摘要:

We studied predation of gypsy moth,Lymantria dispar(L.), egg masses in two study areas. In Connecticut, individual egg masses were mapped and examined from February to April. Predation rate, expressed as the mean amount removed from an individual egg mass, increased gradually from 30% in February to 53% in April. The percentage of all egg masses upon which some predation was observed increased from 67% to 89% over the same period. Sixteen of 105 egg masses were completely destroyed. Three species of birds were observed feeding on egg masses in the field. I an aviary study, four out of five bird species fed on egg masses with and without alternative foods. Three species of captive small mammals never ate egg masses. In West Virginia, an exclosure experiment revealed that vertebrate predators accounted for 9.3% of egg mass predation from August to April, whereas invertebrates accounted for only 1.5%. Only 5 of 146 egg masses were completely destroyed. Although it is theoretically possible that mammals were responsible for some predation, the gradual nature of egg removal, direct observations of avian predation, and the fact that no mammal has ever been observed to eat an egg mass in field or laboratory leads us to believe that birds were responsible for the observed predation. We conclude that egg mass predation is a variable but potentially important gypsy moth mortality facto worthy of further study.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.571

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The aim of this study was to measure the effects of an increase in the density of the Colorado potato beetle,Leptinotarsa decemlineata(Say), on this insect. Two groups of 20 potato plants,Solanum tuberosumL., ‘Superior’, were subjected to defoliation by the Colorado potato beetle. The first group was infested by 15 larvae per plant and the second by 40 larvae per plant. Measurements of adult body weights were taken, as well as of the quantity of lipid reserves of adults collected upon emergence. Insects originating from plants infested by 15 larvae were significantly heavier and had accumulated significantly more lipid reserves than adults originating from plants infested by 40 larvae. The percentage of lipids over body weight was significantly lower at a density of 15 larvae per plan than at a density of 40 larvae per plant. The effects measured in the 40 larvae per plant group are the result of intraspecific competition phenomena.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.576

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Life-history characteristics of four populations ofCoccinella septempunctataL. were quantified and compared at 26°C and 18:6 (L:D) h on a diet of pea aphids,Acyrthosiphon pisum(Harris). Populations were from two locations in the United States (Iowa and Delaware)and two locations in Eurasia (France and Ukraine/Moldavia/Crimea). Large intrapopulation variation was observed in preoviposition, interoviposition, and number of days on which eggs were laid. This variation was a result of 10–35% of females entering diapause, whereas most females initiated oviposition within 12 d of eclosion an continued egg laying with interoviposition periods of<6 d. No significant differences among the four populations were detected in preoviposition, interoviposition, or number of days on which eggs were laid. In addition, preimaginal development time, sex ratio, and life table parameters, including intrinsic rates of increase and fecundity, did not differ significantly among the four populations. On the basis of the parameters measured, we conclude that these four populations of C.septempunctatahave not undergone local adaptation that would define these populations on the basis of geographical origin.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.581

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Phytophagous insects representing 37 families and 88 species fed on tarbush,Flourensiacernua DC. Thirty-nine of these species were polyphagous, 11 were oligophagous, and 2,Goniatron planum BrunerandBuccalatrix flourensiaeBraun, were specific or apparently restricted to tarbush. The feeding specificity of 36 species was not determined. None of the phytophages substantially damaged tarbush. The psyllidKuwayana medicagnisCrawford was one of the most common insects on the plant. It caused moderate leaf curling in ≍7% of the foliage in early spring. Relative frequency, associated plant parts, geographic distribution, and phenology of insects on tarbush are also reported.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.588

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Hoverflies are potentially important in many agricultural and horticultural crops as biological control agents. The two most abundant species of hoverflies present in the New Zealand agricultural landscape areMelanostoma fasciatum(Macquart) andMelangyna novaezelandiae(Macquart), both of which ar aphidophagous and also prey on young lepidopteran larvae. Information regarding the phenology and ecology of these species is quite limited but is needed if the contribution of these predators to biocontrol is to be enhanced. The main work reported here concerns the trapping of large numbers of hoverflies to investigate their phenology; these flies were subsequently assessed for the pollen type take and for wingwear. Foraging behavior, optimal trap color, and ideal trap-emptying rate were also studied. There was good evidence of a second generation of hoverflies occurring in late summer and pollen preferences for both species of hoverfly were exhibited. The foraging behavior of the two species differed in relation to the number of flights made and the overall distance traveled over fixed time intervals. Yellow was the most efficient color for trappingM. novaezlandiaebut forM. fasciatumyellow, white, and blue did not differ and green was poor. The value of the work in providing backgroun ecological information for possible enhancement programs for hoverfly populations on farmland is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.595

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Female and maleAmblyseius longispinosus(Evans) andA. womersleyi(Schicha) were reared in an incubator at 28°C and a photoperiod of 13:11 (L:D) h. They were supplied with eggs ofTetranychus kanzawaiKishida for food.A. longispinosusmatured in 5.02 and 5.0 d, and consumed 13.84 and 11.2 spider mites eggs, respectively.A. womersleyimatured in 4.92 and 4.67 d, and consumed 15.32 and 11.54 spider mite eggs, respectively. In the first 10 d after ec1osion, adult femaleA. longispinosusandA. womersleyiconsumed an average of 26.43 and 32.07 spider mite eggs daily, and laid 2.92 and 3.07 eggs per day, respectively.A. womersleyideveloped slightly faster thanA. longispinosusand was more voracious. Larvae of both species were observed eating spider mite eggs. Adult femaleA. womersleyiincompletely consumed spider mite eggs when food was abundant. When mated with maleA. longispinosus, all femaleA. womersleyioviposited but with reduced fecundity. Only male offspring were produced and 47.8% of eggs were nonviable. However, only 1.5% of femaleA. longispinosusthat mated with maleA. womersleyioviposited, but offspring of both sexes were produced. Hybrid F1progeny inherited the maternal setal length of dorsal seta L8 in all reciprocal matings. These findings suggested that these two mites are distinct species. Their life cycles, food consumption, reproductive compatibility, and geographical distribution are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.601

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Field recruitment on 10 solanaceous plant species by adult Colorado potato beetles,Leptinotarsa decemlineata(Say), and their oviposition, was investigated by frequent collection of adults and eggs from replicated Latin-square plots over 5 yr in Michigan, Maine, and Massachusetts. Preferred plants for adults were potato, Solanum tuberosum L.; bitter nightshade,Solanum dulcamaraL., and buffalobur,Solanum rostratumDunal; eggplant and horsenettle,Solanum melongenaL. andSolanum carolinenseL., were of intermediate rank in recruitment of adults. The remaining species (tomato,Lycopersicon esculentumL.; black nightshade,Solanum nigrumL.; silverleaf nightshade,Solanum eleaegnifoliumCavanilles; groundcherry,Physalis heterophyllaNees; jimsonweed,Datura stramoniumL.) were not preferred. Adult recruitment and oviposition changed over the season and differed from site to site, but was not influenced by the host-plant origin of recruited adults. Daily collections of adults in Massachusetts in 1991 showed four distinct periods of adult recruitment. These differed in relative importance depending on whether plots were near or distant to previous and current year's potato fields. Early overwintered recruitment was highest and relatively less different between near and distant plots, reflecting the importance of flight during this period. Late overwintered recruitment was mostly by short-distance dispersal of adults that had already fed on potato plants, based on oviposition of collected females. Summer females also appeared to be previously fed, and their recruitment to distant plots suggested dispersal mostly by flight. Prediapause dispersal resulted in recruitment mostly to plots a short distance from potato fields. Reproduction, as measured by egg masses per adult, increased over the season, with summer adults showing the highest egg mass-adult ratio. Recruitment of adults and their oviposition in the field were positively associated with no-choice assays of fecundity and larval survival in the laboratory using the same plant species, but with relatively more rejection of intermediate-ranked hosts in the field.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.608

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Effects of temperature on the larval and pupal developmental times, adult emergence times, and survival of the pea weevil,Bruchus pisorum(L.),were examined at a range of constant temperatures. This study provided an alternative approach to analyzing stagefrequency data for determining stage transition times. It differed from the nearest published method in two vital areas: stage frequencies were expressed as the inverse of the proportion of insects in the sample that had not reached the relevant stage; mean-stage transition times were estimated by fitting a nonlinear curve to the changes i proportions with time. Mean developmental times for instar II, III, and IV, and mean adult emergence times were obtained by subtracting the estimated mean stage transition time from the mean of the previous stage. Temperature-mean developmental time relationships were described with nonlinear functions, which provided curves with a good fit, with r2ranging from 0.964 to 0.998. Mean developmental times were 3- to 5-fold longer for instars III and IV than for instars I and II.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.623

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Gravid females ofRhopalomyia solidaginisLw. oviposit on the vegetative shoot buds ofSolidago altissimaL., and their emerging larvae induce the development of conspicuous, rosette galls with varying numbers of larval chambers per gall. Most galls have only one larval chamber, whereas some have 2-12 chambers. These differences in the number of larval chambers per gall result in variability in the dimensions of galls. Gall populations from several old fields of central Pennsylvania were harvested to assess the morphometric relationships within galls of various numbers of larval chambers, energy allocation pattern among gall components, and host-plant energy allocation to the galls. We found that the normal stem diameter, a measure of host-plant vigor, is a predictor of gallmaker performance. Also, gall sizes likely vary because the gall midges differ in their ability to induce galls but primarily because of variation in the number of larvae per gall and in the quality of different host genotypes. We also found that the strong relationship between the number of larval chambers and the gall stem diameter indicated the stimulation of the goldenrod genotype to create a strong resource base for accommodating the gall. However, our results suggest the possibility of competition among siblings (when the gall houses multiple larvae) for host-plant resources. Our energy estimates reinforce the role of host-plant quality in determining the gall quality.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.635

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The effect of concentrations of carbon dioxide (C02) that can be produced by biological respiration (7.5–19.2%) on oviposition of adultTribolium castaneum(Herbst),Cryptolestes pusillus(Schönherr), orC. ferrugineus(Stephens) was determined. Relative to controls,T. castaneum,C. pusillus, andC. ferrugineus, exposed to 7.5% CO2for 1 wk, had numbers of offspring reduced by 43, 94, and 50%, respectively, and the total population at 6 wk was reduced 53, 84, and 19%, respectively. With levels of ≥17.1%CO2for 1 wk, no offspring were produced and exposed adults had high mortality. Eggs and subsequent immatures ofTribolium confusumJ. du Val,T. castaneum, orC. ferrugineuswere exposed for 3 wk to elevated levels of CO2at 22°C. Insect development was similar at 7.5 and 8.6% CO2with mean mortality 43, 62, and 30% greater than controls forT. confusum,T. castaneum, andC. ferrugineus, respectively. Also, mean levels of 5.8–8.3% CO2for 7 wk reduced, on all sampling dates, populations ofT. confusumby 85%,T. castaneumby 99%,C. pusillusby 68%, andC. ferrugineusby 54%. AlthoughT. castaneumhad a greater oviposition rate than C. pusillus at 7.5% CO2, immature mortality was greater forT. castaneum. Based on long-term exposure to levels of CO2which can be produced by biological activity that affects oviposition and immature development, species in increasing order of sensitivity to CO2areC. ferrugineus,C. pusillus,T. confusum, andT. castaneum.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.640

出版商:Oxford University Press    

年代:1995

数据来源: OUP