摘要:

ABSTRACT.Orchestia cavimanaHeller (Amphipoda, Talitridae) were shown to orient to the geomagnetic field as well as to an anisotropic light field. When tested in an isotropic light field the orientation in the geomagnetic field was either in or opposite to the compass direction of the light vector of the anisotropic light field in which the animals had lived before the test, and this orientation was upset predictably by changing the magnetic field with Helmholtz coils. The polarity of the reaction in both magnetic orientation and photo‐orientation was correlated with pre‐experimental water loss. The magnetic orientation ofO. cavimanais compared with that ofTenebrio molitor, and its biological significance discus

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00648.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.Supernumerary larval instars were produced whenGalleria mellonellaL. (Lepidoptera) larvae were chilled at 0°C. Although sensitivity to cooling stress of the last instar and younger larvae were generally the same, only penultimate and the last instar larvae showed a significant correlation between their age and the number of additional larval moults. Chilling stress induced a rapid and persistent increase in the JH titre of the last instar larvae. Severing the ventral nerve cord resulted in a predictable loss of the ability to produce supernumerary moults in chilled last instar larvae. The data suggest that sensory input stimulates allatotropic hormone secretion by the brain of chilled larvae. The possible mechanism controlling supernumerary moulting is discussed

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00649.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.The incidence of diapause inEphestia kuehniellaZeller from an unhealed granary in Scotland was influenced by both photoperiod and temperature. At 25°C, nearly 50% of larvae entered diapause when reared in continuous darkness (DD) and up to 30% did so in short photoperiods. Little diapause was detected around LD 14:10 but a second, smaller peak of about 20% occurred at LD 16:8 and LD 18:6, falling away again to nearly zero in continuous light. More larvae entered diapause when reared continuously at 15 or 20°C than at 25 and 30°C. However, when larvae reared from hatch at 25°C in LD 16:8 were transferred after 1 week to 15°C in LD 9:15, almost twice as many entered diapause as did those reared at 15°C throughout. The sensitive phase for diapause induction occurred near the start of the final instar. The mean duration of diapause was between 2 and 3 months in most photoperiods at 20 and 25°C, and was shorter at 15°C. However, in DD at 25°C, it lasted about 7 months. Termination of diapause was hastened in larvae reared at 25°C in DD by transferring them to LD 14:10, and also by chilling them at 7.5°C for 6 weeks before returning to 25°C in DD. In an unhealed store in southern England, viable adults emerged from May to July and originated from larvae which terminated diapause relatively late. It would appear from the results of transferring larvae back to the laboratory at various times during the winter that some phases of diapause development were completed quite early after exposure to low temperatures, although no further development took place in the store until temperatures rose aga

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00650.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.In post‐embryonic development, the visual system of the cricketNemobius sylvestris(Bosc) shows a regular increase in the length and number of the ommatidia and a decrease of inter‐ommatidial angle so that the adult's is a third of the value in the first larval instar. Further, a 20° widening of the binocular visual field, in the horizontal plane at least, and a three‐fold increase of the inter‐ocular distance improve the potential for binocular vision. Behavioural experiments showed that the insect orientates with differing precision depending on the distances to targets of constant angular size. Further, in a choice situation between two such vertical targets, the cricket orientates most strongly towards the closer of the two, even at target distances of 52 and 130 cm from its point of decision. In fixed tethered animals, discrimination between a close and a distant target is still possible, but disappears when the head is waxed to the thorax, so that any relative movement between the animal and the object is prevented. As these capabilities exceed the possibilities of binocular triangulation, the possible role of other mechanisms is discussed, particularly that involving movement parallax using b

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00651.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.When offered the choice between a germinating tick bean (summer host) and a detached spindle leaf (winter host) adult gynoparae ofAphis fabaeScop. showed a distinct preference for spindle, as judged by site of larviposition. However, when offered the same alternatives, all four larval instars showed a settling preference for bean. A switch in host preference therefore occurs at or shortly after final (fourth) moult. Fifth instar, supernumerary larvae induced by juvenile hormone (JH I) treatment also preferred bean, indicating that the host preference switch at the fourth moult had been inhibited. Larval/adult intermediate forms produced by JH I treatment, but which were capable of parturition, showed a significant increase in the acceptability of bean as a larviposition site. Acceptability was proportional to the degree of juvenilization. Thus, although larviposition is an adult prerogative, JH I can influence the preferred site. This may, however, be an indirect effect which reflects a juvenilized settling preference.

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00652.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.Ecdysteroid and cyclic nucleotide titres were determined in ovaries, fat body, muscles, haemolymph and the remaining carcass tissue (cyclic nucleotides only in ovaries and fat body) of females of the Mediterranean field cricket,Gryllus bimaculatusde Geer, during its adult life span. Under a daily temperature cycle 24°: 12°C (16:8h), ecdysteroid levels of the ovaries and fat body reached maximal values 5 times as great and about 10 days earlier than they did under constant 20°C. Under both temperature regimes the highest ecdysone concentrations coincided with the maximum in ovarian fresh weight as well as with the maximum oviposition rate. In the ovaries, titres of c‐AMP and c‐GMP changed roughly in parallel, the levels of c‐GMP, however, were much lower than those of c‐AMP. A comparison of the cyclic nucleotide profiles in the ovaries with the ecdysteroid profile shows that the cyclic nucleotide concentrations increase when ecdysteroid titres are still low, and that the highest cyclic nucleotide levels were reached 6–12 days earlier than the highest ecdyst

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00653.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.LarvalTrichoplusia ni(Hübner) (Noctuidae) parasitized byChelonussp. (nearcurvimaculatus) (Braconidae) precociously initiated pupation during the penultimate fourth instar. The temporal sequence of developmental markers exhibited by parasitizedT. niclosely matched the temporal sequence in normal, pupating larvae. The parasitized larvae did not complete pupation, but consistently stopped development at a stage recognizable by a certain set of markers. This halt was observed in hosts from which parasites emerged and from hosts which had been stung but from which no parasites emerged. Weight gain and food consumption by parasitized hosts were significantly lower than normal, although most reached the fourth instar at the same time as normal larvae. Measurement of head capsule widths indicated that the width in precociously pupating larvae was less than the critical width associated with attainment of the pupation instar of normal larvae

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00654.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.On passing from clean air into a homogeneous cloud of sex pheromone in a wind tunnel flying maleAdoxophyes orana(F.v.R.) (Lepidoptera: Tortricidae) turned more or less upwind and reduced the time and distance between their switchings of track from one side of the wind line to the other. These responses became adapted under the constant pheromone stimulation in the cloud, thereby arresting upwind progress; but the adapted moths would now ‘lock‐on’ to an added pheromone plume and advance upwind along it. Moths also locked‐on to the border of a pheromone cloud, not by turning back on losing the scent as previously supposed but by initiating the above programme of small‐amplitude, crosswind movements (reversing anemomenotaxis). The onset and cessation of the pheromone stimulus produced anemotactic responses that differed quantitatively within a continuum, not two distinct kinds of response as previously supposed. The behavioural mechanism whereby uniform permeation of an area with synthetic sex pheromone can prevent males from finding females is rec

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00655.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.The cicadelloid leaf‐hoppers,Eurymela distincta(Signoret) andEurymela fenestrata(Le Pelletier&Serville), feed on the phloem sap ofEucalyptusspp. The osmotic pressure profile of haemolymph and gut fluids is consistent with a filtration mechanism based on passive osmosis. This is responsible for shunting water rapidly from foregut to hindgut in the relatively simple filter chamber. The osmotic gradient which drives the system is probably produced by active secretion of sodium and potassium into the Malpighian tubules and posterior midgut. Although the osmotic pressures in all parts of the system are higher, the mechanism is probably similar to that previously described for xylem‐feeding cicadas.The major haemolymph cations are sodium and magnesium and the concentrations of sodium and magnesium in the urine are higher than potassium. A variety of storage granules in the midgut contain calcium, phosphorus (as phosphate), ferric iron, zinc, magnesium, manganese and cop

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00656.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.A pre‐exposure regime was developed to test the hypothesis that arrestment of in‐flight behaviour in Oriental fruit moths,Grapholitha molesta(Busck), to high dosage and/or high %(E)‐8‐dodecenyl acetate blends was due to a high proportion of E8‐12: Ac in the pheromone blend. When tested in a sustained‐flight tunnel to various ratios of (Z)‐ and (E)‐8‐dodecenyl acetate plus a constant % of Z8‐12: OH at two dosages (3 and 100μg), males displayed an optimum number of completed flights to the source to the natural 6%Eblend at 3 μg, with significant decreases in response levels occurring to high %Eblends at both dosages. Pre‐exposure of males to E8‐12: Ac alone enhanced their response at each dosage to selected higher %Eblends that normally elicited low numbers of completed flights. Pre‐exposure enhanced all aspects of the flight response, but this was dependent on both dosage and duration of pre‐exposure, with later behaviours in the sequence (landing and hairpencil display) requiring greater amounts of pre‐exposure than early behaviour (taking flight). Pre‐exposure did not affect high response levels to optimal blends or low response levels to the highest or lowest blends tested at each dosage. The selective nature of the pre‐exposure effect implied alteration of central processes in discrimination of blend rather than disturb

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1981.tb00657.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY