摘要:

ABSTRACT.This study investigated a possible trade‐off between bark beetle reproductive effort and future survival. Parent adultIps typographus(L.) (Coleoptera: Scolytidae) were collected when they re‐emerged from a laboratory culture after completing their first brood and held at constant temperatures of 4 or 25oC. As a comparison, emerging brood adults were collected and held at 25oC. The longevity of the beetles was related to when they re‐emerged or emerged (measured in days since parent introduction) and to their size (pronotal width), fresh weight and lipid content at collection, by multiple regression analysis. The expression (fresh weight x pronotal width‐2.6), used as an estimate of lipid content of the living beetles, was significantly correlated (r=0.67, P<0.001) with the actual (extracted) lipid content. At 25oC, fat content was the variable most strongly correlated with survival time in all beetle groups except parent females. In both parent and brood females, re‐emergence or emergence day, respectively, contributed significantly to the explanation of survival time, whereas pronotal width and fresh weight never contributed significantly to the regression equation. At 4oC, fat content was not estimated but, re‐emergence day was negatively correlated with survival time. In conclusion, beetles with high fat content and re‐emerging or emerging early have longer expected survival than beetles leaving the log later or containing less fat. This means that females laying a large first brood might suffer a somewhat higher mortality than females laying a

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00915.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.The ability of the acrididSchistocerca americana(Drury) (Orthoptera: Acrididae) to learn to avoid a food when it is associated with an artificial aversive stimulus was examined. The aversive stimulus used was an injection of nicotine hydrogen tartrate at a concentration which usually did not cause knockdown. Insects learned to avoid a food which already had limited sustained acceptability. The learning was not found when the aversive stimulus followed a meal on a fully acceptable food.

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00916.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.. A circuit and accompanying program that allow an inexpensive personal computer to replace an expensive storage oscilloscope in displaying electroantennogram (EAG) recording is described. The maximum amplitude of the EAG is calculated automatically by the computer and appears as an alphanumeric display on the monitor screen. Because the entire EAG trace is stored by the computer, parameters of the EAG trace other than the maximum amplitude are also available for analysis, such as voltages at specified times after antennal stimulation.

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00917.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The spike discharges of the descending contralateral movement detector (DCMD) neurone, and of some smaller visual interneurones (S‐units), were recorded in the ventral nerve cord of adultSchistocerca gregariaForsk., in response to a stationary disc (25o) or a small spot (0.2o) stimulus. The discharge rate of each neurone was plotted over a period of 5 s exposure; the total number of spikes in this period was also noted. The DCMD response to the 25odisc was a high‐frequency burst falling off quickly to a low rate; the 0.2ospot evoked a prolonged discharge with an early peak in rate. In S‐units the discharge was prolonged with both targets; the rate rose to an early peak in each case, with a much higher rate for the larger disc. For the DCMD the total number of spikes per stimulus (5 s) was greater for the 0.2ospot; for S‐units it was greater for the 25odisc. Thus an increase of about 30‐fold in the number of ommatidia stimulated resulted in a fall in the total DCMD response to about one‐quarter; a similar increase evoked a rise of about 6‐fold in the S‐unit response. When the 25odisc was presented at progressively reduced intensities the total spike response of the DCMD rose steadily to a maximum at about 2.9μW m‐2; using the same procedure the spike output of S‐units, initially high, declined monotonically. The role of inhibition in these

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00918.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.The movements and orientation of adultGerris remigisSay (Hemiptera; Gerridae) were examined in an artificial stream to determine the mechanisms by which these stream‐dwelling waterstriders compensate for and/or avoid downstream drift, and to compare the movement tendency of pre‐ and post‐diapause adults.G. remigisrespond to current by turning to face directly into the current (rotational orientation), intermittently rowing against the current (translational orientation), and moving onto land to avoid the current. These rotational and translational responses enableG. remigisto maintain their positions in currents =S10 cm s‐1. However, avoidance increases with current speed, and few animals are found where currents exceed 10 cm s‐1. These observations correlate well with the observed distribution of adultG. remigisin a natural stream.Comparisons between life stages reveal that post‐diapause adults move more, and are more susceptible to drift than pre‐diapause adults. Post‐diapause adults also avoid even slight currents (<5 cm s_1) by seeking land, while pre‐diapause adults do not show a significant preference for land until currents exceed 10 cm s‐1. These data suggest that previously reported differences in the movement tendency of pre‐ and post‐diapause adults in the field may reflect physiologically‐based behavioural differences between these two life stages rather than merely direct respon

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00919.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.. A marked seasonal variation in the hair colour ofCtenucha virginica(Esp.) larvae is observed under field conditions. During the autumn and spring larvae are black and yellow, while during the summer they are predominantly yellow. Under sunny conditions in the field, or when exposed to a radiation heat source in the laboratory, black and yellow larvae have significantly higher body temperatures than yellow ones. As larvae feed over a limited range of temperatures, it is proposed that seasonal changes in hair colour may help larvae to thermoregulate, thereby maintaining body temperatures within the range where feeding is possible.

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00920.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.. Azadirachtin in blood fed to adult femaleAedes aegyptithrough an artificial membrane does not cause feeding inhibition over a wide dose range (0–200 ng/female), and high doses of ingested azadirachtin fail to inhibit or delay oviposition. However, significant, transient retardation of oocyte growth is observed for up to 72 h after feeding. Immature oocytes are observed in 86% of azadirachtin‐fed females decapitated 10 h after a blood meal, whereas 96% of decapitated control females contain maturing oocytes. This suggests that azadirachtin delays the release of one or more factors from the head that regulate oogenesis. We propose that adult females overcome the effect of azadirachtin by rapid metabolism rather than by excretion of the compound, since by 2 h after a blood meal, only 0.1% of ingested azadirachtin was recovered from excreta and 5% recovered from the b

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.. The females of the tropical BruchidBruchidius atrolineatus(Pic) (Coleoptera) produce a sex pheromone that influences male behaviour. This pheromone, tested on males in an olfactometer, triggers characteristic antennal movements followed by a distinct chemo‐anemotaxis. Sex pheromone production depends on the age of the females and is partly correlated with their ovarian activity. Females 0–24 h old are not attractive, but they begin to attract males on the second day of adult life. Vitellogenesis seems to correlate with the emission or the production of the pheromone but there is no precise synchrony between the two phenomena which are probably induced by the same endocrine factors. Within 1 h after mating there is a decrease in the females' attractiveness, which lasts at least 48 h. Under our experimental conditions no particular rhythm of production or emission of the sex pheromone inB. atrolineatuscould be obser

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.. Mating receptivity in females of the ladybird,Harmonia axyridisPallas (Coleoptera: Coccinellidae), was studied with reference to internal and environmental conditions. Females sometimes reject copulation: they run away, or shake off the male and bend the abdomen upwards. Newly emerged females show a greater likelihood of accepting copulation with an advance in the stage of ovarian development, this being related to age. Females usually mate repeatedly, but frequently show refusal behaviour under unfavourable food conditions. Dissections reveal that females which accept copulation have a greater number of mature eggs in the ovary than do rejectors. Results also suggest that the food conditions are a major environmental factor, directly controlling mating receptivity.

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00923.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT.. There is a direct quantitative relationship between the free‐running period (r) of the circadian stridulation rhythm of male Australian field crickets,Teleogryllus commodus(Walker), and the intensity of the constant light conditions. BothT. commodusand the house cricket,Acheta domesticus(L.), show free‐running periods of the singing rhythm ofc.24 h when the light intensity is 0.00025 lux. In both species the severance of the three ocellar nerves significantly slows the circadian period which is indicative of a reduced perception of the available light intensity. To test whether this period reduction is a peripheral or a central effect, electro‐retinograms (ERGs) were recorded from compound eyes of maleT. commoduswith the ocelli fully functional, then occluded, and then uncovered. The size of the compound eye ERG is reduced by 20% with ocellar occlusion and can subsequently be fully restored to the intact level, which indicates that the ocellar effect is a peripheral one. Intensified CoCl2fills reveal one neurone inA. domesticusand two inT. commoduswhich travel from the lateral ocellar nerve out into the ipsilateral optic lobe of the compound eye. These neurones all terminate in or distal to the lobular neuropile. The data are interpreted to indicate a role for ocelli in modulating the light intensity perception of the compound eye. The final effect of the ocellar afferents is at a peripheral level prior to the input of the visual information to the optic lobe circadian pacemaker. Hence ocelli play an indirect role in circadian rhythmicity, augmenting the sensitivity of the primary photoreceptors to better perceive photic entrainment si

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1988.tb00924.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY