摘要:

Abstract.1. At Halcyon Hotsprings, British Columbia, Canada, male and femaleArgia vividaHagen encountered to mate in two different ways.2. In the morning (before 12.30 hours solar time), males basked at sunspots in the forest and darted out at passing females, attempting to take them in tandem (the first method of encounter).3. If a male was successful, the pair engaged in a 31.3±4.8 min copulation followed by an hour of tandem flight before beginning oviposition.4. As the day progressed, unmated males moved slowly toward the water and arrived at the water at about the same time as the earliest ovipositing pairs (1131±27.5 min solar time).5. Males retained their grasp on their mates during oviposition (contact‐guarding) but since some tandems separated during oviposition, non‐tandem males at the water could capture recently released, gravid females (the second method of encounter).6. The new pairs performed a brief copulation (10.2±3.38 min) and began ovipositing immediately thereafter.7. Some females that avoided recapture attempted to oviposit unguarded.8. We believe the long duration of morning copulations and period of tandem constitute a male strategy, which we call ‘pre‐oviposition guarding’, to guard females until it is warm enough at the oviposition site for the females to begin ovipositing.9. Separation of tandems during oviposition may be initiated by either member of the pair and we suggest that one benefit to a female of leaving a guarding mate is increased efficiency of oviposition when the intensity of male harassment is low.10. The mating system ofA. vividathus comprises a series of complementary male and female matin

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00819.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. Regional scarabaeid dung beetle assemblages in southern Africa may contain over 100 species, ranging in live weight from 10 mg to 10 g. These show a wide variety of dung‐use and reproductive strategies.2. To facilitate analysis of these diverse assemblages, a system of classification analogous to guilds is proposed. Scarabaeid dung beetle species are allocated to one of seven functional groups (FGs) according to the way they use and disrupt dung. Each group therefore contains a set of species which are functional analogues of each other. This classification provides a conceptual framework within which to analyse the structure of dung beetle assemblages and the interactions between dung beetles and other dung‐breeding species such as coprophagous flies.3. There is a clear hierarchy of functional groups in their ability to compete for dung. Competitively dominant groups such as the large ball rollers (FG I) and fast‐burying tunnellers (FG III) are mostly large, aggressive beetles which rapidly remove dung from the pad. The smaller ball rollers (FG II) are also effective competitors for dung. Subordinate groups are those which bury dung slowly over many days (FG IV and V) and those which breed inside the pad (FG VII, endocoprids). Kleptocoprids (FG VI) breed in dung buried by other beetles and so are not part of the hierarchy.4. The use of this classification is illustrated by reference to three contrasting assemblages of dung beetles in a summer rainfall region of southern Africa. The potential of these beetles for biological control of dung‐breeding flies is di

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00820.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. The hypothesis was tested that intraspecific behavioural interference does not adversely affect the feeding behaviour of adults of three predatory coccinellid species,Chilocorus nigritus(F.),C.bipustulatus(L.) andC.infernalisMulsant, at densities found under field conditions.2. Feeding rates on mature oleander scaleAspidiotus neriiBouché were evaluated by two methods at various predator densities. Proportion of the population dispersing was also measured for one of the species.3. Feeding rate did not decrease and dispersal did not increase with increasing predator density. No significant behavioural interference that might have reduced predatory efficiency was observed, counter to assumptions on which published interference models are based.4. Results here help to explain the relative importance of parasitoids and predators in the effective control of red scaleAonidiella aurantii(Mask.). The results also provide guidelines for release of these bio‐control agen

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00821.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. Sex ratio in the ectoparasitoid,Diglyphus begini(Ashmead), attacking larvae of the dipterous leafminerLiriomyza trifolii(Burgess) in glasshouse marigolds, is best depicted by a model where sex ratio varies as a function of host size.2. MaleD. beginiprogeny are produced in hosts significantly smaller in size than those producing female progeny.3. Female wasps attack and oviposit on the largest leafminer larvae available and whether a host is large or small depends upon the size of the other hosts attacked.4.Diglyphus beginifemales adjust the thre:shold size for the change‐over in sex allocation relative to the size of hosts attacked; however, the sex ratio is maintained at between 60% and 70% males.5. The patterns observed in these glasshouse studies are not due to sex‐specific differential mortality or superparasit

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00822.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. The population dynamics ofTortix viridanaL. (Lepidoptera: Tortricidae) andOperophtera brumataL. (Lepidoptera: Geometridae) on the pedunculate oakQuercus roburL. are driven by the degree to which larval hatch coincides with oak budburst in spring.2. Experiments with first instar larvae demonstrate thatT. viridanahas a much narrower dietary breadth, is less inclined to disperse from closed oak buds, and can resist starvation for longer periods than the polyphagousO.brumata.3. As a result of its specialist foraging strategy,T. viridanamay be less susceptible to mortality associated with colonization of oak in spring thanO.brumata.This may explain whyT. viridanapopulations are, on average, higher.4. These results are discussed in the light of previous work which described the competitive advantage ofO. brumatain field cage experiments. Stochastic mortality factors, which drive population change in both species independently of competition, favourT.viridanalarvae, and over‐ride the competitive superiority ofO.brumat

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00823.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. Individuals of long‐winged waterstrider (Gerridae) species were found in spring far from their breeding habitats, which indicates that they fly before reproduction.2. Field samples and laboratory studies show that once they return to their breeding sites, many individuals of three waterstrider species (Gerris odontogaster(Zett.),Gerris lacustris(L.) andLimnoporus rufoscutellatus(Lat.)) histolyse wing muscles and lose flight ability during their reproductive period.3. The extent of flight‐muscle histolysis varies with environmental factors. Food scarcity affects flight‐muscle histolysis inG.odontogasterfemales. InG.Lacustris, flight‐muscle histolysis was more common in the laboratory than in the field samples. Proportionately more females than males lost their flight ability by the end of the reproductive period.4. Flight ability had direct costs in reproductive potential with (non‐flyer) females, which histolysed their flight muscles, laying more eggs than (flyer) females, which maintained flight ability. This was also the case during food scarcity. Non‐flyer males ofG.odontogastersurvived longer than flyer males.5. Spring migration was distinguished from dispersal during the reproductive period, because these flights serve different functions. Flight‐muscle histolysis of females during reproduction is a qualitative reproductive option, with a trade‐off between dispersal ability and reproductive potential. Ability to change reproductive behaviour depending on environmental conditions increases an individual's ability to cope with a large vari

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00824.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. We examined the preference of larvae of the Mexican bean beetle,Epilachna varivestisMulsant (Coleoptera: Coccinellidae), for foliage of soybean (Glycine max[L.] Merr.) grown under several levels of water deficit. Third instar larvae were exposed simultaneously to excised foliage from plants that were either well‐watered (control) or had experienced water deficits (treatment).2. Water‐deficient plants were re‐watered 12 h prior to initiating feeding trials to eliminate physical differences between control and treatment foliage such as leaf water potential, diffusive resistance, relative water content, and foliage toughness.3. Examination of the free amino acid contents of re‐watered and excised foliage indicated that amino acid concentrations increased markedly in foliage grown under water deficits, and that this increase persisted during the preference tests.4. Larvae preferred control foliage, but shifted preference to treatment foliage under mild water deficits. When the leaf water potential of water‐deficient treatment foliage was lower than – 1.13 MPa or when it was more than 0.5 MPa lower than that of control foliage, larvae preferred to feed on foliage from well‐watered control plants.5. The expression of preference for well‐watered control foliage was coincident with increases in the concentrations of total free amino acids and individual free amino acids in the water‐deficient treatment foliage.6. These results are inconsistent with White's (1974) hypothesis because Mexican bean beetle larvae avoid plants grown under water deficits that have increased concentrations of

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00825.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. We examined the effect of water deficits in soybean,Glycine max[L.] Merr., on the growth and survival of Mexican bean beetle larvae,Epilachna varivestisMulsant (Coleoptera: Coccinellidae).2. Larvae were reared under growth chamber, glasshouse, and field conditions on foliage from plants that were either well‐watered or subjected to water deficits.3. Larval survival, growth rate and pupal weight were reduced, and development time was increased when larvae were reared on foliage from plants subjected to water deficits. These results are contrary to White's (1974) hypothesis that water deficits in plants cause increased growth and survival of herbivorous insects.4. Changes in foliage chemistry caused by water deficits, possibly in the concentration of free amino acids, are the most likely causes of the observed effects on growth rate and development time. However, under glasshouse and field conditions, physical changes in foliage and/or the foliage's environment that accompany water deficits are also importan

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00826.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. We determined the phenology of the shrubSpiraea latifoliaAit. Bork. (Rosaceae), which has indeterminate shoot growth, and the effects of phenological changes in leaf quality on growth rate of the early‐spring feeding buckmoth caterpillars,Hemileuca lucinaHy. Edw. (Saturniidae).2. Leaves, regardless of whether they were newly expanded or several weeks old, were tougher later in the growth season (mid‐June) than similarly aged leaves collected earlier; correspondingly, water and nitrogen content for leaves of all ages declined through the larval period. By July, newly expanded leaves had no more nitrogen than mature leaves.3. Relative growth rate of third instar larvae fed new leaves or a mixture of new and mature leaves in early June was higher than that of those fed mature leaves, and efficiency of conversion of digested food to biomass was higher for larvae fed new leaves than for those fed mature leaves or a mixture.4. In another experiment, larvae were reared on new leaves through the fourth instar and then fed a diet of new, mature or a combination of new and mature leaves, a regimen that was similar to the phenologies of both plants and caterpillars in the field. There was no difference in time to pupation or pupal weights among these treatme

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00827.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. A simulation model is presented which describes, from field‐estimated parameters, the effects of daily survival rate and proportion of sunny days on the lifetime egg production of females of the damselflyCoenagrion puella(L).2. Lifetime egg production increases with daily survival rate and proportion of sunny days.3. Estimates of mean lifetime egg production per female in bad and good summers in northern England ranged from 333 to 740.4. The distribution, as well as the proportion, of sunny days influences lifetime egg production. For a given combination of daily survival and proportion of sunny days, lifetime egg production decreases as the distribution of sunny days becomes more clumped.5. Lifetime egg production is largely determined by chance; females who begin their mature adult life during a period of sunny weather can produce many times more eggs than those whose mature adult life coincides with cloudy day

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY