摘要:

SUMMARYThe spectral energy distribution of the light reflected from various leaves and soils has been measured and corrected for ‘standard’ sunlit conditions, and then compared on the basis of Moericke's evidence that aphids of many species distinguish two parts of the spectrum as colours, alighting and probing in response to wavelengths greater than 500μ.Alightments byBrevicoryne brassicaeandMyzus persicaein the field occurred preferentially on leaves reflecting a greater proportion of long‐wave energy, with little or no regard for the ‘botanical’ (plant‐taxonomic) host status of the plants for each aphid. The colour attraction of such ‘yellow‐sensitive’ aphids serves rather to bias their alightments towards plants of the appropriate physiological type.Laboratory experiments confirmed the existence, inferred from field observations, of a second, non‐specific mechanism of visual attraction normally involved in alightments on plants, namely a close‐range optomotor reaction with both orienting and arresting components.The light reflected from various soils embodied maximum energy at the extreme long‐wave end of the spectral range affecting aphids, while the leaf energy peak was 540–560 mμ. The predominantly long‐wave emission from both leaves and soils contrasts sharply with the light from clear or clouded skies, wherein the peak energy region lies below 500 mμ. The aphids' type of colour vision thus provides for a primary discrimination between sky and ground, beside any subsidiary discriminations among plants and soils.Low‐flyingAphis fabaewere attracted to white surfaces as well as to yellowing leaves in the field. The change in the migrant's behaviour from ‘distance flight’ in the upper air to low‐level ‘alighting flight’ appears to be due, not to a reversal of the response to short‐wave sky light from positive to negative, but simply to a relative strengthening of the positive

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03587.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The relation between body weight and resistance to γ‐BHC and diazinon was studied in experiments using the desert locust (Schistocerca gregaria) and the African migratory locust (Locusta migratoria migratorioides).In all experiments withSchistocerca, resistance was proportional to weight within any one age and sex group. Resistance to diazinon (per unit body weight) decreased with age, that of the males at a faster rate than that of the females. Against γ‐BHC the insects showed a nearly twofold increase in resistance about 1 week after fledging.Within groups ofLocustathe resistance to diazinon was found to be independent of weight, but the resistance to γ‐BHC was dependent on weight. Similarly the resistance to diazinon at different ages after fledging was independent of age but resistance to γ‐BHC increas

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03588.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The effects of a change in temperature (15–28° C.) on the toxicity of dilute suspensions of DDT to larvae ofAédes aegyptiL., as assessed by a photomigration method, depended on the stage of the test during which the temperature was changed. Increase in temperature during exposure to DDT (0.02 p.p.m. for about 1 hr.) increased the toxic action. When larvae were left in the suspensions for the duration of the test (3 hr.‐4 days), increase in temperature throughout the test decreased the toxic action of a very low concentration of DDT (0.002 p.p.m.), but had no effect with higher concentrations (0.1–0.2 p.p.m.). Toxic action was greater in larvae held at a low temperature than in larvae held at a high temperature after treatment (0.025 p.p.m. for 3 hr.). Such toxic action was reversible: a change from high to low temperature increased paralysis, and larvae, paralysed at a low temperature, recovered when the temperature was

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03589.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

SUMMARYThe toxicity of DDT to insects usually increases as the post‐treatment temperature is decreased in the commonly used temperature range (30‐10° C.). The toxicity increased further when the post‐treatment temperature of adultTenebrio molitorL., dosed by topical application, was decreased from 10 to 6° C. However, when the post‐treatment temperature was decreased still more (down to — 1° C.), the toxicity by topical application or by injection apparently decreased again. The size of this ‘positive temperature coefficient’ below 6° C. decreased as time passed after treatment. Differences in toxicity below 6° C. were more apparent than real, and were the result of differences in the speeds at which symptoms appeared.The slight toxic action at very low temperatures was evidently not caused by failure of DDT to penetrate the cuticle, or to reach its site of action. More probably, the speed of the chemical or physical process which actually caused paralysis was extremely low at the ver

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03590.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

SUMMARYThe relationships between increased oxygen uptake and locomotor ataxy or death induced by LD50's ofn‐valone (2‐n‐valeryl‐1,3‐indandione), γ‐BHC,p,p'‐DDT, dieldrin, DNBP (2,4‐dinitro‐6‐sec.‐butylphenol), malathion and allethrin, in individual lesser mealworm beetles (Alphitobius laevigatusF.) have been investigated.n‐Valone did not increase the rate of oxygen uptake of treated beetles. After dosage with DDT or malathion, increased oxygen uptake occurred only in beetles which were knocked down and beetles knocked down always died. After dieldrin treatment, increased oxygen uptake was always associated with knock‐down, but a few knockeddown beetles recovered. γ‐BHC, allethrin or DNBP caused knock‐down or serious locomotor ataxy and increased oxygen uptake in all the treated beetles, but those which eventually died reached higher peaks in rate of oxygen uptake. The similarities and differences between the effects of the various insecticides are discussed together with some aspects o

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03591.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

SUMMARYThe pollinators of red clover are described and the relationship between the number of seeds set per head and the yield of clover seed is recorded.Two methods of recording insect pollination in relation to the numbers of seed set per head of clover were explored in 1955. In 1956 and 1957 recording of actual crops of seed was continued.Certain species of humble‐bees are important in the production of singlecut red clover seed, and in the production of doublecut red clover seed in 1956, although another factor, possibly honey‐bees, was dominant in 1957.There was no indication that ‘robbing’ was associated with a lower ‘seed set’; on the contrary in 1957 it was associated with a higher ‘set’, possibly because it attracted honey‐bees to the crop.The data showed that the numbers of the different species of humble‐bees varied, but gave no indication of the relative effectiveness of the various species in pollination. Those present in greatest numbers were of most value for pollinating red clover.Pests and diseases likely to reduce seed set were found to be negligible during 1955, 1956 and 1957. Differences in fertility between one field and

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03592.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

SUMMARYUsing a standard 9 in. diameter disc‐dropping suction trap, the aerial density ofAnisopus fenestralisabove bacteria beds was assessed hourly on 410 24‐hourly occasions over a period of 19 months, and the prevailing temperatures and wind velocities were recorded. Between o and 10 m.p.h. wind velocity there was a gradual rise in catch associated with a rise in temperature to an optimum, beyond which the catch decreased. This optimum fell as wind velocities rose; it occurred between 70° and 75° F. at winds between 2 and 4 m.p.h., at 65–70° F. with winds between 4 and 6 m.p.h. and at 60–65° F. between 6 and 8 m.p.h. At all temperatures between 30 and 80° F. the catch fell as wind velocity increased from o to 10 m.p.h. By comparing the dusk catches on successive days a significant positive correlation was found between the deviation in log catch from a 3‐day running mean and the corresponding temperature deviation, except when the wind velocity deviation exceeded + 2. There was also a significant negative correlation between deviation in log catch from the running mean and the corresponding deviation in wind velocity, except when the temperature deviation exceeded — 2.The average regressions showed that for each °F. rise in temperature the log catch was raised by 0.14 and for each 1 m.p.h. rise in wind velocity the log catch was decreased by 0.19. Expressed arithmetically the catch was doubled by a 2.2° F. rise in temperature or by a fall in wind velocity of approximately 1.5 m.p.h.The aerial density was affected not only by weather but also by fluctuations in theA. fenestralispopulation within the bed arising from direct and indirect climatic effects on its food supply—the microbial growths within the bed. Lower winter temperatures favour an accumulation of food, so the patterns of seasonal incidence of the flies from year to year are affected by the severity of

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03593.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

SUMMARYLaboratory experiments and field trials in town and country were carried out with four reputedly narcotic substances (pentobarbital sodium, dithiobiuret, tri‐orthocresyl phosphate and chloralose) and four poisons (picrotoxin, nicotine, parathion and sodium fluoroacetate) to investigate their value in the control of pigeons, corvids and sparrows.The alpha isomer of chloralose was the most satisfactory material tested; it normally produces narcosis from 15 to 30 min. after ingestion on wheat or maize and this lasts from 10 to 20 hr. Its potency was assessed using treated grain, gelatine capsules and flour pills, administered with and without food, and also from field data. It was most effective on grain and least effective in gelatine capsules. The flour pill method was the most satisfactory for obtaining an LD 50 figure which for alpha‐chloralose used against feral pigeons was about 131 mg./kg. live weight. The pure beta isomer of chloralose was ineffective.Using alpha‐chloralose, urban populations of feral pigeons were reduced from 48 to 83% in three to seven treatments. In fifty‐two trials in towns 1544 feral pigeons were disabled, only five of the 1409 picked up being found at a greater distance than 500 yards from the baiting point. With five different concentrations between 2.5 and 0.5% by weight in bait, the lower concentrations produced lower mortality without affecting the size of the catch. Bait containing chloralose at 1.5% by weight gave the greatest efficiency with a mortality of less than 50% and this concentration is recommended for practical control operations.In towns the risk of accidentally affecting legally protected species is negligible, whereas in rural districts it is much higher, at any rate when grain baits are used. The use of maize greatly reduces the risk to small birds which cannot swallow the large grains.Four series of field trials in Kent and East Anglia in autumn and winter caught only seven wood‐pigeons and one stock‐dove during a total of 72 baiting days. This disregard for cereals is discussed and is thought to be due to changing ‘feeding images’.In four field trials to catch corvids, using alpha‐chloralose on maize, only fourteen were narcotized. Two field trials using alpha‐chloralose against house‐sparrows were unsuccessful, but eighty house‐sparrows were captured incidentally during four of the trials on feral pigeons. With the possible exception of nicotine none of the other substances tested showed promise for controlling birds. The use of blue‐coloured baits, as a warning to the public, reduced takes by feral pigeons but did not prevent feeding altogether.The value of alpha‐chloralose as a control agent and the hazards it presents to wildlife are discussed; its use probably offers a better means of controlling feral pigeons in tow

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03594.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

SUMMARYThe eradicative and protective activities of the salicyl‐, 3‐chlorosalicyl‐, 5‐chlorosalicyl‐ and 3,5‐dichlorosalicyl‐anilides and‐para‐chloroanilides, against cucumber powdery mildew (Erysiphe cichoracearumDC.) and tomato leaf‐mould (Cladosporium fulvumCke.) have been determined byin vivoglasshouse tests on pot plants. No compound was more effective than salicylanilide against either disease at a non‐phytotoxic concentration.In addition, thein vitrofungitoxic activities of these compounds against spores of tomato leaf‐mould have been determined; several were considerably more act

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03595.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

SUMMARYExperiments were made in 1957‐59 on the fungicidal control of club root in cauliflowers (summer and winter), brussels sprouts, summer cabbages and savoys. Plants were treated immediately before setting out or in their final position.Pure (100%) calomel used in suspension at 1 and 2 oz. per pint gave best control of the disease: the 4% calomel paste method was effective but treated plants suffered an initial check from which they only slowly recovered. Formulations of pentachloro‐nitrobenzene and of aldrin did not give satisfactory control.Several methods of applying metham‐sodium were tried but gave poor control of the di

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1961.tb03596.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY