Two leaf miners of coffee, Leucoptera coffeella and L. caffeina are present in the Kilimanjaro and Usambara districts of Tanganyika. The life-histories of L. coffeella and its parasites and a study made during 1937–40 of the populations of the host and its parasites in the Kilimanjaro area in both unshaded and shaded coffee are described. Some observations are made on the “dominant stage” of the host.

A description is given of the bionomics of Leucoptera caffeina Wshbn. in the Kilimanjaro District, Tanganyika, and of the characters that distinguish it in its various stages from L. coffeella (Guér.), together with the results of population studies of the former insect and its parasites in both shaded and unshaded coffee in 1938–40.During the 1939 outbreak, the numbers of eggs per tree, and the number of live pupae present in samples of about 100 cocoons (estimated from te number of moths and parasites emerging) showed large fluctuations. The times between peak numbers approximated to the total life-cycle, indicating that at any moment one developmental stage was dominant.

Throughout the world, wheat bran seems to have been the most popular carrier for locust and grasshopper baits. Wheat bran has, however, always been difficult to obtain in East Africa in sufficient quantity for large scale campaigns, and wartime conditions coinciding with a large outbreak of Schistocerca gregaria have made the position even more acute.

During the testing of finely ground pyrethrum flowers as an insecticide for the control of Antestia lineaticollis, Stål, in coffee trees, it was noticed that the various instars showed different percentage death rates under the same conditions. The experiment which is dealt with here was primarily designed to discover the minimum effective dose of powder per tree, and was carried out as follows.A block of 1,700 coffee trees was divided into seventeen square plots each containing 100 trees. Nine of these plots were treated with pyrethrum powder at rates varying from about 1 gram to 5 grams per tree; all the trees in the same plot receiving the same amount of powder. Two days later 36 trees from each of these plots, comprising all the trees from the centre of the plots (the two outer rows of each plot not being used in case migration of the Antestia should have taken place from the adjoining control plots) were heavily drenched with a strong kerosene extract of pyrethrum in order to bring down all the Antestia remaining on the trees; these Antestia were collected separately for each tree, sorted into instars and recorded. This method of testing is described fully by Le Pelley (1934).In each of the eight control plots five trees selected at random were drenched with the kerosene extract of pyrethrum and the Antestia obtained were recorded in the same way. It was found that the average number per tree of Antestia and of each instar present in each of these control plots, which were themselves evenly distributed through the whole block, was practically constant. It was therefore assumed that the numbers of Antestia and of each instar was the same for the plots treated with pyrethrum prior to this treatment, and the number of each instar found on the trees after treatment subtracted from this figure represented the number which had been killed by the pyrethrum powder.

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