摘要:

A potential problem exists when rate (1/time) is used for parameter estimation instead of time in least-squares estimation of nonlinear development models, because the squared error is the quantity that is minimized by this technique. Minimizing the squared error in the rates is not equivalent to minimizing the squared error in time. This is of particular significance in modeling insect development because, when development times are largest, rates are small and squared errors in the rates produce large errors in time predictions. The purpose of this study was to show that, in many cases, parameters should be evaluated in terms of the observed data. Using least-squares techniques on rates did not allow for the minimization of the absolute squared error in time at low temperatures. Least-squares techniques applied to development time produced good predicted values throughout the temperature range in particular cases. These results show that when parameters are not evaluated in terms of the observed data but rather in some modified form such as rate, erroneous predictions may result.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.484

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Susceptible ‘Newton’ and resistant ‘Abe’ winter wheat (Triticum aestivumL. em Thell.) were infested with larvae of biotype E Hessian fly,Mayetiola destructor(Say). Plants and crowns of infested ‘Newton’ weighed less, were shorter, had fewer tillers, and had significantly less soluble carbohydrates than the control plants. Only the plant height of infested resistant ‘Abe’ was significantly reduced. This finding was unexpected because avirulent larvae have never been shown to affect the growth of a resistant host. In ‘Newton,’ only the quantity of sucrose differed between treatments, being significantly greater in the infested than the control plants, although there was a trend for the control plants to have more fructan and less sucrose, glucose, and fructose than the treated plants. No differences were noted in soluble carbohydrates between infested and control ‘Abe.’ Ancymidol, a plant growth retardant, stunted both wheat cultivars but did not alter resistance in ‘Abe.’ Gibberellic acid (GA3) reversed ancymidol-induced growth inhibition but did not reverse Hessian fly stunting in ‘Newton.’ Therefore, stunting of wheat by the Hessian fly and ancymidol treatments appear to involve different biochemical pathways.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.489

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Stethorus punctum(LeConte) is an obligate predator of tetranychid mites. Laboratory studies examined the proportion of time beetles spent searching, feeding, and resting when adult females and third instars encountered an abundance of all instars of the tetranychid miteTetranychus urticaeKoch. Preference for various prey instars, relative handling times, and the influence of starvation on these behaviors were determined. Satiated female beetles spent 45.1% of their time searching, 14.4% feeding, and 40.5% resting. Female beetles that were starved spent a greater proportion of time feeding, with an increase in handling time per prey. The increase in handling time was due to a more complete extraction of body fluids from individual prey. Female beetles preferred mite eggs, and that preference was not significantly altered by starvation. Satiated larvae spent 78.4% of their time searching and 21.6% feeding; they did not spend any measurable amount of time resting. Starvation of larvae significantly increased the percentage of time spent feeding and the handling time per prey. Third instars preferred nymphal mite stages to other instars, and this preference was not significantly altered by starvation. The results are discussed in reference to predator–prey dynamics.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.494

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The effect of irrigation on diversity and density of foliage-inhabiting arthropods was determined for late maturity, wide row soybean during a three-year study in the alluvial plain (Delta) in Mississippi. The ratio of amount of rainfall in dryland soybean to amount of irrigation and rainfall in irrigated soybean (“stress index”) ranged from 0.11 to 0.54, with canopy development reduced at the sites where rainfall was most limiting. Herbivore species richness was greater and predator evenness lower in irrigated than in dryland soybean at the most severely stressed site. The ratios of density of total arthropods, herbivores, and predators in dryland to irrigated soybean were positively correlated with the stress index over the three years of the study. Of the most common species, all showed similar response (as did order totals and trophic levels), exceptHeliothisspp. and bigeyed bugs,Geocorisspp., which were equally or more abundant in the dryland than in the irrigated soybean. Establishment of damsel bugs (Nabisspp.) occurred after the canopy from adjacent rows overlapped. In the final year, early initiation of pivot irrigation resulted in earlier canopy development and was associated with synchronization of density of damsel bug nymphs and lepidopterous larvae in pivot-irrigated, but not in furrow-irrigated or dryland soybean.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.498

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Existing quantitative palynological techniques (i.e., chemical processing, counting, and numerical analysis of pollen) were adapted for use by entomologists. Particularly important were calculation of pollen concentrations and assessment of pollen volume. Corbicular pellets, honey, larval pollen provision masses, and feces contained pollen exines representative of plants visited by bees. Dietary importance of a plant was assessed from a number of pollen grains and volume. Counts of small pollen grains represented dietary importance adequately (i.e.,LarreaandAmbrosia), whereas counts of large grains (i.e.,CereusandAcacia) underrepresented dietary importance. Data were presented in graph form and reliability was demonstrated from samples repeatedly drawn from a thoroughly mixed honey bee pollen diet. Corbicular pellets were collected fromApis mellifera(L.) colonies fitted with Ontario Agricultural College pollen traps during 1985 in Pima Canyon, near Tucson, Ariz.; 25 species were present. Results from a bee diet include pollen grains of diverse morphologies and volumes, stressing the importance of adequate sample preparation, chemical processing, and numerical analysis. Use of these methods by apiculturists and melittologists will facilitate direct, justifiable comparison of pollen diets for bees.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.507

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Bean leaf beetle,Cerotoma trifurcata(Forster), adults were sampled from 1986 through 1988 in soybean and alfalfa in central Iowa to ascertain the seasonal phenology of this pest. Data from all 3 yr indicate that two generations of this insect occur in Iowa. Overwintering adults inhabit alfalfa before soybean emergence, colonize soybeans immediately after seedlings emerge, and die by late June. F1adults are abundant from late June to middle or late August, and F2adults are present from early August to soybean maturation. Females are more abundant than males among overwintering and F1adults, but neither sex of F2adults is more numerous. The yellow/red adult ratio is greater during the fall than in the spring, indicating greater winter survivorship of red adults. Adults were present in soybean from seedling emergence to crop maturation but were found in alfalfa only in late spring, before soybean emergence, and in August–September as soybean matured. Captures of adults during diurnal sweepnet collections made from 0830 to 2030 hours (CST) on 21 July 1988 were least at 0830 and 1000 hours, the period of heavy dew on the soybean canopy. From 1300 to 1600 hours, the number of females with developing ovaries declined, whereas the number of females with fully developed eggs increased.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.514

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Males of eight species of clearwing moths were collected in pheromone-baited traps placed in commercial nursery, urban, and forest habitats in eastern and middle Tennessee during 1987 and 1988. Seasonal flight activity was recorded forPodosesia syringae(Harris), lilac borer;Paranthrene simulans“palmii” (Grote), an oak borer;Synanthedon scitula, dogwood borer;Synanthedon rhododendri(Beutenmüller), rhododendron borer;Synanthedon exitiosa(Say), peachtree borer;Synanthedon fatiferaHodges, a viburnum borer;Synanthedon acerni(Clemens), maple callus borer; andSynanthedon decipiens(Hy. Edwards), a borer of cynipid galls on oak. The dogwood borer exhibited bimodal emergence with the first peak occurring in mid-May and the second in the beginning of August. In the forest, the rhododendron borer exhibited bimodal emergence. The dogwood borer and peachtree borer were not collected in the forest habitat.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.520

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

In western Maryland, the European corn borer,Ostrinia nubilalis(Hübner), exhibited three flight periods (from late May to mid-September 1986–1988) but completed only two generations in corn. Oviposition by corn borer moths increased when the tassels emerged and shed pollen. Peak density of the predatorsOrius insidiosus(Say) andColeomegilla maculata(DeGeer) coincided with peak density of the borer's second-generation eggs and neonates. Second-generation egg masses and second and older instars were randomly distributed between plants in the field where first instars were aggregated. Corn borer females of the second flight period deposited most eggs (82%) on the ventral surfaces of leaves in the middle sections of plants near silking ears (76.7%). The emerging neonates initially dispersed randomly on the leaves. However, 30 min after emergence, most neonates cued on leaf axils, which served as the most common microhabitat for young larvae. Larval microhabitat differed substantially between the nonoverwintering and overwintering forms and between early and late instars of the nonoverwintering form. Leaf axils were the preferred microhabitat of young larvae, but preference shifted to stalks and ears as larvae matured. Overwintering larvae inhabited almost only stalks. Similarly,O. insidiosusadults and nymphs changed their within-plant distribution throughout the season. These changes in the distribution of borer larvae and their predators are discussed in relation to prey and pollen availability in different corn plant microhabitats.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.526

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Seasonal activity of the European alder leafminer,Fenusa dohrnii(Tischbein), onAlnuswas examined at Midland, Mich., and Rhodes, Iowa. Oviposition activity, adult trap catch data, and leaf-mining activity all indicated the presence of three generations of leafminer per year. Changes in population levels seemed to correspond with weather phenomena, especially rainfall. The presence of five feeding instars was confirmed.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.534

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Overwintering sites and spring emergence periods of three commonly occurring coccinellids were studied from 1984 to 1989 in the upper coastal plain area of South Carolina. In addition, experiments were conducted to determine the influence of temperature and photoperiod upon the feeding activity of overwinteringHippodamia convergens(Guérin-Méneville) when removed from hibernation sites. Feeding activity began shortly after removal from hibernation, increased with increasing temperatures and continued during both the photoperiod and the scotoperiod. Broomsedge,Andropogon virginicumL., was found to be an important overwintering site forH. convergens. Coleomegilla maculata(De Geer) andCoccinella septempunctataL. often shared the same overwintering habitat. Spring emergence of all three species was found to be controlled by temperature and all species began emergence at ≈50DD accumulated degree-days, with the emergence period extending from about the first week of March to the middle of April. A tendency for directional flight upon emergence was shown by all three species, with significantly moreH. convergensandC. septempunctataflying to the east and south sides of the emergence cages, which was with the prevailing winds during the emergence period.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.540

出版商:Oxford University Press    

年代:1991

数据来源: OUP