摘要:

Abstract.1To understand the nature of male aggregations inDrosophila mycetophaga, data were collected on male and female distribution and male spacing on bracket fungi used as mating arenas in cool rainforests of south‐eastern Australia.2Both males and females appeared to be aggregated among bracket fungi that were used as mating arenas. Females were associated with large male aggregations. The probability of a fungus being occupied increased with its area. However, a multiple Poisson regression analysis suggested that fungus area did not affect female distribution when male number was controlled.3The presence of female breeding and feeding resources did not determine where aggregations were formed, because there were aggregations on fungi without resources, and fungi with resources were not used more often than those without them.4D.mycetophagamales did not select and defend territories within bracket fungi, and did not determine female access to areas. However, males were more evenly spaced than expected on the basis of a random distribution, suggesting that males kept apart from each other.5The distribution of the different sexes and male spacing pattern supports the interpretation thatD.mycetophagahas a lek mating syste

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00448.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1Like other checkerspots,Euphydryas gillettiibutterflies may contain the defensive chemicals, iridoid glycosides, which are sequestered from their hostplants during larval feeding.2We analysed the iridoid glycoside content ofE.gillettiiadults from two different populations, Warm Lake, Idaho, and Granite Creek, Wyoming, that have different patterns of hostplant use.3Gas chromatographic analysis of thirty butterflies from the Wyoming population showed that they contained a mean of 1.27 (±0.19 SE) % dry weight iridoid glycosides. Notably, 20% of these butterflies contained no detectable iridoid glycosides.4In contrast, nineteen butterflies from the Idaho population contained a mean of 3.89 (±0.38 SE) % dry weight iridoid glycosides, and all butterflies contained iridoid glycosides.5These results illustrate how the chemical defence of herbivorous insects varies according to differential use of potential hostplant

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00449.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1Two natural populations ofIschnura graellsiiwere studied in north‐west Spain by means of mark‐release‐recapture techniques. Recaptured males were a random sample of the original marked population with regard to date of marking. At O Rosal a greater proportion of young males than old males disappeared after marking; at Lourizán recaptured males were larger than unrecaptured ones.2The number of matings observed in both populations showed great daily variation. Most of the variation is accounted for by climatic variables. Most males (56–65%) and many females (41–45%) were never observed to mate.3Male LMS was highly correlated with lifespan in both populations. At O Rosal, male LMS was also positively correlated with body length, and mated males were larger than unmated males. This surprising result for a non‐territorial species was due to the positive correlation between date of marking and size. There was a positive correlation between body size and mobility for males at O Rosal, but mobility was not correlated with male LMS.4As predicted by sexual selection theory, the standardized variance in male LMS was greater than in female LMS. Variation in mature lifespan explained 16% of variance in male LMS at Lourizán and 2

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00450.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1Outbreaks of tussock moths (Orygia verustaBdv.) on bush lupines (Lupinus arboreusSims) may be very intense, although spatially localized, and may last>10 years. To understand better how such outbreaks may persist, we defoliated lupine bushes using variable realistic numbers of tussock moth larvae, and measured the immediate and delayed impacts of defoliation on the growth and seed production of lupine bushes.2Immediate effects of defoliation included the production of new leaves that were significantly smaller in diameter and biomass, and lower in water content, than the new leaves of undamaged bushes. Also, seed output was reduced by up to 80% on heavily damaged bushes.3In the longer term, surviving bushes recovered remarkably well, despite having received the full range of possible (survivable) insect densities. After 1 or 2 years’rapid growth, surviving bushes were not affected in terms of height, basal stem diameter or volume by their previous defoliation. However, there was a significant tendency for juvenile bushes to produce more seeds the more heavily they had been attacked the previous year.4The ability of the host plant to recover, in terms of its biomass, helps to explain the sustained nature of the insect outbrea

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00451.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1Sexually transmitted diseases (STDs) have rarely been reported in insects and other invertebrates. The majority of those reported involve organisms where sexual transmission is augmented by either vertical (i.e. inherited) transmission, or horizontal transmission, independent of host sexual activity.2We here demonstrate the existence of an STD in the coccinellid beetleAdalia bipunctata. This species bears a parasitic mite of the genusCoccipolipus. We show that, like many other podapolipid mites, this mite is transmitted between host individuals at a high rate during copulation. It also appears to be transmitted at a low rate between non‐copulating individuals.3We show that infected femaleA.bipunctataproduced eggs at a reduced rate, and that the eggs produced by infected females have highly decreased viability. However, no effect of infection upon host longevity was observed.4The results are discussed in relation to the incidences of sexually transmitted disease in invertebrates in general, the causes of disease symptoms, and the importance of this disease in the evolution ofA.bipunctat

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00452.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary.1The geographical distributions of three species of jumping plant lice (psyllids) along an altitudinal transect (988–1300 m a.s.l.) in southern Norway were restricted within the range of their host plantSalix lapponum. One species,Cacopsylla propinqua, occurred at all sampling locations between 988 and 1222 m, whereasC.palmeniwas confined to higher altitudes (1153–1222 m) andC.brunneipenniswas more abundant at lower altitudes (988–1101 m).2C.brunneipennisandC.palmenideveloped only on female catkins. Development times of catkins and psyllids were similar (approximately 50 days) and successful psyllid development depended on close phenological synchrony with catkins.3Thermal requirements for development of female catkins were greater at low altitude (988 m) compared with higher altitude (1222 m), showing local adaptation ofS.lapponumto altitude. In general, thermal requirements of psyllids were less than those of catkins at the same location.C.brunneipennishad higher thermal requirements thanC.palmeni.4Field experiments, using polythene enclosures to elevate temperatures at two sites at different altitudes (by 0.6–1.4 deg. C), showed that insects had an enhanced relative rate of development under elevated temperatures compared with their host plants.5Indices of phenological synchrony were calculated from thermal requirements of psyllids and catkins. Under elevated temperatures, phenological synchrony decreased at both sites. This resulted in the subsequent development of smaller adult insects at low altitude, although at higher altitude, insects developing under elevated temperatures were larger and had a higher survival rate compared with controls.6Effects of temperature on phenological synchrony may explain the limits to the geographical range of psyllids. The consequences of climate change on psyllid populations will depend on the effects of decreased phenological synchrony on insect development and this may differ within the insect's geographica

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00453.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1The ability to use flexible decision rules can be an advantage to parasitoid females searching for patchily‐distributed hosts. In a series of laboratory experiments the hypothesis thatOpius dimidiatus, a solitary parasitoid of the chrysanthemum leafminer (Liriomyza trifolii), adjusts the time she allocates to searching for her larval hosts in response to both patch qualities and experiences with hosts was tested by varying such patch parameters as area, presence of host mines and density of host mines, and by allowing ovipositions and encounters with parasitized hosts.2Though leaf area was not a factor, the presence of host mines in a leaf did increase the time a femaleO.dimidiatusspent searching, over time spent on unmined leaves.3When host mine density was increased, females responded by increasing their search period in a density‐dependent manner, suggesting a perception of patch quality.4Ovipositions in hosts caused females to reset their‘giving‐up time’(GUT), or increase search intensity, by adding an amount of search time that increased with each successive oviposition. Conversely, encounters with parasitized (unsuitable) hosts incremented the GUT, but by an amount that decreased with each successive

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00454.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1To determine if trees in urban or ornamental plantings are more susceptible to attack and receive more damage to foliage by herbivores than trees in natural forests, we compared the amount of leaf damage caused by several guilds of insects feeding on seven species of native, broadleaf trees in two geographic locations.2Total leaf damage did not differ significantly between urban or ornamental and natural forests, although trees in natural forests tended to have slightly higher levels of leaf damage.3Damage caused by chewing insects was consistently higher on trees in natural forests than in urban or ornamental plantings. All other feeding guilds showed no consistent pattern in levels of damage between the two habitats.4Total damage levels were highest on canopy trees and lowest on understorey trees.5These results are inconsistent with the view that trees in urban or ornamental settings are more susceptible to insect attack than trees in natural forests.6The lower level of foliar damage caused by chewing insects on trees in urban or ornamental plantings may arise because of low rates of dispersal by insects into urban environments, higher levels of plant resistance to insect attack in urban or ornamental plantings, or lower survival rates of herbivorous insects in urban environments.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00455.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1The effects of intraspecific and interspecific larval competition on larval survival, adult size, adult longevity and fecundity were quantified in four species of coexistingLuciliablowflies:illustris, silvarum, sericataandcaesar.2There was a general negative effect of increasing density on larval and adult survival, size and fecundity. Additionally, complex species‐specific and frequency‐dependent responses were identified, which were not expected in these biologically and morphologically closely similar species.3Lucilia illustris, the numerically dominant species in the natural community, was a superior competitor toL.silvarumat intermediate densities but an inferior competitor at high density. Such nonlinear responses may be related to differences in the life histories and larval behaviour of the species (bigger eggs and more contest‐type outcome of competition inL.silvarum).4We parameterized a model of interspecific competition on a subdivided resource in an attempt to reconcile the conflicting results on larval competitive abilities and the abundances of the species in the field. Using laboratory and field‐estimated parameter values the model predicted coexistence ofL.illustrisandL.silvarumand the observed numerical dominance of the former species. The average densities of flies in the field are limited to relatively low levels, apparently preventingL.silvarum(the superior competitor at high density) from dominating and excludingL. il

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00456.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.1In a 16‐month study in Bangalore, India, about 35% of the newly founded colonies ofRopalidia marginatawere single foundress colonies and the remainder were multiple foundress colonies with two to twenty‐two individuals.2Larger colonies did not have a significantly higher per capita productivity, did not produce significantly heavier progeny and did not produce them significantly faster than smaller colonies did.3Predation by the hornetVespa tropicaappeared to be independent of group size.4Single foundress colonies failed more often but not often enough to make them have a lower average per capita productivity, compared to multiple foundress colonies.5Some of the advantages of multiple foundress associations came from the greater predictability of their attaining the mean per capita productivity, the relatively lower rates of usurpation experienced by them compared to single foundress colonies, and the opportunities provided by queen turnovers for workers to become replacement queens and gain direct individual fitn

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1995.tb00457.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY