The ploughing of a permanent pasture in spring was not followed by a reduction of the earthworm population during the first 6 months but further arable cultivation did greatly reduce the population. Leys, 4–7 years old, carry a total population similar to that of permanent pastures, but with differing proportions of certain species. Some trends in population changes during a period of nearly 1 year are described for five common species. The population of a permanent pasture did not show appreciable change for a period of nearly 3 years but that of a ley, in its first year following arable, showed a significant increase.

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Changes in the seasonal activity of several species of earthworms have been followed in a permanent pasture field for 18 months, 1945-6. The two soil conditions which chiefly determine activity are temperature and moisture. Other factors are the occurrence of an obligatory diapause in the two species Allolobophora n o c t m and A. longa, and changes in population in A. chlorotica and Lumbricus terrestris.Soil temperature and soil moisture also determined the weight of soil thrown up in the form of wormcasts during autumn, winter and spring. It is suggested that only two species, A. nocturna and A. longa, are responsible for wormcasts and that the other four common species present play little or no part in this activity.At Rothamsted it was found that the previous agricultural history of the field is an important factor in determining the fauna. Old permanent pasture is characterized by a high percentage of A. nocturna and a rather lower percentage of A. caliginosa. Ploughing old permanent pasture and reseeding to grass after I or z years arable reduces the proportiom of A. nocturna and A. caliginosa and increases that of Eisenia rosea. 4rable fields have A. chlorotica as the dominant species and pasture fields z7years grass after many years of arable farming still show a high percentage of A. chlorotaka and a low proportion of A. nocturna.A survey of the Carse of Stirling, Scotland, showed that soil type is also an important factor in determining the earthworm fauna. A. cdgfmsa was the dominant species on the three soil types studied, but the subdominant species varied. On clay soil, A. longa was subdominant; on loam, A. longa and L. d e l l u s ; on sandy soil, A. longa, L. rubellus and A. chlorotica. The dominant species of pasture land at Rothamsted, A. nocturna, was not found at Stirling.

Rosette disease of groundnuts in Tanganyika is brought into the crop by infective alatae of Aphis craccivora: spread within the crop is by apterae and alatae. During the dry season the aphids maintain themselves on self‐set groundnuts and on two genera of Leguminosae: Vigna and Millettia or Lonchocarpus. No native source of the virus causing rosette disease has been discovered, but self‐set groundnuts carry over the virus from one cropping season to the next. Syrphid larvae and other predators are important in controlling the vector. Preliminary spraying trials with 0.5% schradan gave promising results in controlling the aphids on groundnut crops and consequently checking the spread of rosette disease. Selections of the variety Mwitunde showed the lowest incidence of rosette infection and gave the highest yields in trials in 1952.