摘要:

Queens ofSolenopsis invictaBuren, the red imported fire ant, that were collected following mating flights raised their first workers in the laboratory. Colony members were counted, queens were weighed, and all were marked with paint. Eighty-four colonies were randomly paired and the pairs were placed adjacent to one another and their behavior observed. At 4 d, 23 of the colonies had combined to form two-queen colonies, the other 19 formed single-queen combined colonies. At 60 d, 38 of the colonies had combined to form single-queen combined colonies. Queens that produced the greater number of brood survived in combined colonies. Colony raiding was the method observed for combining colonies. Supernumerary queens were eliminated by abandonment or attack by other queens or workers. Minims eliminated or abandoned the queens that produced fewer worker brood. Colony raiding may be an adaptive method of increasing colony size and vigor.

DOI:10.1093/ee/20.4.1037

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The influence of defoliation on gypsy moth fecundity and male moth wing length and the relationship between male moth wing length and egg mass density were investigated. Male pupae and egg masses were collected from plots located in the leading edge area of the gypsy moth infestation in Virginia and Maryland. Defoliation and egg mass density estimates were made in each plot. Male pupae were allowed to emerge, and the left forewings of 2,636 moths were measured to determine wing length. Fecundity was determined volumetrically for 767 egg masses. Gypsy moth fecundity and male wing length decreased substantially only when defoliation exceeded a threshold level of ≍40%. There was a minimal change in fecundity and male wing length due to increasing levels of defoliation above or below this threshold. Thus, the effect of defoliation on male wing length and fecundity is essentially binomial (i.e., male wing lengthy is either large or small and fecundity is either high or low). Wing length of male moths explained only ≍10% of the variation in egg mass density in the area where pupae were collected. The wing length of moths captured in pheromone traps used in conjunction with the number of moths captured may be useful for monitoring gypsy moth populations.

DOI:10.1093/ee/20.4.1042

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The Mediterranean fruit fly,Ceratitis capitata(Wiedemann), was reared at three larval densities in ripe mock orange,Murraya paniculata(L.), obtained from five locations in the field. Larvae and preadult survival decreased with increase in larval density.C. capitatafield infestation rates varied between locations from 0.5 to 148.4 larvae/kg of fruit. MoreDacus dorsalisHendel were reared from field collected fruits thanC. capitata. The weight of mock orange fruit varied between locations from 0.31 to 4.0 g/fruit. Survival and reproduction parameters are discussed in relation to availability of fruit in the field. We conclude that the availability of ripe mock orange fruit in the field ultimately influences the number of fruit flies that survive to the next generation.

DOI:10.1093/ee/20.4.1048

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Bephratelloides cubensis(Ashmead), a seed-feeding wasp, is the primary pest of annonas in Florida. The weekly infestation rates of commercially grown sugar apples (Annona squamosaL.) and atemoyas (A. squamosa×A. cherimolaMiller) byB. cubensisin southern Florida were monitored. Infestation generally increased throughout the summer in atemoyas but remained very low in sugar apples. The observed patterns are attributable to the relative fruiting phenologies of the commercial species and of the overwintering host, the bullock's heart (A. reticulataL.). We found no evidence that diapause ofB. cubensisin atemoya and sugar apple fruits is of economic importance as an overwintering mechanism in Florida.

DOI:10.1093/ee/20.4.1053

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

In controlled environment studies the effect of plant water stress on the life history characteristics of the potato leafhopper,Empoasca fabae(Harris), was examined for insects on early regrowth and bud stage alfalfa (Medicago sativaL.). On both plant growth stages, the developmental period of male and female nymphs increased with the increase in plant water stress. Although the differences were relatively small, the stressed treatments were significantly longer than the well-watered control. Plant water stress did not influence nymphal mortality at either plant growth stage. Adult survivorship was lower on the water-stressed treatments, except for females on early regrowth alfalfa. Fecundity declined with the increase in plant water stress, particularly for insects reared on bud stage alfalfa. Oviposition rates during the first half of adult life declined with the increase in plant water stress, but this relationship was not found for the gross reproductive rate. The long-term effect on reproduction of nymphal development on water-stressed alfalfa was examined by switching recently emerged adults from stressed to well-watered hosts. The oviposition rates of these females remained below that of the control for most of the subsequent six 2-d oviposition periods. These changes in the life history traits of the potato leafhopper indicate that water-stressed alfalfa is unfavorable for leafhopper population growth. This decline in suitability may result from the lower nitrogen content of water-stressed alfalfa or to changes in other components of host quality.

DOI:10.1093/ee/20.4.1058

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The majority of life history traits of the egg, nymph, and adult stages of the potato leafhopper,Empoasca fabae(Harris), are adversely affected when they use water-stressed alfalfa (Medicago sativaL.). The consequences of these changes at the population level were examined by constructing life history statistics for cohorts on well-watered, moderately, and severely stressed alfalfa at the early regrowth and bud stage. The net reproductive rate declined with the increase in plant water stress for cohorts on both plant growth stages. The intrinsic rate of increase (rm) decreased when expressed on both a day and a degree-day basis. On early regrowth alfalfa,rmvalues on a centigrade degree-day basis were 0.0064, 0.0049, and 0.0039 for the control, moderate, and severe treatments, respectively. On bud stage alfalfa,rmvalues were 0.0049, 0.0041, and 0.0031 for the same treatments. The higher temperatures found in water-stressed fields were insufficient to compensate for the lowerrmof populations in these treatments. Coupled Leslie matrices were used to model the growth of leafhopper populations during one alfalfa growth cycle. These simulations show a 41 and 54% decline in total population size at harvest for the moderate and severe treatments, respectively. Data from water-stressed field plots were used to validate results from the controlled environment studies. Similar responses were found for immature developmental period, adult fecundity, and nymph population size. These results indicate that data obtained at a relatively constant water potential in a controlled environment can be used to approximate those values under the more variable conditions found in the field.

DOI:10.1093/ee/20.4.1067

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The simulation model (MiteSim) of the mite predator-prey system consisting of Banks grass mite,Oligonychus pratensis(Banks), and the predatory miteNeoseiulus fallacis(Garman) was used to evaluate mite population dynamics in Nebraska corn fields in relation to microenvironmental variables. Simulation results demonstrated the importance of using humidity and temperature conditions at the leaf surface instead of weather station conditions to simulate the mite system on corn in Nebraska. Also, humidity (in addition to temperature) was determined to be critically important in the population dynamics of the two mites. The temperature and humidity at the leaf surface of moderately drought-stressed corn (compared with well-watered corn) resulted in higher simulated populations of Banks grass mite. Simulation studies also showed that colonization of a corn field by less than one adult female Banks grass mite per plant in June can result in mite densities sufficient to cause crop loss by August (Banks grass mite biotic potential without extrinsic mortality).

DOI:10.1093/ee/20.4.1074

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The development, population dynamics, and predation on the eggs and first instars of the house fly,Musca domesticaL., by the manure-inhabiting beetleCarcinops pumilio(Erichson) were simulated in a computer model. Model features include: nonlinear development of beetles and flies, fecundity as a function of beetle density, and predation rate as a function of beetle and fly density. All these processes depend on temperature, which can be set to a constant value or read from a file of variable temperatures. The model includes a management component that incorporates the effects on house fly and beetle populations of various insecticide and manure-removal strategies for fly control. Examples of the results of simulating various management regimes are presented.

DOI:10.1093/ee/20.4.1079

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Offspring of overwintering femaleTyphlodromus pyriScheuten were reared on leaf disks and fed larvae of European red mite,Panonychus ulmi(Koch). In this study,T. pyrinymphs killed fewer prey than didT. pyriin other studies where the predators were reared on artificial substrates such as gelatin capsules. Nymphs showed a type II functional response to prey density: as prey density increased, kills increased at a decreasing rate to a plateau of three to four prey per day. Maximum rates of kill were a quadratic function of temperature over the range 18–26°C. There were significant differences between the sexes in feeding rates but not in rates of development. Rates of development of eggs and larvae and from egg to adult were an exponential function of temperature. Nymphs that ate less than one prey per day had reduced rates of development and survival. Individuals not given any prey survived only a few days as protonymphs. The susceptibility of nymphs to food shortages emphasizes the importance of alternative sources of food (pollen, fungi, other mites) toT. pyriwhen spider mites are scarce. Temperature responses of this Canadian strain ofT. pyridiffered from responses reported in western Europe: rates of development from egg to adult were higher at temperatures20°C.

DOI:10.1093/ee/20.4.1089

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The suitability of Garry oak (Quercus garryana) and red alder (Alnus rubra) as hosts for the gypsy moth,Lymantria dispar(L.), was assessed under laboratory conditions by observing larval survival, larval weights, foliage consumption, developmental period, pupal weight, and ova production. Survival was not significantly different between larvae fed Garry oak (98.7%) or red alder (97.4%). The mean maximum live larval weights were significantly different between sexes but not between diets. Females weighed 2,498 mg when fed Garry oak and 2,210 mg when fed red alder. Males weighed 894 mg when fed Garry oak and 737 mg when fed red alder. The mean amount of foliage consumed was significantly different between sexes but not diet. Female larvae consumed an average of 705 cm2of Garry oak and 678 cm2of red alder foliage. Male larvae consumed 247 cm2of Garry oak and 253 cm2of red alder foliage. The mean time from egg hatch to pupation was significantly different between sexes and diets. Female larvae pupated in 39.5 d on Garry oak and 48.1 d on red alder. Male larvae pupated in 33.4 d on Garry oak and 40.6 d on red alder. Pupal weights were not significantly different between sexes or diets. Male pupae weighed 554 mg from a larval diet of Garry oak and 572 mg from red alder. Female pupae weighed 1,846 mg from Garry oak and 1,711 mg from red alder. An average of 863 ova (Garry oak) versus 758 ova (red alder) was present in the reproductive tract of 2-d-old females, an insignificant difference. Pupal weights, frass production, and ova production were highly correlated. Nutritional indices indicated that Garry oak foliage was converted into biomass slightly more efficiently than that of red alder. These data indicated that foliage of either Garry oak or red alder provided a very suitable diet for the gypsy moth.

DOI:10.1093/ee/20.4.1097

出版商:Oxford University Press    

年代:1991

数据来源: OUP