摘要:

ABSTRACT.1. This first detailed behavioural field study of any species within the order Embiidina (=Embioptera) examines the function of parental care in the webspinnerClothoda urichi(Saussure) (Clothodidae).2. Time budgets of nymphs and females in different stages of reproduction differ significantly due, in part, to maternal behaviours.3. Nymphs, non‐reproductive adult females and females with nymphs are active only at night when they feed and spin silk. In contrast, females with eggs guard their eggs both day and night, rarely feeding during the 6‐week period prior to hatch.4. Females physically repel egg parasites. In addition, females construct a substantial egg mass covering, of substrate materials and silk, which hinders parasi

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00979.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. This paper tests the hypothesis that selection for dispersal ability within a species influences not only the occurrence and extent of wing reduction but also the tendency or ability of the macropterous individuals to fly.2. Flight thresholds of four species of waterstriders (Hemiptera; Gerridae) were assessed using a tethered flight technique. The species tested varied from monomorphic macropterous (Limnoporus dissortisDrake and Harris), through seasonally polymorphic (Gerris comatusDrake and Hottes andG. buenoiKirkaldy), to primarily apterous (G.remigisSay).3. Condition of the indirect, mesothoracic flight muscles, and presence or absence of mature or developing eggs (for females) were determined by dissection of all individuals immediately following flight testing. Only individuals with normal muscles were included in the analysis of flight thresholds.4. Comparisons among species revealed that average flight threshold and extent of flight muscle histolysis were negatively associated with the proportion of macropterous individuals. Wing reduction was also associated with significant seasonal variation in flight threshold, particularly among females.5. These results support our initial hypothesis, and further indicate that, within the Gerridae, dispersal tendency depends not only on the proportion of macropters but also on the dispersal capability of the macropterous individuals.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00980.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. In order to estimate the absolute larval density in each stage of a larval population of the gypsy moth,Lymantria disparL., in a deciduous forest in northern Japan, the head‐capsule collection method was used. An estimate by this method was compared with estimates based on two kinds of frass collection methods.2. Twenty‐one traps made of cloth were put in a study plot. Each trap was of 24.5 cm diameter. Larval head‐capsules falling into the traps were collected and sorted by hand. On the first sampling occasion, the population was also estimated using the frass‐collection method.3. Larval numbers estimated by the head‐capsule collection method were almost identical to estimates by the two frass methods. Larval numbers entering the four larval instar were successfully estimated by the head‐capsule collection method, and an age‐specific life table was established using the result

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00981.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. A laboratory technique for measuring the number of pollen grains consumed by thrips is described.2.Thrips imaginisBagnall andThrips obscuratus(Crawford) (Thripidae) were studied particularly on pollen of the kiwifruitActinidia deliciosa(A. Chevalier) Liang&Ferguson in New Zealand, andEchium plantagineumL. in Australia.3. Mean daily feeding rates (in grains per thrips per day) ranged from 29 to 843, with an individual rate as high as 1626 forT.imaginislarvae II onE. plantagineum.4. The time taken to feed on a single grain was proportional to grain volume, and decreased with temperature.5. Daily feeding rates were significantly different between pollens, and were higher for smaller grains. The total volume of pollen contents consumed and the total time spent ingesting this volume per thrips per day may be constant with respect to pollen species.6. Daily feeding rates were equivalent to 0.2–0.7% of the average total pollen production of a flower per thrips per day.7. Extrapolation of the daily feeding rates suggests that pollen damage by thrips could sometimes be reducing crop yield or plant fitnes

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00982.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. Overwintering survivorship of pupae of the mimosa webworm,Homadaula anisocentraMeyrick (Lepidoptera: Plutellidae), was examined in several urban habitats in central Iowa during the winters of 1981–82, 1982–83 and 1983–84.2. Survivorship and supercooling point temperatures were determined throughout the winters. Corroborative laboratory studies were conducted during the winter of 1982–83.3. Minimum ambient temperatures that equalled or were below the supercooling point of the insect, at any time, were lethal.4. Prolonged cold exposure below 0°C and above the supercooling point resulted in high mortality levels. To quantify this relationship, a concept of minimum‐temperature exposure was developed by tabulating the number of degrees that the daily minimum temperature was below 0°C for a given sampling period.5. Some mimosa webworm pupae were found to overwinter in highly protected sites (2.5–5.0°C warmer than the ambient air temperatures) in the urban environment, resulting in less minimum‐temperature exposure and reducing the probability of reaching the lethal supercooling p

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00983.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. A rainfall simulator is described that was used to investigate the effects of rainfall on the cochineal insectDactylopius opuntiae(Cockerell). This species occurs in discrete colonies that are protected by a copious covering of opaque‘woolly’wax, and is the most important biological control agent of the prickly pear cactus,Opuntia ficus‐indica(L.) Miller, in South Africa.2. We record the composition of cochineal colonies (stage and number of individuals) in relation to colony size to allow accurate predictions of colony composition from size measurements of the intact, wax‐covered colonies before their exposure to rainfall.3. Even short exposures (15 min) to simulated rainfall (delivered at a rate of about 50 mm/h) resulted in wax erosion, and the effect was most marked in small, recently established colonies. Coverings of compacted wax protected the mature colonies from erosion.4. The number of colonies that were washed off the plant was a function of colony size and the duration of exposure to simulated rainfall. Most of the small, recently established colonies were washed from the plants after 120 min. All of the large, mature colonies, albeit badly mutilated and containing far fewer individuals, remained on the plants even after 240 min exposure.5. Survival of individuals, in colonies of all sizes, was less than about 40% after short bouts of rainfall (30 min). First‐ and second‐instar individuals accounted for most of the observed mortalities, and mortality of all stages increased with increasing rainfall duration.6. These observations provide a partial explanation for the poor performance ofD. opuntiaeas a biological control agent of cacti in higher‐r

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00984.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. The distribution ofDactylopius opuntiae(Cockerell) colonies onOpuntia ficus‐indica(L.) Miller cladodes collected during a prolonged drought, was recorded for the proximal and distal portions of the cladodes, for the exposed and sheltered surfaces, the edges, and in relation to the proximity of the colonies to areoles at the base of the thorns.2. Most of the colonies were found on the more sheltered parts of the cladodes and a disproportionately large number of the colonies on exposed surfaces had settled below the areoles.3. Individuals in colonies on the exposed surfaces were all protected by a relatively hard, compacted wax cover and were thus less vulnerable to simulated rainfall than those on sheltered surfaces. Thorns provided some protection from simulated rainfall for individuals in colonies on exposed surfaces, but not for individuals on sheltered surfaces.4. Natural rainfall greatly reduced the numbers of colonies, but did not significantly change the distribution of the colonies on the cactus cladodes.5. Rainfall does not explain the observed distribution ofD. opuntiaecolonies on the cladodes, but does explain the poor performance of cochineal insects as biological control agents of prickly pear cacti in high rainfall area

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00985.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. 23275 arthropods collected by insecticide fogging from ten Bornean lowland rain forest trees were sorted to approximately 3000 species and assigned to guilds using two sets of criteria.2. The rank order for proportions of guilds of species but not individuals is similar in tropical and temperate canopy samples.3. Misplacement in the guild assignments of a few species can cause important differences in the proportions of certain guilds. This can seriously affect the results of comparisons of different samples, and views on proportional constancy of guilds of species on different trees.4. Guilds of arthropod species such as chewers, suckers, all phytophages, predators, ants and tourists, occur in constant proportions in samples from different tropical trees and this constancy of proportion is similar in samples from groups of‘closely related’and‘distantly related’trees.5. The guild concept of community structure and problems in assigning species to guilds are considered with respect to arthropod samples. The conclusions on constancy of proportion for guilds of species are tempered by remarks on the problems of guild comp

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00986.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. The continuous spectrum of palatability can be divided without difficulty into two halves: the distasteful forms in one half tend to become models and muellerian mimics, the palatable forms in the other half to become batesian mimics.2. Most of the traditionally recognized differences between batesian and muellerian mimicry are valid and useful: negative versus positive frequency‐dependence, detriment versus benefit to the model, convergent evolution versus advergent evolution. None the less in both kinds, mimicry usually evolves by means of a major mutation whose effects are later modified. ‘Supergenes’ tend to be discovered more in batesian mimics than in muellerian mimics. This results from a complex interaction between natural selection on the one hand, and the origin of clusters of genes of related function through tandem duplication on the other.3. Adaptation is not simply the creation of the best of all possible worlds: what natural selection can do is limited by what is possible for the

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00987.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACT.1. Patterns of daily and seasonal activity for seven species of tenebrionid beetles, genusEleodes, were investigated in the shortgrass prairie of northeastern Colorado. The relationship between time of activity, body temperatures, and rates of water loss of the beetles was examined in the field and in laboratory experiments.2. Common species were active from April until the end of October; however, asynchronous peaks of abundance occurred.3. Beetles were diurnally active with peaks of daily activity occurring 2–4 h after sunrise and before sunset. Less than a 2 h shift in mean time of activity occurred between seasons.4. Within species, body temperatures measured in the field closely corresponded to temperatures selected in an experimental thermal gradient; hence, species seemed to prefer particular body temperatures and were most active during times when those temperatures could be achieved. Body temperatures measured in the field approximated ambient temperatures measured in the vicinity of the beetle.5. Significant differences among several species were found for times of daily activity and corresponding body temperatures.6. Ability to resist water loss by evaporation was not correlated with daily or seasonal activity pattern

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1987.tb00988.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY