摘要:

Abstract.Flight fuel relations of crowded and isolatedLocusta migratoria migratorioideswere investigated in younger (12–16 days after fledging) and older (27–30 or 27–32 days after fledging) adult males.No phase polymorphism dependent differences were found in resting haemolymph carbohydrate levels of the younger locusts.In the older age group, resting haemolymph carbohydrate levels were slightly though significantly higher in the isolated than in the crowded locusts.Injection of various doses of synthetic adipokinetic hormones (AKHs) did not induce marked changes in haemolymph carbohydrate levels and no differences were found between crowded and isolated locusts.A 30 min flight led to the same decrease in haemolymph carbohydrate levels of isolated and crowded locusts, 43.3% and 44.6% of the resting levels, respectively.We concluded, therefore, that the results do not seem to indicate that isolated locusts rely more heavily on carbohydrates as flight fuel than crowded locusts.Hyperlipaemic responses to flight were less intense in isolated than in crowded locusts, but phase polymorphism dependent differences in flight‐induced increase of haemolymph lipid levels were not parallel in 12–16‐day‐old and 27–32‐day‐old males.In the younger age group the difference was mainly in the duration of flight needed to induce full response which appeared already after 20 min of flight in the crowded locusts, but only after 45 or 60 min of flight in the isolated ones.In contrast, the older isolated locusts showed markedly lower haemolymph lipid elevations than the crowded locusts even after 30, 45 or 60 min of flight.The hypothesis is forwarded that isolated locusts have a rather coarse adipokinetic strategy focused on a single long‐distance migratory flight, whereas gregarious locusts possess a fine adipokinetic balance for reiterative migratory flights and saving fuel reserves for unpredictable lon

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.When alarmed, caterpillars of the tortricidEpinotia abbreviana(Fabricius) and the yponomeutidYponomeuta padella(Linnaeus) parachute at the end of a single life‐line spun out by the head spinnerets.Two methods are employed to climb back up the line.The first makes use of alternate movements of the left and right set of thoracic legs, aided by side‐to‐side movements of the body.This results in the life‐line being wound in around the third pair of thoracic legs.The second method is based on the normal peristaltic rhythm used when walking on a solid substrate.Dorsoventral curling movements gradually transfer life‐line from the thorax along the succession of abdominal pro‐legs to the claspers at the end of the body.The life‐line has similar physical characteristics to spider orb‐web silk, and a breaking force equivalent to 5–8 times body weight.The holding force of the claspers when in contact with the ground exceeds the breaking force of the life‐line.These studies demonstrate the flexibility of caterpillar locomotion, when confronted wit

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00829.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.1‐octen‐3‐ol, a component of the body odour of ruminants, is demonstrated to be an attractant for host‐seeking, parous femaleCulicoides impunctatusGoetghebuer (Diptera, Ceratopogonidae).This compound was electrophysiologically and behaviourally active and, in the field, released at 0.11 ± 0.01 mg/day, increased femaleC.impunctatuscatches over a seven‐day period compared with control catches.When 1‐octen‐3‐ol was combined either with live female midges or an extract of female midges in an electroantennogram assay, additive effects were recorded.Behaviourally, the same combination resulted in both enhanced attraction and repellency, depending on concentration.Attraction was recorded mainly when sub‐threshold concentrations of the separate components were combined.The potential of such a combination as an effective field

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00830.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.In the field over short grass, pheromone‐stimulated oriental fruit moth males,Grapholita molesta(Busck), flying under high windspeeds tended to steer courses more into the wind and to increase their airspeeds compared with those flying in low windspeeds.Thus, optomotor anemotaxis enabled the males to steer relatively consistent upwind track angles and to maintain an upwind progress of betweenc.50–100 cm/s despite variable wind velocities.Zigzagging flight tracks were observed at both 10 m and 3 m from the source, as were tracks with no apparent zigzags.Transitions from casting to upwind flight or vice‐versa were observed.The durations of the intervals between reversals during both upwind zigzagging flight and casting were consistent with those observed in previous wind‐tunnel experiments.The control of altitude was more precise during upwind zigzagging flight than during casting.In general, the side‐to‐side deviations in the tracks were greater than the up‐and‐down deviations, with both the side‐to‐side and vertical distances and their ratios being consistent with previous wind‐tunnel studies of pheromone‐mediated flight.One difference between the field and laboratory flight tracks was that males in the field exhibited much higher airspeeds than in the wind tunnel.Males occasionally were observed to progress downwind faster than the wind itself, and further analysis showed that they were steering a downwind course in pheromone‐free air following exposure to pheromone, which is the first time this has been recorded in moths.We propose that such downwind flight may aid in the relocation of a pheromone plume that has been lost due to a wind‐shift, by enabling the moth to catch up to the pheromone as it recedes straight do

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00831.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.The aim of this study was to characterize the vibratory signals produced by the parasitoidSympiesis sericeicornisNees (Hymenoptera: Eulophidae) while foraging on apple leaves infested by one of its hosts, the spotted tentiform leafminerPhyllonorycter malella(Ger.) (Lepidoptera: Gracillariidae).This leafminer changes its behaviour as a function of the parasitoid's behaviour to escape parasitization.We propose that the leafminer uses vibrations triggered by the parasitoid to detect the presence of its enemy.We measured vibrations produced by a foraging parasitoid on a mine with a laser vibrometer.By recording concurrently the behaviour of the parasitoid on video, vibrations could be assigned to particular behaviours.Subsequently, vibrations were characterized by their dominant frequencies and intensities.The behaviours Landing andTake‐offboth produced strong impact‐like vibrations characterized by an initial irregular phase during which frequencies up to 25 kHz occurred followed by a slow decaying regular phase.Vibrations elicited byMoving, StandingandProbingshowed no clear temporal pattern.DuringProbing, dominant frequencies of up to 5.6 kHz were observed frequently at intensities well above the background noise (>10 dB).DuringMovingandStanding, vibrations were more scarce and of lower frequencies and intensities.Due to their impact‐like nature, vibrations produced byLandingandTake‐offare probably not specific to the parasitoid.Vibrations produced byMovingandStandingare difficult to detect and not reliable because of their non‐specificity.Therefore, onlyProbingprovides a reliable and detectable source of information for the host.The vibrations elicited duringProbingcould account for the evasive behaviour that is observed in this and other l

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00832.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Supercooling points and chill tolerance were compared among nymphs and adults of the ixodid ticksDermacentor variabilis, Amblyomma americanumandIxodes scapularis(Acari: Ixodidae).Supercooling points in the range of<‐22 to ‐18°C were observed for nymphs, and ‐22 to ‐8°C for adults.The lower lethal temperatures observed under dry conditions, ‐14 to ‐10°C, were warmer than the supercooling points, but still much colder than ‐4.8°C, the lowest temperature recorded from a likely tick habitat in southwestern Ohio.Based on our experiments, spontaneous freezing and direct chilling injury are not significant mortality factors in these species in the field.Mortality was observed between ‐5 and ‐3°C forA.americanumandD.variabilisnymphs chilled for 2 h while in direct contact with ice.This mortality is probably due to inoculative freezing.Given the requirement for a rather humid microhabitat for off‐host survival, these findings suggest that inoculative freezing is an important cause of overwintering mortality in these med

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00833.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Adults of the dung flyNeomyia cornicina(Fabricius) were fed continuously on either dung containing no ivermectin (control dung) or dung containing 0.125 μg g‐1or 0.25 μ g‐1ivermectin (wet weight).Comparisons were made between the behaviour of flies during the first 24 h of dung feeding and that observed after 96 h of feeding.Subsequent experiments investigated the effects of ivermectin ingestion on three measures of locomotory ability: escape time, time to re‐right, and capture time.Analysis of behavioural data showed a significant reduction in the activity of ivermectin‐fed flies compared to that of the controls.After 96 h of feeding on dung containing ivermectin, there was a significant increase in the duration of time spent standing and a reduction in duration and frequency of walking and grooming behaviours compared to controls.Seventy‐two hours after the onset of dung feeding, flies fed dung containing ivermectin took significantly longer to escape from a glass tube and to re‐right themselves after overturning than flies fed control dung.The time taken to capture flies that had fed on dung containing ivermectin at 0.25 μg g‐1was significantly shorter than that required to catch control flies when flies from the different treatment groups were presented bl

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00834.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.In southern parts of the United States the cabbage looper moth,Trichoplusia ni(Hübner) (Lepidoptera: Noctuidae), is multivoltine, and therefore successive generations experience different environmental conditions during development from larvae to adults.Since environmental conditions are thought to influence pheromone communication, we tested the effects of two different temperature and light regimes (selected to mimic those occurring in the spring and summer growing seasons in the south) during rearing on the response characteristics of the adult male olfactory receptor neurons responsible for detecting the major component of the female pheromone.The dose‐response functions of receptor neurons from the warm‐ and cold‐reared insects were similar in both their slopes and thresholds to stimulation with the major component of the female‐emitted pheromone, (Z)‐7, dodecen‐1‐ol acetate and (Z)‐7, dodecen‐1‐ol, a behavioural inhibitor.In double pulse experiments, designed to emulate the temporal dispersion of pheromone in nature, neurons were stimulated with short pulses (200 ms) of (Z)‐7, dodecen‐1‐ol acetate separated by varying intervals.Intervals as short as 30 ms reduced the response to a second pulse by over 50%.When the intervals between pulses were longer than 2 s, significant differences were not seen between the responses to the first and to the second pulse.These temporal response patterns were similar in both war

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.The effects of food quality on growth and body composition of the collembolanOrchesella cincta(L.) (Entomobryidae) were investigated to determine optimal values for dietary nitrogen.Hyphae ofCladosporium cladosporioidescontaining 2.2%, 2.7%, 4.0% and 6.2% nitrogen were used as food sources.These different nitrogen contents were obtained by adjusting the medium on which the fungi were grown.Collembola were fed on one of these four food sources for 8 weeks.O.cincta grew faster and reached a higher asymptotic body mass when fed on fungi with 4% or 6.2% nitrogen content: this effect decreased with higher nitrogen content.The lipid concentration in the animals was negatively correlated with dietary nitrogen content, whereas protein concentration was positively correlated.Glycogen concentration was not found to correlate with the composition of the food.A mechanism is proposed by whichO.cincta compensates for low dietary nitrogen by consuming more to maintain a relatively constant amount of protein in its body and, as a result, accumulates more fat than animals fed on fungi with a higher nitrogen content.

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Third‐instar larvae of the goldenrod gall fly (Eurosta solidaginisFitch) live inside ball galls on goldenrod plants from summer to the following spring.Because galls are highly exposed to the weather, larvae experience substantial variations in body temperature.This study documents the oxygen consumption of gall fly larvae with regard to the effects of ambient temperature, seasonal conditioning, and prior exposure to subzero temperature.The body mass of larvae doubles between the late summer and the autumn; it subsequently undergoes a modest decline by early winter.The O2, consumption of field‐acclimatized larvae increases with ambient temperature, especially between 0 and 10°C (Q10= 2.6‐3.4).The thermal sensitivity of metabolism declines at higher ambient temperatures, most notably during the autumn/early winter.After exposure to 15°C for 1 week, autumn and early winter larvae maintain much lower rates of O2consumption than do late summer specimens.Prior exposure to ‐5°C for 24 h did not influence the O2consumption of larvae.Low thermal sensitivity of O2consumption, especially at higher ambient temperatures, is an energy‐sparing mechanism during seasonal inactivity.Indeed, the persistence of this metabolic pattern in larvae exposed to 15°C suggests that they have entered a stat

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1996.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY