摘要:

With each of nine DDT analogues, two types of simple aqueous suspension were made, one containing crystals of uniform size, and the other containing colloidal particles. The toxicities of each pair of suspensions were compared by a dipping method on adultOryzaephilus surinamensisL., kept at n° C. for 24 hr. after treatment. The colloid was always as toxic as the crystals, or more toxic. This difference in toxicity varied from one analogue to another. It was related to the physical properties of the analogue in the following way.Dipping applies poison to the insects; the amounts retained could usually be found by extraction and microanalysis. Retention of poison from colloidal suspension was about the same for each analogue; but crystals were retained either more or less efficiently than colloid, depending on their size and shape. Poorest retention was found with plate‐like crystals of about 25μ.The true ratio of toxicities for each analogue (colloid : crystals) was found by correcting the observed ratio for differences in retention; but even then there were still big differences amongst the ratios given by the different analogues.The true ratio was taken as a measure of the difference in speed of action between the two forms of poison. If the compound could kill O. surinamensis by fumigant action alone, the true ratio was very small. Otherwise, it seemed to depend on two physical properties related to the process of solution of poison in the wax of the insect cuticle. They were both measured in in vitro tests. The film made by evaporating a drop of colloidal suspension on glass is at first globular, but it may sooner or later crystallize. The film made by evaporating a drop of a suspension of crystals can be dissolved in olive oil. If the film of crystals brought about saturation of olive oil slowly and if, in addition, the deposit from colloid crystallized slowly, the true ratio was large. Unless the analogue had both of these properties, the true ratio was small. If the analogue had one or other of the properties, the true ratio could be increased either by increasing the crystal size or by decreasing the rate of crystallization.Physical properties of this sort may often affect the results of tests of insecticides, and should be taken into account when the toxicities of different compounds are compared.There seems to be no relation between lipoid‐solubility and toxicity of compounds in the DDT group. Rate of solution is probably more impo

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02466.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The fate of diethyl 5‐2‐(ethylthioethyl) phosphorothiolate (demeton‐S) in white mustard(Brassica alba), borage(Borago officinalis)and field beans(Viciafaba)has been followed over several weeks using the radioactive tracer technique. Radio‐assay of nectar samples from flowers which opened a few days after spraying showed that no unchanged demeton‐S, but that small amounts of degradation products were present. The highest value for total radioactivity found in the nectar corresponded to 2–7 p.p.m. expressed as demeton‐S.Radioassay of treated leaves and new growth after spraying confirmed that demeton‐S is rapidly con, erted in the plant into two primary degradation products extractable by chloroform. Further breakdotvn is more rapid in new growth and appreciable quantities of the two primary products believed to be biologically active are retained by the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02467.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Organo‐phosphorus residues in tissues of sprayed plants were detected by estimating the esterase‐inhibiting activity of their leaf and root extracts. This method was used to examine the anti‐esterase effects of mangold plants that had been sprayed with Systox, parathion and Hanane. Extracts of leaves of these treated plants were shown to inhibit added choline esterase for some weeks after treatment. The enzymic hydrolysis of phenyl acetate by extracts of leaves and roots of mangold plants treated with these insecticides was reduced for varying periods of up to 8 weeks.Assays of parts of bean plants that had been sprayed with demeton‐S showed that anti‐esterase activity was limited to those parts that had been sprayed: tissues developed subsequent to spraying showed no such effects. Leaves sprayed about z months previously inhibited added choline esterase and showed reduced activity in hydrolysing phenyl acetate. There is some evidence that substances, possibly substrates in the plant enzyme systems affected, accumulate in treat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02468.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The narcotic and toxic potencies of the first seven homologous alcohols and the methyl esters of the first seven homologous fatty acids have been determined using grain weevils(Calandra granaria).The experiments were designed as balanced incomplete blocks, and Finney's probit plane technique was applied to the results. In both series of compounds the narcotic and toxic potencies expressed in thermodynamic concentrations decreased with increasing number of carbon atoms. The margin between narcotic dose and toxic dose is greater in the alcohol series than in the ester series. The methyl esters of the fatty acids showed a stepwise descent in biological potency, the odd numbered series being more active than the even series. The penetration of these compounds into grain weevils and their biological action are discussed in relation to the coefficients of response to log concentration and log time of exposure.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02469.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Pyrethrin‐treated flour beetles,Tribolium castaneum(Herbst), lose weight rapidly. The weight lost by batches of beetles, a readily determined graded response, has been investigated with a view to its use in bioassay. Strong evidence was obtained that (1) in pyrethrum extracts only the pyrethrins cause the loss, and that (2) the other extractives do not modify the loss caused by the pyrethrins. Allethrin also caused a rapid weight loss; piperonyl butoxide, by itself producing little loss, greatly increased the loss caused by pyrethrum solutions and by allethrin, paralleling its effects on toxicity. The pyrethrin content of solutions appeared to account quantitatively for their weight‐reducing activities; irradiation of pyrethrum solutions that destroyed their toxicity also destroyed their weight‐reducing properties; and neither pyrethrum oleoresin heat‐treated to destroy the pyrethrins, nor irradiated solutions, modified the weight loss due to allethrin.Factors influencing weight loss were investigated. Beetles were exposed, mostly for 3 hr. at 25°C., on hard filter‐papers treated with solutions of pyrethrins in a non‐volatile oil (Shell Risella oil 17, formerly called P31). At fixed deposit the loss rose sigmoidally with increasing pyrethrin concentration from about 0.7 % for zero concentration to an upper limit of about 6.5 % of initial beetle weight. A log‐logit transformation made the sigmoid curve linear. The carrier oil and the length and temperature of the exposure to the pyrethrins influenced the weight loss. At 25°C, the rate of air movement and the relative humidity between 40 and 90% did not. Pyrethrins in Risella oil 17 could be applied satisfactorily to the filter‐papers by means of a spraying tower, or by pipette if the solutions were first diluted with a volatile solvent, which was allowed to evaporate subsequently. Deposits of given pyrethrin content were about 1.3 times as active in producing a weight loss if prepared by spraying than if prepared by solvent evaporation.The technique, design, and analysis of results, for bioassays based on weight loss are described. The most elaborate method of analysis ever likely to be needed is given, with a worked example, but a considerably simpler method, only slightly longer than the probit analysis for quantal‐response assays, would probably suffice normally.For a given number of beetles used, the weight loss method of assay has about the same inherent precision as the film method of Parkin&Green (1943), but is less precise than the direct spray method of Hewlett (1947). However, larger numbers of beetles can be used in the new method, the assessment of the insecticidal effect is more objective, and results are obtained more quickly y‐BHC and DDT cause T. castaneum to lose weight less rapid

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02470.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The distributions of the periods of survival of individual rainbow trout in solutions of potassium cyanide are asymmetrical and approximately log‐normal within the range of concentration where the relation between log time and log concentration is linear, whereas they are symmetrical and approximately normal at higher concentrations.Some inherent, persistent features possessed by the fish influence survival time in both the higher and lower ranges of concentration, but other such features exert a significant influence only in the lower concentrations.Some of the features influencing survival time in the lower concentration range only, are associated with body siz

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02471.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Periods of survival of rainbow trout in concentrations of un‐ionized ammonia in the range 0.86‐1.96 parts per million of nitrogen increased as the concentration of dissolved oxygen was raised from 1–5 to 8‐5 p.p.m.At each concentration of dissolved oxygen the period of survival decreased as the concentration of un‐ionized ammonia increased from 0.86 to 1.96 p.p.m.The effect of oxygen in increasing survival time was greater in the lower concentrations of un‐ioni

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02472.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The effect of commercial trapping on two rabbit populations in West Wales, was investigated during 1946 to 1949. On two farms rabbits were caught alive in snares, marked and released just before trapping; the total number of rabbits marked, divided by the fraction of marked rabbits recovered in the trapped sample gave an estimate of the population before trapping started. Trapping usually removed 30–40 % of the rabbits present, a proportion compatible with a careful cropping of the population. At one farm, studied for 3 years, the population increased steadily.Breeding was intense from January to June inclusive, and from weight and age distributions it was apparent that in 1948 and 1949 considerable breeding also occurred in autumn. The sex ratio varied around a mean of about 50%.Data are given on movements, obtained from recapture records of zog marked animals. They suggest that rabbits probably forage over an area of not more than 150 yards in diameter. The records from recaptured marked animals indicate that the mean expectation of life is about 6 month

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02473.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

A successful experiment in rabbit control was carried out over one year on a 300‐acre farm in Pembrokeshire. The control measures adopted were trapping, gassing and ferreting, in that order. Information on rabbit density was based primarily on counts of rabbit holes and on the number of animals caught. Observations were made on the breeding state and sex ratio of the population. Successful control was attributed to the persistent application of a variety of methods, and not to any one method in particular. Gassing was equally efficient on high and low rabbit populations; the three methods of application, namely pumping, spooning and a combination of both, were found to be equally effective. Re‐infestation occurred, but was checked to some extent by trapping around the boundary.The breeding season appeared to extend from January to June, inclusive. The sex ratio was biased in favour of females throughout the experiment. An almost even sex ratio was observed in embr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02474.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The rate of CO, production per g. dry matter of the younger leaves of tobacco plants systemically infected with tobacco mosaic virus was about 10 yo less than that of comparable healthy leaves. Older infected leaves, showing well‐developed mosaic symptoms, had the same respiration rate as comparable healthy leaves. These results were independent of seasonal change in light conditions during the growth of the plants. Older leaves, but not younger leaves, of infected plants had a lower initial water content, and both absorbed less water during the experimental period, than leaves from healthy plants. The effects of TMV infection on water content were so great that the rate of CO, production per g. fresh weight was sometimes significantly increased by infection. This reversal of the apparent effect of infection on respiration rate, depending on the basis of reference may partly account for contradictory results reported previously by other workers. Other causes for contradictory results are discusse

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02475.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY