摘要:

Median development rates of larvae (LDR) and pupae (PDR) of wild housefly,Musca domesticaL., were measured by rearing larvae in poultry manure at 12.4, 17.3, 23.1, 32.0, and 38.9°C at densities of 1, 2.5, and 5 larvae per g of manure, and by rearing pupae at 13.7, 17.1, 23.0, 31.8, and 37.0°C. Manure temperature, larval density, and their interaction significantly influenced median LDR (range, 0.0477–0.1667). Larval survival was affected by density and manure temperature. Median PDR (range, 0.0417–0.2916) and survival in pupae was a response to air temperature but not the level of crowding preceding pupation. Predicted development rates correlated with observed rates for each larval density (R2= 0.964, 0.958, and 0.979 for 1, 2.5, and 5 larvae per g manure, respectively) and for pupae (R2= 0.999). However, these rates differed by 3–16% among larval densities within temperature which corresponded to variations in development time of 0.5–3.8 d. The relationship between cumulative numbers of larval–pupal transitions and the physiological age of flies was influenced at the 5th and 25th percentiles of the population by larval density and at the 75th and 95th percentiles by larval density and manure temperature. The relationship for pupal–adult transitions was influenced only by air temperature.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.971

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Surveys ofAnopheleslarval habitats in northern Belize were carried out during September 1990 and April 1991. At each site, larvae were collected and the physical and chemical characteristics of water and species composition of aquatic vegetation were measured or estimated. Data on presence or absence of four species,Anopheles albimanusWiedemann,A. creciansWiedemann,A. pseudopunctipennisTheobald, andA. argyritarsisRobineau-Desvoidy, were used for analysis of associations with environmental factors, habitat types, and regions. Using significantly contributing environmental variables, discriminant functions (DF) were constructed for theAnophelesspecies, except forA. argyritarsiswhose distribution could be predicted solely by altitude. The stability of DFs was checked by cross-validation runs. The DF forA. pseudopunctipenniswas 93% accurate in predicting positive habitats. Predictions based on DFs forA. albimanusandA. crecianswere 74 and 80% accurate, respectively. Of the fourAnopheles species present in the study area,A. albimanuswas the most common. Together withA. crecians, it occurred mostly on the coastal plain, and both species were present in both wet and dry seasons.Anophelesalbimanuswas positively associated with cyanobacterial mats and submersed-periphyton habitat types and negatively associated with the filamentous algae habitat type.A. crecianswas positively associated withEleocharis-periphyton habitat type.A. pseudopunctipennisandA. argyritarsiswere common only during the dry season and their distribution was limited to the Karst and Mountain Pine Ridge regions. Both species were positively associated with the filamentous algae habitat type, andA. argyritarsiswas also positively associated with the rock pools habitat type. Physical factors (e.g., water depth, water temperature, and oxygen content) were usually marginally correlated with larval occurrence. Dominant plant growth forms, such as filamentous algae, cyanobacterial mats, and submersed macrophytes showed the closest association with the larvae of particularAnophelesspecies. Our results demonstrated the controlling influence of dominant aquatic vegetation on larval presence.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.978

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

A study was conducted to determine the effects of grasshopper density and plant composition on grass growth and destruction by the mixed grass- and forb-feedinggrasshopper,Melanoplus sanguinipes(F.). Using a completely randomized design, 125l-m2cages were placed on plots on mixed-grass rangeland in western South Dakota and stocked with 0, 5, 10, 15, or 20 fifth-instarM. sanguinipes. Grasshopper densities within the cages were monitored approximately weekly, and total grasshopper feeding-days were calculated for each cage for 68 d. Before adding grasshoppers, biomasses of grasses and forbs within the cages were estimated visually and after 68 d, final biomass of vegetation was determined. Results from analysis of variance with regression and multiple regression analysis indicated that grasshopper density and the initial biomass of western wheatgrass and shortgrasses within the cages significantly affected the final biomass and growth of western wheatgrass and the amount of grass removed by grasshoppers. However, significant reductions in grass biomass occurred only in cages stocked with 15 and 20 insects, equivalent to 845 and 1,112 grasshopper feeding-days, respectively. Grasshopper density had no significant effect on biomass of shortgrasses and Japanese brome, although growth of these species was affected by initial biomass of grasses in the cages.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.993

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

We searched for effects of diflubenzuron treatment on numbers and diversity of two groups of litter arthropods—spiders (Araneae) and orthopteroid insects (Orthoptera and Dictyoptera)–in a West Virginia hardwood forest infested with gypsy moth. We established sampling stations consisting of pitfall traps in treated and untreated plots(four each) and sampled for up to 75 d following spray. Variability in dependent variables(habitat differences) was reduced by performing principal components analysis on habitat variables and by introducing the principal components into the treatment effect models as covariates. A treatment effect was apparent from 21 to 42 d after spray in both spider and orthopteroid insect abundance, although the effect was significant on only two sample dates for orthopteroid insects. There was no treatment effect on species diversity for these two groups.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1003

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The effects of oviposition behavior ofCallosobruchus chinensis(L.) on life table statistics of progeny and on attack by the larval ectoparasitoidAnisopteromalus calandrae(Howard) were studied. As the number of eggs per seed increased, larval development time and survival rate decreased. Differences in mortality between treatments was caused largely by competition in the late instars. Life table statistics showed an inverse linear relationship to the number of eggs per seed. Depositing one egg per seed increased progeny production by ≈56% compared with six eggs per seed. The functional response ofA. calandraeshowed a linear relationship with host density in the range of 1–64 per 100 seeds. The parasitoid searched for its hosts more efficiently when the number of eggs per seed increased from one to four; search rate of the parasitoid based on random search increased from 0.045 ± 0.013 (mean ± SEM) to 0.154 ± 0.025. The results indicate that ovipositing fewer eggs per seed is also a good defense tactic for the weevil against the parasitoids. Whether parasitoids or larval competition selected the oviposition behavior is not yet clear. However, the influence of natural enemies should be studied further to understand the evolutionary process of the weevil's oviposition behavior more precisely.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1009

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Developmental time, fecundity, nymphal mortality, generation time, intrinsic and finite rates of increase, and days for population to double were compared for peaaphid,Acyrthosiphon pisumHarris, feeding on cover crop seedlings of sesbania,Sesbania exaltata(Rafinesque-Schmaltz) Cory; cowpea,Vigna unguiculata[L.] Walpers; hairy indigo,lndigofera hirsutaL.; hairy vetch,Vicia villosaRoth; crimson clover,Trifolium incarnatumL.; or cereal rye,Secale cerealeL. The study was conducted under constant temperatures (15, 20, 25, and 30°e) in the laboratory.A. pisumhad the shortest developmental, prereproductive, and generation times onV. villosaandT. incarnatum, followed byV. unguiculata. However,A. pisumhad higher mean total fecundity, fecundity rate, and intrinsic and finite rates of increase onV. villosaandT. incarnatumthan on other cover crops evaluated. Differences in life parameters ofA. pisumwere detected on the same plant species exposed to different temperatures. Probing behavior of individualA. pisumdiffered on various cover crops. Mean probe duration was longer onS. exaltataandI. hirsuta, whereas the time to start the first probe, the number of probes per 6-min observation period, and nonprobing duration were shorter onV. villosaandT. incarnatumthan on other plant species evaluated.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1016

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

We conducted a series of field experiments to assess whether cool-season grasses were important in maintaining populations of the Russian wheat aphid,Diuraphisnoxia(Mordvilko), between the summer harvest and fall sowing of winter cereals. All six grass species in a common garden in northern Utah supported aphid population growth from May to September 1991, although aphid densities were unusually low on mature foliage in July. Under conditions of little or no plant competition, each grass species produced at least a few fall tillers before mature shoots had senesced completely and hence provided a continuous source of food for aphids. Indian ricegrass was a consistently good host and bluebunch wheatgrass was a consistently poor one, but the relative suitabilities of the six hosts varied considerably over the season. Neither plant water content nor total nitrogen was correlated with differences in aphid performance among hosts. We conducted a greenhouse experiment to compare estimates of plant quality under field and greenhouse conditions. Differences in aphid perfornlance among hosts in the greenhouse resembled those observed in the field early in the season, but not during the critical “oversummering” period.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1022

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Vertical transmission studies of aNosemasp. infecting a grasshopper,Chorthippus curtipennis(Harris), were conducted in the laboratory. Mated pairs of field-collected grasshoppers were allowed to oviposit, and the adults and progeny were subsequently examined for infection. Infection status of the parents had no effect on fecundity. A preliminary analysis of observed differences in percentage hatch was also not significant, but further analysis suggested that there were differences between mated pairs. The analysis suggested that some of the differences in hatch rate were caused by infection of the female when mated pairs were subsequently classified as having a high or low hatch rate. Vertical transmission was maternally mediated, with>70% of the progeny infected at5 d after hatch.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1031

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The effects of selected prey species on life history characteristics ofLyctocoris campestris(F.), a predator of stored-product insects, were examined in the laboratory at 30 ± 1°C, 70 ± 5% RH, and 16:8 (L:D) h. Newly emerged nymphs (n = 40) were reared singly on each of eight prey species and followed through all life stages until the predator died. Prey consisted of final instars of test species that were killed by freezing. Life table statistics were used to compare the predator's potential dynamics on different prey regimes. Developmental period of nymphs was the longest (27.8 d) onTrichoplusia ni(Hübner), a nonstored-product pest, followed byTrogoderma variabileBallion (25.7 d),Rhyzopertha dominica(F.) (25.3 d),Oryzaephilus surinamensis(L.) (24.8 d),Lasioderma serricorne(F.) (24.3 d),Plodia interpunctella(Hübner) (22.6 d),Tribolium castaneum(Herbst) (21.8 d), and the shortest onCadra cautella(Walker) (21.6 d), all stored-product pests. The proportion of nymphs surviving to adulthood was also affected by prey species. Prey species significantly affected the preoviposition period of the adult females. The preoviposition period was shortest onP. interpunctella(9.0 d), and longest onT. variabile(16.9 d). Oviposition period did not differ among the eight prey species tested. Total fecundity was higher onC. cautella,P. interpunctella, andT. variabilethan onL. serricorne,T. castaneum,R. dominica, andO. surinamensis; and lowest onT. ni. There was a strong correlation (r = 0.753) between oviposition period and fecundity across all species. Oviposition rate (number of eggs per female/d) was highest onP. interpunctella(4.3), and lowest onT. ni(1.99), giving finite rates of increase (λ) of 1.0757 and 1.0379, respectively. Life table statistics showed thatP. interpunctella,T. castaneum,C. cautella, andL. serricornewere the most suitable prey forL. campestris, followed byT. variabile,O. surinamensis, andR. dominica, withT. nileast suitable.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1035

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Sweetpotato whitefly,Bemisia tabaci(Gennadius), was sampled on peanuts during 1991 and 1992 in Alachua County, FL, to determine parasitoid abundance and levels of parasitism. Common parasitoid species ofB. tabaciin 1991 wereEncarsia nigricephalaDozier,Encarsia pergandiellaHoward, andEretmocerus californicusHoward.E. nigricephala, E. pergandiella, andE. transvena(Timberlake) were the most abundant parasitoid species in 1992, whereasE. californicusappeared only rarely.E. nigricephalawas the most common species in both years and accounted for 91% of adult parasitoids reared from whitefly-infested foliage in 1991, and for 54 and 71% of parasitoids reared from foliage at two sites in 1992.E. pergandiella,E. californicus, andE. transvenawere more common during the late season, whereasE. nigricephalawas most prevalent during the early season. Parasitism contributed significantly to whitefly mortality und, in 1992, 90% of all fourth instars were parasitized by 10 September at the second site and by 21 September at the first site. Vertical distribution within plants of sweetpotato whitefly stages, unparasitized and parasitized, was assessed in 1992. Red eye nymphs (late fourth instar) were most common on leaves 4, 5, and 6 (from the top of a lateral stem), and 91% were located on the lower leaflet surface. Parasitized fourth instars were most prevalent on leaves 5, 6, and 7 and were found on the lower leaflet surface 79% of the time. All life stages were equally distributed among the four leaflets of the compound leaf. These data indicate that monitoring for whitefly parasitism in peanuts could best be accomplished by examining both surfaces of a leaflet picked from the fifth leaf down from the terminal lateral stemleaf. The conservation of parasitoids to increase natural biological control of sweetpotato whitefly in peanuts is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1043

出版商:Oxford University Press    

年代:1993

数据来源: OUP