摘要:

Studies were conducted to determine nature and amount of morphometric variability within the greenbug,Schizaphis graminum(Rondani), in an effort to further understand biotypes of this species. Data on morphometrics of the four morphs (males, apterous/viviparous, apterous/oviparous, and alate/viviparous females) were pooled for three biotypes (B, C, and E) and various multivariate statistical analyses were performed. The data suggested that the three biotypes formed significantly different groups. The four morphs were also significantly different from each other. When morphs and biotypes were considered simultaneously, the canonical discriminant analysis grouped greenbugs of different morphs into four different, well-isolated clusters. Within each cluster, individuals of each biotype were further grouped into small subclusters. The Mahalanobis distance analysis suggested that biotype E is closely related to biotype C. The distance analysis also indicated that biotype C is closely related to biotype B. Similar Mahalanobis distance analysis also suggested a close association between apterous females and alate females, as stated in the literature.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.839

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Adult Diptera burn sugar fuels at high rates in their flight motors, and most species require external sources of sugar for normal longevity. Flower nectar is usually assumed to be the main fuel source in nature. However, honeydew produced by various Homoptera is the primitive external sugar-fuel source for Diptera, and it is still a main source for many species. The pseudotracheate labellum is a “ground-plan” feature of Diptera that originated as an adaptation for obtaining sugars from honeydew. It enables flies to dissolve dry foods and then suck up the resultant fluid under cover of the labellar lobes. The labellum, thus, prevents significant water loss during feeding on dry foods. It is particularly well suited for obtaining sugars from the dried, thin films of Homoptera honeydew. The hypothesis that Diptera originally depended on honeydew explains their “dancing” behavior; their attraction to small, shiny objects; the presence of sugar receptors on their tarsi; and various basic, primitive differences between Diptera and other orders of Neoptera. These ideas are in agreement with the fossil record of Diptera and Homoptera. Homoptera were abundant in the Permian; the first undisputed Diptera appeared after the Permian in the Triassic. Flowers did not appear until much later (in the Cretaceous). The labellum gave adult Diptera access to honeydew sugars early in their evolution and enabled them to retain a more thoroughgoing aerial life.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.847

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Microplitis rufiventrisKokujev (Hymenoptera: Braconidae) was imported from Cairo, Egypt, into the United States, where it developed successfully in the corn earworm,Heliothis zea(Boddie); the soybean looper,Pseudoplusia includensWalker; the beet armyworm,Spodoptera exiguaHübner; the fall armyworm,Spodoptera frugiperda(J. E. Smith); the cabbage looper,Trichoplusia niHübner; the black cutworm,Agrotis ipsilon(Hufnagel); and the tobacco budworm,Heliothis virescens(F.). Mean developmental time from oviposition to adult was 13.6–15.6 d at 28°C depending on host species.P. includensyielded the highest percentage of female progeny; however,H. zeaandS. frugiperdawere preferred hosts in laboratory tests utilizing these three hosts. The parasitoid successfully searched in field cages forH. zea, P. includens, andS. frugiperdafeeding on soybeans. Incidence of parasitism reached 95% ofS. frugiperdaandH. zeain field cages.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.855

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Interactions between infestations of onion thrips,Thrips tabaciLindeman, the three growth stages of onion (prebulbing, bulbing, and sizing), and onion yield were investigated in field and greenhouse experiments. Significant negative correlations existed between thrips numbers and yield only during bulbing, although percentage of yield reduction varied considerably between studies. During bulbing stage, a 2–3% yield reduction per 10 thrips was obtained for two field studies. Under greenhouse conditions, 10 thrips per plant resulted in a 7% yield reduction. In an additional study, plants were mechanically defoliated at 0, 30, and 60% levels during the three onion growth stages. This also resulted in yield reduction following damage during bulbing stage.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.859

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Interactions of a biological agent,Trichosirocalus horridus(Panzer), with a commonly used herbicide for thistle control, 2,4-dichlorophenoxyacetic acid (2,4-D), were examined using the thistle weevil's response to low-level 2,4-D sprays on two species of thistles at different growth stages, and thistle response to 2,4-D and weevil infestation. Two hundred sixty transplanted thistle rosettes of two thistle species at three developmental stages, naturally infested withT. horriduslarvae, were randomly selected in spring; half were sprayed with 15% of the recommended field dosage of 2,4-D. Plants caged 2 d later yielded a total of 2,246 weevils within 10 wk. Number of adults emerging from sprayed plants was less than half of that from unsprayed plants. Plant age or growth stage affected time and level of adult emergence, and thistle species affected level of emergence. Yield of adults from plants sprayed with 2,4-D, however, was not different from yield derived from healthy plants of the less-preferred thistle species or developmental stage. Combination ofT. horridusinfestation and the reduced dosage of 2,4-D caused 85% thistle mortality compared with 7% mortality in unsprayed weevil-infested thistles and 55% mortality in weevil-free rosettes sprayed with the reduced dosage of 2,4-D.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.864

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Reemergence and emergence ofIps avulsus(Eichhoff) andIps calligraphus(Germar) were studied in twelve loblolly pines,Pinus taedaL. Reemergence peaked at 22.2–42.2% of the infestation time span forI. avulsusand 25.5–44.7% forI. calligraphus, depending on bole height. Reemergence continued up to 60% of the infestation time forI. avulsusand 63.8% forI. calligraphus. Seventy-five percent of the attackingI. avulsusand 64% of the attackingI. calligraphusreemerged. Emergence began at 31.1–53.3% of the infestation period forI. avulsusand 51.1–68.1% forI. calligraphus, depending on bole height. Emergence resulted in a per-capita production of 1.41 and 1.43 brood beetles per adult beetle forI. avulsusandI. calligraphus, respectively. Brood survivorship averaged 13.6% forI. avulsusand 4.5% forI. calligraphus. A three-parameter nonlinear function was used to describe reemergence and emergence in relation to time. The proportion of maleI. avulsusto total reemerged and emerged beetles was 0.467 and 0.476, respectively. The proportion of males forI. calligraphusreemergence and emergence was 0.278 and 0.480. For both species, higher proportions of males reemerged early followed by increasing proportions of females. During emergence, females were in higher proportions early, followed by increasing proportions of males.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.869

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

The aphid parasite,Aphelinus perpallidus(Gahan), was exposed to different densities, (0.125, 0.25, 0.50, 0.75, and 1.0 aphids per cm2)of its host,Monellia caryella(Fitch). Aphid density and fecundity of unmated and matedA. perpalliduswere significantly related. Mated females produced both male and female offspring, whereas unmated females produced only males. Adult parasite emergence was not significantly affected by host density. There was no significant difference in emergence between mated and unmated females. Significantly more male parasites emerged at all densities. Parental age of unmated or matedA. perpallidusfemales did not significantly affect parasite fecundity or emergence. Fecundity and emergence were significantly higher with unmated females. Mated females produced significantly more male progeny. These data indicate that matedA. perpallidusfemales from 0 to 14 d old must be used and exposed to aphid density levels of 0.50–0.75 aphids per cm2to obtain enough parasitism in order to have higher production of female progeny.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.877

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Seeds of peas and legumes attracted more ovipositing females of the bean seed maggot (BSM),Delia florilega(Zetterstedt), than seeds of cucurbits and corn. A bacterium,Pseudomonassp., and a yeast,Cryptococcus laurentiivar.laurentii, isolated from squash seeds and cultured on squash-seed-exudate agar, stimulated BSM oviposition. More eggs were laid between 1200 and 1800 hours, but some oviposition occurred at all hours. Mean fecundity was higher at 20°C (192.6 eggs per female) than at 25 or 30°C, but the percentage of fertile eggs was highest at 25°C. At 20°C, mean longevity was 58.9 and 46.4 d for females and males, respectively. Eggs hatched at all temperatures tested (5–40°C). At 25°C, 90.0% of the eggs hatched and 81.0% of these larvae pupated; however, at 5 and 40°C, only 8.6 and 50.0% hatched, respectively, and resulting larvae did not complete development at these temperatures. Larvae reared at 10 and 15°C entered pupal diapause. At constant temperatures, averages of 31.6, 219.9, and 236.8 degree-days were required for egg, larval, and pupal development above threshold temperatures of 6.4, 5.6, and 4.6°C, respectively, and 486.5 degree-days were required for development from egg to adult above an average threshold of 5.2°C.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.881

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Phytophagous insects representing seven orders, 38 families, and 91 species, 19% of which were economic pests of crops, fed onBaccharis neglectaBritt. (Compositae) in Texas. About 58% of the species were polyphagous, 13% were restricted to the Compositae, and 7% were monophagous onBaccharis. B. neglectawas a host during the dry season (June–September) for ca. 50 species of foliage- and sap-feeding insects. Pollinating insects representing 46 species, 25 families, and four orders visitedB. neglectaduring flowering in the fall.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.887

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Taylor's power law, Iwao's patchiness regression, and the negative binomial distribution with a common value ofkwere used to model variance/mean relationships of populations of four species of cereal aphids,Schizaphis graminum(Rondani),Macrosiphum avenae(F),Rhopalosiphum padi(L.), andRhopalosiphum maidis(Fitch), occurring in winter wheat and spring oat fields in South Dakota. Taylor's power law generally provided a better model of variance/mean relationships than did the other models. Intercepts of Taylor's power law regressions (loga) varied among populations of some cereal aphid species occurring on different host crops. Regression slopes (b) generally did not differ among populations inhabiting different crops; however,bdid differ among populations ofR. padisampled from spring oats and winter wheat. Power-law parameters were independent of field and year at which populations were sampled and time during the growing season at which samples were taken. These results suggest that marked changes in environment (e.g., different host crops) influenced spatial distributions of cereal aphid populations and, hence, the value of power-law parameters. However, for populations inhabiting either host crop, power-law parameters seemed to be independent of temporal and spatial variation.

ISSN:1754-5692    

DOI:10.1093/ee/16.4.896

出版商:Oxford University Press    

年代:1987

数据来源: OUP