摘要:

A cytoplasmic polyhedral virus exPhalera bucephala(L.) induces a polyhedrosis in some stocks ofPieris brassicae(L.). Larvae from different localities vary in their susceptibility to their own viruses and the stock ofPieris brassicaelarvae most susceptible to its granulosis is also more susceptible to the polyhedrosis.Polyhedra obtained fromPieris brassicae, infected fromPhalera bucephala, did not cause a cytoplasmic polyhedrosis in larvae ofPlutella maculipennis(Curtis) andPseudaletria unipuncta(Haw.), but did do so in the larvae ofLymantria monacha(L.).

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02528.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Sampling for stem‐boring larvae was undertaken in 1954‐56 on ley plots ofLolium perenne, Dactylis glomerata, Festuca arundinacea, F. rubra, Agrostis tenuisandPoa pratensisin randomized experiments at Hurley, Berks. The samples showed infestations by dipterous larvae, mainly species ofOscinella, MeromyzaandOpomyza.The larvae showed preferences for specific grass hosts. More larvae were found where plots had been grazed throughout the season than where an early hay cut had preceded grazing. The total numbers of larvae varied between o and 688 per sq.yd. in November.The larval populations of the leys were reflected in the populations in winter wheat which followed the plough‐up of the leys. Populations of up to sixty‐five larvae per sq.yd., mostly species ofOscinella, were found in the wheat in March. In 1956 a heavy larval infestation was associated with the death of considerable numbers of wheat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02529.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

A study was made of the relationship between rate of flow of water through sands of different particle size and the downward velocity of eelworms of various lengths and activities. The relationship between rate of flow of water and velocity of eelworms is not linear. For rates of flow less than about 500 cm./hr. the velocity of the eelworms relative to the velocity of water is greater than for flow rates greater than about 500 cm./hr. For rates of flow greater than 500 cm./hr. an equation is derived which relates velocity of eelworms, rate of water flow, length of eelworms and pore diameter in the sand. The following facts were established: the velocity of the eelworms increases as pore diameter increases; the velocity approaches zero when the eelworms' length exceeds four times the pore diameter; the relationship between velocity of eelworm and velocity of water is independent of the eelworms' own activity; the equation of eelworm movement is valid for both continuous and discontinuous saturated flow. With flow rates less than about 500 cm./hr., the velocity of the eelworms increases as the eelworms' activity increases and eelworms appear to pass through smaller pores than at high flow rates. Dead or inactive eelworms do not progress very far in sand even at high flow rates and observations suggest that slight flexing movements of the eelworm body is essential for passage.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02530.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

A technique for conducting hatching experiments on eggs freed from cysts is described. The form of the hatching response was found to be similar to that of eggs contained within cysts, but the response of the free eggs to the hatching stimulus was slightly more rapid. Investigations into factors affecting free egg hatching showed that it was necessary to presoak cysts before extracting the eggs from them for hatching. Eggs taken from dry cysts or from cysts that had been opened or cracked before presoaking did not respond to diffusate. When free eggs and whole cysts were exposed to the same graded series of dilutions of diffusate, the L.A. values (i.e. log concentrations of hatching factor) derived from plotting the hatching curves were in very close agreement.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02531.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Solitary house mice confined in a large pen were supplied with wheat in wooden trays distributed evenly throughout the area, and the number of grains removed daily from each was counted. A mouse tended to feed sporadically over the whole area, but feeding was more intense at a few trays, not necessarily near the nest, and not the same on successive nights. When new sources of the same food were introduced a mouse tended to patronize them during the first night. At the same time there was a significant drop in the number of the old trays visited. This suggested that new food sources stimulated investigation rather than avoidance.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02532.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Barley and white persicaria (Polygonum lapathifoliumL.) were grown in pure and mixed populations of varying density in sand culture in a glasshouse. The leaf areas and dry weights of leaves, stems and roots were determined at intervals. During the phase of vegetative growth the addition of dry matter by barley was unaffected, although tillering was reduced, by competition from dense stands of white persicaria, whereas the growth of white persicaria was reduced by low densities of barley. The decline in leaf area and reduction in root growth of barley with the onset of flowering was accompanied by increased growth of white persicaria with the production of branches from the upper axillary buds. These flowered and set abundant seed. This behaviour probably accounts for the persistence of this weed in arable rotations.The greater competitive ability of barley may be attributed to its larger embryo, giving much larger plants at emergence. The intrinsic relative growth rate of white persicaria is as high as, or higher than, that of barley and falls more slowly with time. This advantage is not sufficient to offset the initial differences in size while barley is vegetative. The larger embryo size of barley also determines the more intense competition that exists between plants of this species than between plants of white persicaria at similar densities and times from germination. With equal weights of produce per pot (or unit area) the intensity of competition within each species appears to be similar.It is emphasized that the course of growth with time, rather than weight‐density relationships at given points of time, must be followed in order to understand the influence of density. Two functions of the relative growth rate with time are examine

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02533.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

The physiological activity of complete series of mono‐ and di‐substituted chloro‐and methyl‐phenoxyacetic and benzoic acids have been investigated using the wheat cylinder, pea segment and pea curvature tests. In the phenoxyacetic acids, high activity was associated with substitution in the 3‐, 4‐, 2:4‐, 2:5‐ and 3:4‐positions and in general, chlorine had a greater effect than methyl in conferring activity.With the benzoic acids, 2:3‐, 2:5‐ and 2:6‐, disubstitution gave active compounds, the chloro‐derivatives again being the more active. The 2:5‐compound was the most active in the dichloro‐ series, all members of which were less active than the 2:3:6‐trichloro‐ and 2:3:5:6‐tetrachloro‐acids. Benzoic acids substituted in the 4‐ position were either inactive or exhibited only weak growth‐promoting activity.The results are discussed in relation to recent theories which attempt to relate growth‐promoting activity with the po

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02534.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Book reviewed in this article:Histological Technique. H. M. Carletonand R. A. B. DruryRadioisotopes in Scientific Research. Vol.iv.Research with Isotopes in Plant Biology and Some General Problems. R. C. Extermann.Chemical Aspects of Ecology in Relation to Agriculture. HubertMartin.Methods of Testing Chemicals on Insects. H. H. Shepard.Beneficial Insects. B. D. Moreton.The Grafter's Handbook (2nd edition). R. J. Garner.Common Names of British Insect and other Pests. Compiled by I. Thomasand H. W. Janson.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02535.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY