摘要:

AbstractSixth stadium nymphs of the grasshopperSchistocerca americana(Drury) (Orthoptera: Acrididae) were presented with spinach with or without added cholesterol or β‐sitosterol, and the lengths of the first four meals were monitored. Spinach alone evoked a typical aversion learning pattern in which successive meals were of decreasing duration; however, when cholesterol or β‐sitosterol was added the spinach remained acceptable. Nymphs fed spinach for 24h preferred glass‐fibre discs with added cholesterol in a choice test, but nymphs fed wheat (an acceptable food) did not prefer cholesterol‐treated or control discs. Nymphs pretreated with spinach did not distinguish between discs treated with stigmasterol (an unsuitable phytosterol for grasshoppers) and control discs. In no‐choice tests, nymphs pretreated with spinach also fed significantly longer on discs with added 10% cholesterol or 1%β‐sitosterol, compared to meals on discs with stigmasterol or sucrose controls. Detection of appropriate sterols is likely to involve a post‐ingestive feedback mechanism, as significantly longer meals on discs treated with only sucrose resulted when spinach‐fed nymphs, were force‐fed gelatin capsules packed with β‐sitosterol or cholesterol, compared with stigmasterol. Contact chemoreception is unlikely to play a role in this behaviour, as discs (lacking sucrose) treated with cholesterol, β‐sitosterol, stigmasterol, or a chloroform control, all required similar numbers of contacts be

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00577.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA comparison was made of the EAG responses of males and females ofGlossina morsitans morsitansWestwood,G.austeniNewstead andG.tachinoides, Westwood to various doses of compounds known to be components of ox and buffalo urine fractions which are attractive to tsetse in the field (phenol, 3‐ and 4‐methylphenol, 3‐ and 4‐ethylphenol, 4‐n‐propylphenol, dimethylsulfone). All three species did not respond to dimethylsulfone. The overall responses to the phenolic substances were higher in females than in males inG.m.morsitansand higher in males than in females inG.austeniandG.tachinoides.Response spectra of the species for the phenolic substances suggested thatG.m.morsitansandG. austeniwere most responsive to 3‐ and 4‐methylphenol and 3‐ethylphenol, whereasG. tachinoideswas most sensitive to 3‐ethylphenol and 3‐methylphenol, and only moderately sensitive to 4‐methylphenol.Cross‐adaptation experiments, in which l‐octen‐3‐ol, acetone, 4‐heptanone and 3‐nonanone were also included, revealed that all phenolic compounds stimulated one and the same class of receptors, which differed from the class of receptors activated by l‐octen‐3‐ol. The ketones also had their own receptors. Hence, the flies can obtain information about the presence of attractants by at least three different receptor classes. It was concluded that phenol and any individual alkylphenol found in ox and buffalo urine should be attractive to tsetse flies, provided that stimulus intensity is above threshold and not beyond optimum. One class of receptors may respond more strongly in males than in females, whereas another class is more responsive in females than in males. This may result in a change in sex ratios in

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00578.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe optomotor yaw response of the desert locust,Schistocerca gregaria(Forsk.), was investigated under open‐ and closed‐loop conditions. When flying tethered in the centre of a vertically striped hollow sphere, the polarity of response of the locust was always the same as the stimulus. The response, therefore, appears suitable to stabilize body posture against passive rotations around the yaw‐axis in free flight. Responses were induced by contrast frequencies up to 150 Hz with a maximum of amplitude at about 20 Hz. The characteristic curve, measured between 0.3 and 160 Hz, is widened up towards higher frequencies as compared with those of bees and flies.Variability was the most striking feature in the locust's yaw response. The amplitude of modulation not only varied greatly between individuals but also changed with the same visual stimulus in the course of an experiment. We therefore suppose that the locust's turning behaviour is subject to gain control mechanisms and that spontaneous gain modulations are responsible for the observed variability in the stimulus‐response con

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00579.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe pre‐calling period (PCP), between emergence and first release of pheromone, determines the number of nights over which femaleMythimna separata(Walker) (Lepidoptera: Noctuidae) can express their migratory potential. In its seasonal migrations in eastern Asia, this armyworm penetrates to latitudes at which it is unable to over‐winter but at which reliable photoperiodic and temperature cues anticipate the deterioration of conditions. The effect of these environmental factors on PCP was examined in moths descended from samples collected in Nanjing (32oN) during the summer migration. Under LD 14:10h, a reduction in temperature, from 23oC during larval development to 18oC from 24 h after pupation, resulted in a twofold increase in PCP compared with insects held at 23oC. At 23oC, short days (LD 12:12 h) extended PCP but the magnitude of the response was increased under a regime of decreasing photoperiod, from LD 15:9h, to LD 12:12 h through larval, pupal and adult development. Further experiments demonstrated that the response depended on a decrease in photoperiod from pre‐pupal stage to adult emergence (the pupal period is spent below ground). A reduction of 50–60min over the 13–15 day pupal period at 23oC was effective. The significance of decreasing photoperiods, irrespective of absolute levels, as a cue for species whose migrations traverse substantial ranges of latitude is considered and the results are discussed in relation to the genetic determination of PCP inM.separataand to its seasonal migrations in east

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00580.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe cell membranes of the corpora allata of the cockroachDiploptera punctatacontain voltage‐dependent calcium channels. Depolarizing current injection into cells of the corpora allata in the presence of the calcium channel blockers, cadmium, cobalt or verapamil allows the production of multiple action potentials, as does treatment with the intracellular calcium chelator, BAPTA/AM. These results suggest that calcium currents are involved both in decreasing the excitability and in activating an outward current in cells of the corpora allata. Electrophysiological measurements also suggest a concomitant reduction in outward conductance following the multiple action potentials produced in the presence of the channel blockers or BAPTA/ AM. We hypothesize that the calcium current may play an important role in the regulation of intracellular calcium concentration and Juvenile Hormone biosynthesi

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00581.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe rotation of the flagellum of male and femaleAedes aegypti(L.) was measured in a wind tunnel at wind speeds between 0 and 116cms‐1. Although the surface area of the female flagellum is only 10% of the male, it rotates through double the angle of the male flagellum for the same increase in wind speed. The larger rotation of the female flagellum could result from: a reduced resistive torque in the flagellar‐pedicellar suspension; a larger antennal‐positioning reflex; a smaller initial angle of attack. The resistive torque in the flagellar‐pedicellar suspension was measured in both male and femaleAedes aegypti.In ten adult females the average torque at 8orotation was 2.70 ± 1.33 times 10‐10Nm and in ten males it was 6.46 ± 3.46 times 10‐10Nm. The significance of these results is discussed with reference to the sexual dimorphism in the sensory tasks required of Johnston's organ in

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00582.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA cluster of five to seven AKH‐like immunoreactive cells lie in each lobe of the paired corpora cardiaca of the true armyworm,Pseudaletia unipuncta.These cells form a mesh work of immunoreactive processes within the corpora cardiaca, and immunoreactive tracts projecting posteriorly over the aorta.Reversed‐phase high performance liquid chromatography of extracts of the corpora cardiaca ofP.unipunctarevealed a single large U.V. absorbent peak with a retention time identical to syntheticManduca‐AKH. Amino acid analysis of the contents of this peak yielded a composition identical to that of syntheticManduca‐AKHwhich was analysed in a parallel manner. Furthermore the material within the peak possessed adipokinetic activity when bioassayed in day 2 adult maleP. unipuncta.The corpora cardiaca of similar individuals were found to contain approximately 17.6ng (17.6pmol) of Manduca‐AKH equivalents per pair.Injection ofManduca‐AKHinto 2‐day‐old adult maleP.unipunctaresulted in a dose‐dependent elevation in haemolymph lipid levels with a maximum level of 80–90μmg/μl obtained with 5–10 ng ofManduca‐AKH.Continuous flight also elevated haemolymph lipid levels in day 4 adult males with a significant elevation evident in the first samples taken after 15 min of flight and lipid levels plateauing at approximately 100 μg/μ

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00583.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe relationship between diapause‐associated metabolic suppression and carbohydrate metabolism linked with cold tolerance was investigated in pupae ofPieris brassicaeL. Cold tolerance was assessed by measuring the crystallization temperature (Tc) and by estimates of pre‐freeze mortality. Metabolic suppression was measured using31P nmr and carbohydrates by GLC.Sorbitol (a possible cryoprotectant) accumulated from the onset of diapause in October until December reaching a concentration ofc.40 mMolal in both years of the study, but then declined from January until adult eclosion in May. TheTcremained between ‐23 and ‐25oC throughout the winter except for a slight rise before eclosion in May. The absence of a significantTcsuppression is as predicted from the low concentration of sorbitol accumulated. The pre‐freeze mortality experiments indicate that pupae are most cold tolerant in the period December‐February when sorbitol concentration is high, suggesting an alternative cryoprotective role for sorbitol. Glycogen declined at the beginning of diapause until February after which there was some recovery suggesting that it may be the source of carbon for sorbitol synthesis.Diapause‐associated metabolic suppression is evident in the low31P nmr resonances of ATP during November‐February compared with non‐diapause pupae and diapause pupae soon after pupation. The suppression of metabolism at this time may have a direct role in cryoprotection and by itself (rather than sorbitol) account for the increased pre‐freeze cold tolerance. ATP appears to increase slowly from February until a sharp increase occurs shortly before eclosion. Arginine phosphate remains high during diapause until late February‐March when it begins a decline which continues until eclosion. A period of change in energy and carbohydrate metabolism is apparent at the same time which may indicate diapause termination and related changes in cold tolerance mechanisms.It is argued that inP.brassicaesorbitol accumulates as a result of metabolic suppression and may have no cryoprotective role. However, for species living in, or colonizing, low temperature environments it is a short evolutionary step to exploit this pathway and accumulate high concentrations of polyols as a specialized co

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00584.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractPheromone glands of the female mothHelicoverpa (Heliothis) armigeraand Malpighian tubules of the locustLocusta migratoria migratorioides(R&F) retained partial biological activity after eryopreservation. Pheromone glands were frozen to ‐70oC in a tissue culture medium (TC‐199) containing 10% of the cryoprotectant dimethylsulfoxide. Malpighian tubules, however, required initial preincubation for 24 h in a medium of high osmolarity before being frozen to ‐70oC in the presence of 10% of the cryoprotectant glycerol. After rapid thawing of both organs, biological activity was compared with the respective fresh organs. Using a radiochemical assay, it was shown that previously frozen pheromone glands were stimulated by pheromone biosynthesis activating neuropeptide to the same degree as fresh pheromone glands. In addition, previously frozen Malpighian tubules were stimulated by an extract of corpora cardiaca to produce c‐AMP to the same extent as fresh Malpighian

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00585.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe body temperatures of six apterous species of Namib Desert tenebrionid beetles were measured continuously with indwelling thermocouples under laboratory conditions and in the field. The range of body temperatures selected was within the upper half of their ‘tolerated range’, which we defined as the temperatures lying between measured critical thermal maximum and critical thermal minimum. In the field, individuals also maintained their body temperatures within the upper half of the ‘tolerated range’. These beetles maintained higher body temperatures than those recorded for any other ectothermic insect. Three of the six species maintained lower body temperatures in the field than they selected in the laboratory. The other three species showed no significant difference between field and laboratory body temperatures. We conclude that these beetles are not forced by biotic or abiotic factors to adopt thermal niches which present them with physiological diffi

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1991.tb00586.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY