in the phloem exudates varied with: (a) plant species (greater in the herbViciathan in the tree species), (b) season (greater in the autumn than summer forAcerandEuonymus), and (c) position (greater in flush leaves than mature leaves ofPrunus).3ForAcerandPrunusand their aphids, the concentration of amino acids in phloem exudates was significantly correlated with the amino acid content of the aphid honeydew.4The amino acids in all exudates and honeydew were dominated by non‐essential amino acids (glutamic acid, glutamine, asparagine or serine, varying with season and between plant species). The sole major discrepancy between the amino acid profiles of exudates and honeydew was the production of asparagine‐rich honeydew by aphids feeding on leaves, whose exudates were dominated by glutamic acid; this applied to bothH.prunion maturePrunusleaves andDrepanosiphum platanoideson summer‐leaves ofAcer.5It is suggested that EDTA‐exudation may be a useful technique to study nutritional correlates of aphid life cycles, e.g. the time of migration between primary and secondary

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01076.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Adults of the noctuid mothAutographa gammaundertake seasonal migrations into areas where they are unable to breed continuously. Individuals migrate into Britain each spring, and offspring of these migrants probably return in autumn to over‐wintering areas in North Africa and the Middle East. However, the existence of these return migrations has been questioned.2Insects usually migrate during the adults' pre‐reproductive period (PRP). The length of this period is therefore an index of migratory potential since individuals with longer PRPs have more time to express their potential for flight and to travel further before becoming sexually mature.3Offspring of insects from Morocco, Britain and Germany showed that, under both long and short photoperiods, PRP increased with latitude over the range 34–53°N. There were significant genotype—environment interactions in the effect of photoperiod on length of PRP.4However, PRPs of offspring from insects collected in Sweden were no different under a long photoperiod from those of offspring collected further south, and were significantly shorter under a short photoperiod than those of insects from Morocco.5With the exception of Swedish moths, offspring from insects collected at higher latitudes had longer PRPs and, therefore, the potential to travel further during migrations. The ability of some individuals to respond to environmental cues signalling habitat deterioration will further increase their potential to return to over‐wintering areas fur

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01077.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1The yellow subterranean antLasius flavusis generally considered to have a single queen in mature nests. Yet, many anecdotal observations have suggested that the conspicuous earth mounds of this ant may, at least occasionally, contain several queens and their offspring.2To estimate the number of matrilines per mound, samples for horizontal starch gel electrophoresis were collected from a total of thirty‐seven mounds in three sites of old chalk‐grassland in southern England.3Allozymatic variation at an esterase and hexokinase locus showed that probably more than 50% of the mounds contained more than one queen and that the mean number of queens per mound is at least 1.5–2.4Further results strongly suggested that workers from different matrilines may share the same galleries, at least in the top of the mound.5The apparently variable social structure ofLasius flavuscolonies is discussed, both technically and with reference to ecological processes related to the presence of ants in the nest m

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01078.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1A wild bruchid seed‐predator,Kytorhinus sharpianus, has a complex life cycle consisting of bi‐ and trivoltinism on a wild leguminous plant,Sophola flavescens.Observations of adults showed significant female‐biased sex ratios (from 1:2 to 1:6) for nine generations over 4 years.2To investigate the potential effects of larval competition on the sex ratio, we altered the number of hatched eggs per seed and counted emergent males and females under laboratory conditions. Although only one adult could emerge per seed, the ratio of the females that emerged increased with the number of hatched eggs per seed. However, the sex ratio was not significantly different from 1:1 in the case of one hatched egg per seed.3We dissected seeds bearing two hatched eggs at regular intervals, and classified the surviving and the dead larvae according to their developmental stage. Over time, one larva within each seed always survived, while the other larva died from the second to fourth instar before the seed resource became exhausted.4In order to study the effects of the difference in the stages of two larvae in a seed on the emergence sex ratio, we manipulated intervals between the first and second ovipositions in the laboratory. As the difference in developmental stages of the two larvae increased, the closer to 1:1 the emergence sex ratio became.5Field observations, however, showed that about 60% of infested seeds were bored by only oneK.sharpianuslarva. This suggests that female dominance in larval competition within a seed may be relatively unimportant in causing the female‐biased sex ratio in th

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01079.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1To determine whether an aphid is ‘aware’ of which plant it is on, clones of a host alternating aphid,Cavariella aegopodiiScop., reared on its primary (Salix) or secondary (Daucus) host, were subjected to autumnal conditions.2Old clones produced males and egg laying females when exposed to autumnal conditions on the primary host but autumnal migrants and males when on the secondary host.3Unlike some other host alternating aphids,Cavarielladid not have to spend a period on the secondary host or go through the spring migrant stage before producing sexuals.4The adaptive significance of a host alternating aphid being ‘aware’ of which host plant it is on is discussed in the light of these

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01080.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1From 10 years' records of moths caught in a light trap at Eilat, Israel, eleven selected occasions with sudden increases in catch involving seventeen species were related to accompanying changes in wind.2At all times of the year examined, sudden increases in catch of all species were associated with winds changing direction to blow from the Nile Delta or from the Levant.3All seventeen species are inferred to be windborne over at least several hundred kilometres.4The results are consistent with huge plumes of moths streaming downwind each night from the Delta and the Levant, sometimes crossing Eilat, sometimes crossing the Mediterranean, but more often passing into the deserts.5Plumes are produced throughout the breeding season of each species.6The results are probably representative of migration elsewhere from the southern limits of breeding on rain‐fed vegetation, with inferred widespread adult mortality and renewed breeding most likely after migration on brief spells of southerly wind

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01081.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Caterpillars of the myrmecophilous butterflyMaculinea rebelishowed strong evidence of contest competition when introduced at high densities to laboratory nests ofMyrmicaants.2This is attributed to the direct feeding of caterpillars by workers, which select a few individuals to nurture when food or ant numbers are limiting. It contrasts with published data for a congener,Maculinea arion, which has predacious larvae and experiences scramble competition in crowded ant nests.3Worker ants from twoMyrmica rubracolonies (I and II) were used to found the laboratory nests hostingMaculinea rebeli.Nests from each source reared a similar biomass ofMaculinea, but whereas those containingM. rubraI workers reared eight to ten lightweight caterpillars each, cultures from colony II reared half as many caterpillars, each of about double the weight.4Differences in nest capacity may be due to the different social structures of colonies I and II at the start of the experiment.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01082.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY