摘要:

Despite>40 yr of ecological and behavioral research on reproductive interactions involved in sterile insect release programs, experimental measurement of the intensity of intermale competition for mates and the role of sterile females in these programs has rarely been addressed. Experiments described in this study were designed to evaluate these factors. Virgin females from a mass-rearing strain (mass reared for 36 yr) of the Mexican fruit fly,Anastrepha ludens(Loew), were released and subsequently recaptured along with native Mexican fruit flies in natural habitats in Nuevo Leon, Mexico. Tests were carried out at six locations and replicated four times. Recaptured females were dissected to determine mating status. Data were analysed to determine whether the released females mated with native males, and to evaluate the influence of test site, test date, and wild male and female density on rates of recapture of the released females and their mating status. Results showed that 5–50% of the recaptured females mated with native males. This indicates that released females (even from a strain adapted to mass rearing) may occupy a significant amount of native male reproductive effort and that males in native populations have excess reproductive capacity. Number of native males captured per test was significantly correlated with the percentage of mated females. Plots of percent mating versus number of native males captured showed that when number of captured males was high, percent females mated was always high, but when numbers of males captured was low, percent mating could still be high. A severe freeze during the fourth test greatly reduced the native population. Released females were recaptured up to 7 wk after release and 4 wk after the freeze, indicating that the mass-reared strain had sufficient physiological-behavioral tolerance to survive extreme environmental stress.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.294

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Studies were conducted to provide information on the behavior of nymphs and adults of potato leafhopper,Empoasca fabae(Harris), under sudden low-temperature conditions, the host-finding ability of potato leafhopper nymphs, and on the soil cooling rate during freezing and subfreezing temperatures. Avoidance of sudden low temperatures by susceptible life stages decreases low-temperature mortality. The percentage of potato leafhopper nymphs and adults dropping off leaf surfaces when exposed to experimental temperatures of 0, 5, and 10∘C for 1 h were measured. More fourth and fifth instars dropped off the leaves at all three temperatures than did first to third instars and adults. Significantly more insects of all ages dropped off the leaves at 0∘C than at 5 or l0∘C. The percentage of potato leafhopper nymphs relocating host plants at two plant densities were measured. Significantly more insects were found within 15 cm of the release point(s) (37.8%) than were found 15–30 cm (27.0%), 30–45 cm (17.4%), or 45–60 cm (19.3%) from the release point(s). No significant differences were found in host-finding ability between instars. The percentage of nymphs able to relocate host plants ranged from 24 to 27%. Success in host relocation by nymphs was not influenced by host plant density. The cooling rates of soil samples acclimated to 4.4∘C were measured 3.0 cm below the soil surface, on the soil surface, and in the leaf canopy for three experimental temperatures (0, −5, −l00∘C). Leaf canopy temperatures reached 0∘C in 15, 15, and 5 min for the three temperatures, respectively. Soil surface temperatures reached 0∘C in 115, 35, and 15 min, respectively. Soil temperatures at the depth of 3.0 cm did not drop to 0∘C within 3 h under any of the three temperature regimes used in these experiments. Survivorship of potato leafhopper nymphs when exposed to long durations of freezing or subfreezing temperatures may be overestimated when using available low-temperature mortality information without taking into account the insect behaviors and host finding abilities at the low temperatures reported here.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.301

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

A combination detergent wash-optical staining technique was developed to determine the concentration of virus polyhedral inclusion bodies (PIBs) present on samples of common forest substrates. Experiments were performed to determine the efficacy of the procedure for estimating the abundance of applied virus of gypsy moth,Lymantria dispar(L). (Lepidoptera: Lymantriidae), from samples of bark, leaf litter, and soil. Detection and quantification of inclusion bodies present in the wash supernatant was accomplished by staining the inclusion body protein and observing the stained particles using phase contrast microscopy. Positive identification of the virus particles and the determination of virus activity was accomplished through the bioassay of the wash supernatants. The mean recovery rate of virus applied to substrates, after washing and staining, was high (76.5%) but differed between bark (65%), leaf litter (68%), and soil (79%). No difference in recovery rates was detected when different concentrations of virus were applied to the same substrates. Bioassays were performed for virus concentrations ranging from 103to 107PIBs per ml by applying virus directly to artificial diet, and by applying virus to forest substrates, subjecting these substrates to the washing procedure, then applying the wash supernatant to artificial diet. An analysis of covariance was performed on the doseresponse curves of control virus and virus washed from the three substrates. The analysis revealed no significant differences between the two curves, indicating that the washing and staining procedure itself has no effect on virus viability. The optical enumeration technique, therefore, provides a reliable and inexpensive method for the assessment of virus abundance on substrates in the environment.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.307

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The development and survival ofBruchus pisorum(L.) eggs were studied at various constant temperatures from 7.8 to 30.3∘C and at 76 and100%RH to construct a population dynamics model. Eggs were categorized into three morphological stages. The lower temperature threshold for stage 1 was ≤7.8∘C and for stages 2 and 3 was ≍11∘C. The upper temperature threshold was ≥30.3∘Cfor stage 1and 27.9∘C for stages 2 and 3. Stage 3 developmental times were lengthened and survival was reduced by the high relative humidity and artificial hatching substrate (i.e., filter paper versus pea pods). Each stage was described by a curve for the median developmental time-temperature relationship and the temperature-independent distribution of normalized developmental rates. The resultant model was tested by a multiple cohort procedure and a comparison with proportional egg development data colJected in eight plots of field peas from 1986 to 1988. Stage-specific probabilities of survival were kept at 1.0 because of the high field survival, which ranged from 88.7 to 99.2% per plot. By iteratively fitting the initialization values (the estimated frequency distributions of oviposition), a close agreement was achieved between predicted and observed developmental times.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.314

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Frankliniella occidentalis(Pergande), the western flower thrips, is a common pest of greenhouse floral and vegetable crops. Studies in four vegetable greenhouses revealed a significant correlation between density and sex ratio of adults on sticky traps. At low densities, 80–100% of western flower thrips adults on traps were males. As density of thrips within a greenhouse increased, the proportion of females on traps also increased to 60–90%. Predictions about future population dynamics of western flower thrips can be made based on the sex ratio of adults caught on traps. This shift in adult sex ratio can have important consequences with respect to outbreak potential of thrips and damage to greenhouse crops. Laboratory experiments suggest that maternal age and sperm availability influence sex ratio and size of broods produced by individual mated females. Once mated, all females produced female-biased sex ratios ($\bar x$, 67% daughters). When virgin females were exposed to 1, 5, or 10 males for 1 wk, only those with 10 males produced daughters throughout their lifetime (up to 4 wk). These results are discussed with respect to sex ratio theory.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.322

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The western spruce budworm,Choristoneura occidentalisFreeman, was used to test the hypothesis that insect herbivore performance is dependent on dietary nitrogen in a positively linear or convex manner. Artificial diets with seven levels of N were tested both with or without mineral supplements to determine if minerals had important effects on the budworm's response to N. A three-generation bioassay quantified survival rates for all life stages and pupal weights for insects reared on diets with 1.2–7.6% N dry mass. Data were used to estimate population growth over three generations by determining the number of F1F2, and F3offspring produced (i.e., fitness). The budworm's response to increased dietary N was neither positively linear nor convex. Larvae reared on diets with very high (3.9 and 7.6%) concentrations of N, compared with N levels in Douglas-fir,Pseudotsuga menziesii(Mirb.) Franco, foliage, had good survival and reproduction, whereas larvae on diets with N levels near foliage quantities (1.2–3.0%) had very poor performance, with the exception that performance was good on the mineral-limited 1.2% N diet. The addition of minerals to the diets had important effects on responses to N, implicating an interaction between N and minerals. Regression analysis of data on estimated population growth on the 14 diets tested indicated that the ratio of Zn to N was the best predictor of budworm fitness, not the actual N content of the diet. The response to Zn/N ratios was concave, implying proportions ≤0.00085 or ≥0.00282 had positive effects on fitness, whereas ratios from 0.001 to 0.0025 had negative effects. It was hypothesized that host plant N determines the amount of food ingested, which in tum affects the amounts of other nutrients consumed. Thus, a proper balance of many different nutrients appears to be the most important factor in the nutritional ecology of insect herbivores.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.331

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Plant part and girdle associations ofSpissistilus festinus(Say) instars on soybean,Glycine max(L.) Merrill, were investigated by inspecting randomly selected whole plants. Locations of many nymphs changed from stem to nonstem stmctures as plant development increased and later back to stem structures as lateral branches became available. Third to fifth instars preceded first and second instars in these changes. A large proportion (≥39%)of nymphs was associated with main stems regardless of plant phenology. Association of nymphs with plant reproductive structures was least (2%) during blooming and greatest (13%)during pod fill. Association of nymphs with stem and petiole girdles increased with nymphal age. Also, a greater proportion of older nymphs was oriented above girdles. Girdle association was higher for nymphs on leaves and petioles than for those on stems, but most nymphs were not associated with girdles. The absence of differences in associations ofS. festinusinstars with reproductive structures contrasted with the differences observed in associations with girdles, suggesting that the factors responsible for nymphal association with the two types of structures may differ.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.345

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Adult male and female mantids,Tenodera aridifolia sinensisSaussure, exhibited similar dispersal in a large, natural field population. Distance and frequency of movement of bee-tagged individuals was the same for each sex, and neither sex demonstrated a significant directional bias. Therefore, contrary to the findings of an earlier study, females can move as far on the ground as males can fly during their adult lives under natural circumstances. Neither males nor females moved farther than 70 m from the point at which they were originally tagged, which may explain the disjunct local distribution of this geographically widespread, introduced species.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.350

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The influence of the position of egg masses of the gypsy moth,Lymantria dispar(L.), on a tree bole on hatching time was investigated at field sites in Ontario and Pennsylvania. Although eggs were deposited predominantly on the eastern sides of tree boles, egg hatch was most advanced in masses located on southern sides. There was no strong relationship between height on the tree bole and rate of egg hatch, especially for the lower portion (<2m) of the bole. Eggs deposited under bark flaps experienced a significant delay in hatching compared with eggs deposited on the bark surface. Within egg masses, eggs from the bottom third of the mass hatched slightly later than those from the middle or top thirds of the mass. Understanding the microclimatic variables that influence hatch times will improve the accuracy of prediction of the phenology of this forest pest.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.354

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Bemisia tabaciwas collected in the Coachella and Imperial valleys of California and reared on cotton (‘Delta Pine 61’) and cucumber (‘Poinsett 76’) in temperature-controlled cabinets at 20.0, 25.5, 29.0, and 32.0∘C. Data were collected on preimaginal developmental period and mortality. Mean overall developmental periods varied from 38.2 d at 20∘C to 17.4 d at 32∘C. on cucumber and from 28.6 d at 20∘C to 17.7 d at 25SC on cotton. Development was slower at 20.0 and 25.5∘C on cucumber and slower at 29.0 and 32.0∘C on cotton. Immature survival was ≍50% on cotton at all temperatures, and on cucumber increased from 33 to 72% with increasing temperatures. Developmental periods and survival for each preimaginal stage also are presented.

ISSN:1754-5692    

DOI:10.1093/ee/21.2.359

出版商:Oxford University Press    

年代:1992

数据来源: OUP