摘要:

Flight behavior of the specialist parasitoidMacrocentrus grandiiGoidanich to olfactory stimuli from corn, the principal food plant of its host, European corn borer,Ostrinia nubilalis(Hübner), was studied in a wind tunnel. Extracts of corn volatiles, isolated using Tenax, elicited Right initiation, upwind anemotaxis, casting, landing, and ovipositor unsheathing behaviors inM. grandii. Flight responses were dependent on certain plant- and parasitoid-related factors. Leaf and husk volatiles were attractive, while kernel, silk, and tassel volatiles were not. Similar responses were exhibited to volatile extracts from leaves of plants at 2-leaf, 12-leaf, and tassel stages of development and to those of field- and sweet-corn cultivars. Flight response to isolated corn volatiles was gender and age specific. Males and newly emerged females were not attracted. After 4 d, Right response in females increased with age. Attraction was also enhanced after females were provided the opportunity to oviposit in corn-fed European com borers possibly through the process of associative learning. The results of this study suggest that corn volatiles have potential for use for increasing parasitism of European corn borer byM. grandii. However, certain plant- and parasitoid-related factors that influence flight behavior ofM. grandiineed to be considered while developing the technique for application in the field.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1448

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The predation ecology of the striped lynx spider,Oxyopes salticusHentz, and green lynx spider,Peucetia viridans(Hentz), was studied during 108 h of visual observation in an insecticide-free cotton field in central Texas. Evidence obtained during this study indicates that lynx spiders were the dominant arthropod predators (among 134 cases of arthropod predation observed, 94 were attributable to lynx spiders).P. viridansis a powerful species (10.08 ± 0.52 mm [mean ± SEM] body length) compared with the significantly smallerO. salticus(4.24 ± 0.16 mm). TheO. salticusindividuals fed on small-sized prey (2.41 ± 0.17 mm average prey length). In contrast, theP. viridansindividuals fed over a broader range of prey size classes and captured a higher proportion of the larger prey organisms (7.04 ± 0.73 mm average prey length). However, the smallestP. viridans(≤ mm spider length) and the largestO. salticus(≥4.5 mm spider length) selected prey of similar average length (=3 mm). The lynx spiders are polyphagous insectivores that feed on a variety of prey species predominantly in the insect orders Heteroptera, Hymenoptera, and Diptera. They also frequently eat other spiders. The most frequently captured prey ofO. salticuswere small Heteroptera (predominantly cotton Aeahopper,Pseudatomoscelis seriatus[Reuter]), whereasP. viridansmost frequently seized large stinging Hymenoptera (e.g., honey bee,Apis melliferaL.). The degree of the feeding specialization of the two spider species was mathematically assessed (niche breadth coefficients) and statistically compared; computed coefficients indicate thatP. viridansis a significantly more polyphagous predator than the smaller-sizedO. salticus.O. salticus, therefore, shows a better fit to the “model predator” of classical biological control because of its relative specialization.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1457

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Laboratory, greenhouse, and field studies were conducted to determine whether the eggs of southern corn rootworm,Diabrotica undecimpunctata howardiBarber, from adults that had fed on a bitter (cucurbitacin C-containing) cucumber variety experience less predation than eggs from beetles that had fed on a nonbitter (noncucurbitacin C-containing) cucumber variety. Human taste tests and insect bioassays indicated the presence of cucurbitacin in the “bitter” eggs. Eggs from adults that had fed upon bitter and nonbitter cucumber cotyledons and early foliage were placed into soil at three different distances from one another and at four different density combinations of bitter:nonbitter eggs. There were no significant differences in predation of eggs by any of the four arthropod predators tested caused by cucumber variety or by egg distance and density. In a laboratory experiment, eggs from adults feeding on bitter and nonbitter cucumber varieties were compared for percentage egg hatch without moisture stress (held at 100% RH) or stressed for 6, 12, or 18 h at 94% RH before being held at 100% RH. Bitter eggs in both unstressed and stressed for 6 h treatments hatched significantly earlier than nonbitter eggs. There was no significant difference in hatched rate between bitter and nonbitter eggs stressed for 12 or 18 h. The presence of cucurbitacin C does not appear to protect southern com rootworm eggs from predation by the arthropod predators tested compared with nonbitter eggs. However, more rapid development and earlier eclosion of bitter eggs relative to nonbitter eggs may help bitter eggs survive in soils that fluctuate between dry and moist conditions.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1466

出版商:Oxford University Press    

年代:1992

数据来源: OUP

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1475

出版商:Oxford University Press    

年代:1992

数据来源: OUP

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1479

出版商:Oxford University Press    

年代:1992

数据来源: OUP