摘要:

The microarthropod and enchytraeid fauna of a natural lead-contaminated soil in a Norwegian spruce,Picea abies(L.) Karst., forest was studied in gradients from unpolluted soil to the middle of a vegetation-free area. Because of dissolved lead from the bedrock, about 50 m2of the forest floor lacked vegetation, and another 50 m2had weakly developed vegetation. The lead content in the raw humus was up to 10–15% dry wt. Increasing levels of lead gave a gradual reduction in species numbers among plants and microarthropods. Microarthropod species varied in their ability to live in lead-polluted soil. Four groups were recognized: (1) sensitive species associated with normal vegetation, (2) less sensitive species occurring even in areas with strongly reduced vegetation, (3) tolerant species extending their range into vegetation-free areas, and (4) microarthropods favored by strong lead pollution (Isotoma olivaceaTullberg among Collembola andNanorchestessp. among mites). Because a few species increased strongly in the vegetation-free area, the total abundance of microarthropods remained almost the same throughout the gradient. Changes in vegetation cover along the lead gradient is a confounding factor, but sensitive species proved to react equally negatively to increased lead levels when the vegetation factor was kept constant. Possible adaptations to lead during the postglacial period are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1263

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Laboratory studies showed that the soybean phytoalexin glyceollin, an isoflavonoid previously investigated as an inhibitor of fungal pathogens, is an effective antifeedant for some insect species. Glyceollins extracted from soybean,Glycine maxMerrill, cotyledons were applied to the surface of common bean leaves,Phaseolus vulgarisL., in five concentrations, including physiological concentration, for feeding preference tests. Leaves treated with glyceollin at concentrations below physiological levels were less acceptable to the southern corn root worm,Diabrotica undecimpunctata howardiBarber, and the Mexican bean beetle,Epilachna varivestisMulsant, than untreated leaves. Feeding deterrence was positively correlated with increasing concentrations. The bean leaf beetle,Cerotoma trifurcataForster, was not affected even by very high doses. An ethological concentration (EC50) was computed based on the log dose–reduction of acceptance of treated disks. The EC50for the Mexican bean beetle was 6.1 μg/mg leaf dry weight and 3.5 μg/mg for the southern corn rootworm. Results indicate that soybean phytoalexins may represent a common defense against microorganisms and insect herbivores.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1278

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Microscopic analysis of gut contents of freshly caughtLytia politaSay usually revealed an abundance of pollen exclusively from the genusPinus. The overwhelming preference of these blister beetles for staminate pine cones was confirmed in laboratory feeding trials. Body water content in wildL. politawas significantly greater than in laboratory-rearedEpicauta pestiferaWerner, a meloid used as a reference (71 versus 52% total mass, respectively), but the two species contained equivalent amounts of hemolymph (27% total mass). These results were surprising because staminate pine cones eaten byL. politawere very dry in comparison with the artificial diet ofE. pestifera(33 versus 83% total mass, respectively).L. politabeetles readily drank water in the laboratory, so in the wild they probably gain water by ingesting rain or dew.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1283

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Olfactory responses of lesser cornstalk borer,Elasmopalpus lignosellus(Zeller), larvae to conspecific individuals and peanut plant parts were determined in olfactometer studies. Larvae were not attractive to conspecifics. Young peanut pods infested by two larvae had the same attractiveness as intact pods. Peanut roots, pegs, and pods attracted significantly more larvae, although there were some differences in attraction between lesser cornstalk borer instars. Roots and young pods attracted more small and large larvae. More medium larvae were attracted to pegs and roots. Olfactory responses of larvae to peanut roots were eliminated after antennae were treated with N-methylmaleimide (1 mg/ml in 100% ethanol). There were no differences between the responses of untreated larvae and those with only the palpi blocked. Larval olfactory response to peanut plant volatiles therefore depends primarily on the antennae.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1289

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Preferential selection of fecal pats for oviposition byMusca sorbensWiedemann from cows fed different rations was studied. Caged ovipositingM. sorbenswere overwhelmingly attracted to feces from cows fed concentrated feed supplements over feces from cows fed only grass. Gravid flies showed restraint in ovipositing on feces from cows fed on grass when confined in insect cages for protracted periods with no other breeding media available. Weight of fly puparia reared from preferred feces was 46.7% greater than that of puparia from feces ignored by ovipositing flies at the same dairy. Fresh samples of cow fecal pats were classified as either attractive or unattractive to ovipositingM. sorbensbased on the presence or absence of egg clusters and were analyzed for differences in crude protein content. Results showing similar crude protein content in both samples indicated that protein residues were not responsible for ovipositional preference. These studies suggested that (1)M. sorbensrefrains from ovipositing unless specific odors from digestive residues of concentrated feed supplements in cow feces are present; (2) fecal odors attracting ovipositingM. sorbensare related to nutritional needs of fly larvae; and (3) odors from digestive residues other than protein may be responsible for this attraction.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1296

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Corythucha cydoniae(Fitch), a serious pest of rosaceous hosts, did not diapause when reared in the laboratory at 20.6, 26.1, and 31.7°C in a photoperiod of 14:10 (L:D). A polynomial regression showed that egg development across temperatures was nonlinear ranging from 10 d at 31.7°C to 19 d at 20.6°C. Instar development for both sexes was similar at each temperature, and development was linear. At all temperatures, third instars required the least time for development and fifth instars required the most. Males, both single and paired, outlived females at all temperature regimens. At 20.6°C, single males lived a maximum 286 d and paired males 289 d; corresponding female cohorts lived a maximum 167 d and 140 d, respectively. Fecundity varied nonlinearly with temperature and was highest at 26.1°C, with a mean of 322 and 369 eggs produced by mated and unmated females. This previously reported univoltine species was determined to be trivoltine in Maryland. Feral adults demonstrated diapaused-like behavior in mid-September. Also, adults reared as nymphs in a glasshouse with natural, declining light diapaused with a delayed preoviposition period; whereas adults from nymphs reared in the lab under 14:10 (L:D) did not diapause. High fecundity, trivoltinism, absence of significant parasites and predators, and a wide host range contribute to the pest potential ofC. cydoniae.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1299

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Mated female papaya fruit flies,Toxotrypana curvicaudaGerstaecker, oriented to and contacted single immature papaya fruit presented in an experimental arena and exhibited a rhythmic up-and-down movement of the head (bobbing) after initial contact with the fruit. Such bobbing, with the proboscis contacting the fruit surface at each bob, always preceded probing and puncturing of the fruit with the ovipositor. Forty-eight percent of 25 females tested probed within 5 min; 11 of these laid an average of 29 eggs per oviposition bout, which lasted an average 20.5 min. Withdrawal of the ovipositor was followed by ovipositor grooming and extensive continuous sponging of the fruit surface with the proboscis. During observations of female papaya fruit flies on fruit in a commercial papaya planting, all of these types of behavior were observed. Using the same laboratory experimental design, a combination of color (green), shape (wax disks and domes), and chemistry (solvent extract of papaya peelings) was required to obtain rates of contact similar to those obtained with immature fruit. However, oviposition was not obtained using such combinations of artificial stimuli. In a flight tunnel, mated females were attracted to immature papaya fruit and to the odor of papaya fruit piped into the tunnel indicating that host odor is used in long-range orientation to host plants and fruit.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1305

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Survival of reciprocal populations of European corn borer,Ostrinia nubilalis(Hübner), equaled or was intermediate to natural populations and an introduced low-diapause population (exotic), which survived less well. When peak natural second-generation hatch (31 July–3 August) north of 39°00′ N lat. was approximated, most of seven natural populations approached 100% diapause. However, only 0.25–22.95% of the exotic population diapaused. Diapause by progenies of reciprocal crosses was greatly influenced by this exotic parent. At the most northern locations, Ankeny, Iowa, and St. Paul, Minn., influence of the parental male was particularly evident. When peak natural third-generation hatch (13–16 August) south of 39°00′ N lat. was approximated, five reciprocal populations diapaused similarly to their corresponding natural populations (≈85%). Late-season hatch allowed larval diapause of the exotic population to increase to 46%. Under these late-season conditions, influence of the parental male was evident only at the most southern locations, Portageville, Mo., and Tifton, Ga. This apparent contradition of parental male influence between midsummer and late-summer hatch is because heterogeneity for diapause remains in a low-diapause population. Introductions of a low-diapausing population north of 39°00′ N lat. during late July apparently encourage resultant progeny from reciprocal crosses to avoid larval diapause and to perish in late autumn.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1311

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Aphidophagous coccinellid beetle populations were sampled by sweep net from 1969 to 1985 in small grain fields in eastern South Dakota. The assemblage of coccinellids consisted of six species:Hippodamia eonvergensGuerin-Meneville,H. tredecimpunctata tibialis(Say),H. parenthesis(Say),Coleomegilla maculata(DeGeer),Coccinella transversoguttataFaldermann, andCycloneda munda(Say).H. convergenswas the most abundant coccinellid, followed byH. tredecimpunctata,H. parenthesis,Coleomegilla maeulata,Coccinella transversoguttata, andCycloneda mundain rank order of abundance. Seasonal patterns of population increase differed among species. At all sites, populations of each species fluctuated unpredictably among years and independently of populations of other species. Assemblage structure at a site changed unpredictably from year to year, but the extent of change was constrained. Averaged over years, there were distinct differences in the structure of coccinellid species assemblages at geographically separated sites. Although assemblage structure varied from year to year at a site, there was no evidence of systematic change in structure at any site over the years of the study. A technique was proposed for evaluating the effect of introduced predators on coccinellid species assemblages.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1320

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A variety of factors were investigated to determine their influence on the epizootiology of the nuclear polyhedrosis virus (NPV) of the gypsy moth,Lymantria disparL. Egg masses laid on tree boles had substantially higher levels of contamination than those laid on rocks, ground debris, or understory brush. Egg masses laid on different tree species showed no differences except that those on black oaks were less contaminated at one of the three research sites. Egg mass contamination was not related to date of collection, compass orientation, or number of larvae hatched from the egg mass. Larvae collected from pitch pine had higher infection rates than those from either white or black oaks; however, the differences were not substantial. Mortality rates of larvae collected from different host species were even less distinctive. The implications for epizootiology and sampling are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1330

出版商:Oxford University Press    

年代:1990

数据来源: OUP