摘要:

In laboratory choice tests, maize weevils,Sitophilus zeamaisMotschulsky, initially preferred lower humidities when given a choice of two humidities. The absolute difference in humidities and position on the RH scale had little influence on the response. After 24 h, weevils generally were hygropositive, which suggests that starvation or desiccation or both moderated humidity preference. The same temporal response pattern was observed when weevils were given a choice of five humidities ranging from 0 to 100%. Weevils showed a pronounced preference for contact with tactile stimuli (glass beads) and apparently preferred contact with smaller beads (4 mm diameter) over larger beads (6 mm diameter). Superimposing humidity and tactile stimulus choices revealed that tactile preferences took-precedence over humidity preferences. The nature of the humidity response suggests that poor feedback exists between humidity perception and atmospheric water needs.

DOI:10.1093/ee/20.5.1433

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Previous studies demonstrated that larvae from an Indian strain (S) of the seed beetleCallosobruchus maculatus(F.) are much more competitive than larvae from a Nigerian strain (I) during both intra- and interstrain competition in a small host seed (mung bean). The competitive superiority of the S strain was Similarly evident when two larvae cooccurred in a larger host species (adzuki bean) that represented a novel host for both strains. If one or both larvae within a seed belonged to the S strain, survival to adult emergence was 50% lower than it was in the absence of competition. In contrast, survival decreased by only 15% when two I-strain larvae shared a seed. In head-to-head encounters between strains, most seeds produced a single survivor, and nearly 75% of adults from such seeds belonged to the S strain. Reciprocal crosses suggested an additive genetic component to these differences in competitive ability; the reduction in survival following competition was intermediate among F1progeny. In contrast, the genetic basis of strain differences in adult weight was largely nonadditive, with hybrid progeny displaying a strong dominance deviation toward the heavier S strain. Differences in competitive ability were therefore independent of differences in body size between strains. Variation in competitive ability may ultimately be a consequence of variation in the sizes of host seeds typically encountered by beetle populations.

DOI:10.1093/ee/20.5.1438

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Daily thermoperiods of 27–18° C (square wave) induced diapause inMicroplitis croceipesin continuous darkness, whereas diapause was inhibited in continuous light. Scotophase temperatures were more important than photophase temperatures in diapause induction when photophase was held constant and scotophase increased (increasing light-to-dark ratio). Conversely, when scotophase was held constant and photophase was increased, diapause decreased. This suggests that the ratio of light to dark may be critical in diapause induction ofM. croceipes. In addition, diapause induction increased when low temperature coincided with the scotophase of the photoperiod.

DOI:10.1093/ee/20.5.1444

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Feces that contained residues of digested dairy feed supplements were offered as ovipositional substrates to cagedMusca sorbensWiedemann to determine preference. Results showed preference for residues of digested ground corn. Ovipositional preference for residues of digested ground corn over those from coarser rolled corn suggested a relationship between surface areas exposed to digestive fluids and intensity of ovipositional preference. Feces of cows that were fed complete rations formulated without corn were ovipositionally unattractive to cagedM. sorbens.

DOI:10.1093/ee/20.5.1447

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Sex pheromone production in females of the corn earworm,Helicoverpa zea(Boddie), starts with the onset of scotophase and when the titer of the pheromone reaches ≍30 ng (usually within 30 min), females start calling. Brief exposure of scotophase females to light increased calling significantly, with a corresponding decrease in pheromone titer. Females in photophase can produce pheromone if injected with the pheromone biosynthesis activating neuropeptide (PBAN), but the titer declines rapidly after 1 h. The titer continues to increase in scotophase females for 4 h. The observed lack of pheromone production at low temperatures (14°C) is probably attributable to inhibition of PBAN release and to lower pheromone biosynthetic activity.

DOI:10.1093/ee/20.5.1451

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Testes from progeny of irradiated maleHelicoverpa zea(Boddie) were dissected and examined cytologically to identify the larval stage or age that would ensure the presence of primary spermatocytes undergoing meiotic division and to determine the lowest dose of radiation necessary to induce visible chromosomal aberrations in 100% of the larvae. Results from this study revealed that cytological examination of chromosomal aberrations could be accomplished best when the larvae were 3- or 4-d-old fifth instars. The percentage of F1and F2males with visible chromosomal aberrations was dependent upon the dose of radiation administered to the P1male. A 6-krad dose was sufficient to induce visible aberrations in all F1larvae. Chromosomal aberrations were observed less frequently in F2larvae than in F1larvae.

DOI:10.1093/ee/20.5.1457

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Conidium germination and differentiation ofZoophthora radicanson water agar were investigated to identify requirements for the production of appressoria, the structures needed for virulence. Appressorium formation was more sensitive to environmental and nutritional changes than was conidium germination. Temperature affected both formation of germ tubes and appressoria, and the best temperature–nutrient interaction was found for appressorium formation at 25–30°C and 1% yeast extract. At 15°C, conidium germination was depressed independent of the nutrient concentration, and appressoria did not form. The volume of liquid overlaying the conidia and the yeast extract concentration individually affected appressorium formation. The best interaction between the volume of liquid and yeast extract concentration was the combination of a large volume of liquid medium (3 ml/962 mm2surface area) and 1% yeast extract. Of the 12 nitrogen sources tested, the best for germination and appressorium formation were yeast extract and Bacto-Soytone. Glucose, maltose, and starch were the best of the 12 carbon sources tested. Increasing osmotic pressure caused by different concentrations of maltose and polyethylene glycol adversely affected formation of germ tubes and appressoria. Subculturing did not affect formation of germ tubes, but the frequency of appressorium formation decreased after 12 transfers. The best pH for appressorium formation was between 7.0 and 7.2.Z. radicansproduced appressoria on cuticles of deadEmpoasca fabae(Harris) nymphs at 25°C in the dark.

DOI:10.1093/ee/20.5.1460

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The effect of fruit species on parasitization ofAnastrepha ludens(Loew) byDiachasmimorpha longicaudata(Ashmead) was studied. The roles of fermenting fruit volatiles, size, and color in host habitat selection by this parasitoid also were investigated. The lowest percentage parasitism was recorded for larvae in grapefruit,Citrus paradisiMacf. On the other hand, grapefruit volatiles and size proved most attractive toD. longicaudata. Greater percentage parasitism was recorded for larvae in smaller and apparently less attractive fruit. The length of the parasitoid's ovipositor, depth of the fruit pulp, and host larval behavior could explain these contrasting results. Citrus volatiles attracted almost twice as many female parasitoids as volatiles of mango,Mangifera indicaL., or peach,Prunus persicaL. Fruit>5 cm in diameter were equally attractive toD. longicaudata. Selection of colors byD. longicaudatawas not statistically different among colors tested.

DOI:10.1093/ee/20.5.1469

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Consumption of nuclear polyhedrosis virus-infected prey—larvae of the soybean looper,Pseudoplusia includens(Walker)—by the predatorNabis roseipennisReuter variously affected development, survival, and reproduction of the predators. Nymphs fed infected prey larvae developed significantly faster at 25°C than nymphs fed uninfected prey. Nymphal survival was not affected by prey infection. Preoviposition periods were significantly longer for predator females maintained on infected prey throughout their lives than for those receiving uninfected prey during preimaginal or adult (or both) stages. Daily rates of oviposition were highest for females that received uninfected larvae as their nymphal diet, regardless of adult diet. In contrast, total fecundity was greatest for females receiving uninfected prey as adults, regardless of the nymphal diet. The nymphal diet, however, affected total fecundity of females. Consumption of infected larvae by adult predators significantly reduced their longevity, irrespective of the nymphal regimen.

DOI:10.1093/ee/20.5.1475

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

A new multiple embedded nuclear polyhedrosis virus was isolated from a fourth-instar celery looper,Anagrapha falcifera(Kirby) collected from cabbage in central Missouri in May 1985. Characterization and comparison to other multiple embedded nuclear polyhedrosis viruses via restriction endonuclease analysis indicated a unique baculovirus with a molecular weight of 85.6 × 108Daltons. This baculovirus (AfMNPV) was propagated in cabbage looper larvae and tested against a variety of insect species in laboratory bioassays. More than 31 species of Lepidoptera from 10 families demonstrated susceptibility when allowed to feed ad libitum on substrates (artificial or natural) contaminated with occlusion bodies (OB) at 10 or 100 OB/mm2.Helicoverpa(=Heliothis) zeaandH. virescensdid not demonstrate differential susceptibility to AfMNPV (LC50, 0.36 and 0.39 OB/mm2, respectively) as compared to the alfalfa looper,Autographa californica, multiple embedded nuclear polyhedrosis virus (AcMNPV) LC50, 10.3 and 0.45 OB/mm2, respectively). No other currently known natural or genetically engineered baculovirus infects as many cosmopolitan, economically important insect species or causes mortality as quickly at low concentrations. This is the first baculovirus patented by the U.S. Government Patent and Trademark Office (no. 4,911,913, issued 27 March 1990).

DOI:10.1093/ee/20.5.1480

出版商:Oxford University Press    

年代:1991

数据来源: OUP