The beetles dealt with here were collected while I was acting as entomologist to the Percy Sladen Trust Expedition to Lake Titicaca in 1937. They were all taken on the floor and walls of a room in which Nepal barley was stored. The room—later cleared of grain and used as a dining room—was in the hacienda Camjata, Capachica Peninsula, Lake Titicaca, alt. 3,850 m. The walls were made of adobe (sun-dried brick) and the roof was thatched with Scirpus tatora.

1. A number of generations of Dysdercus howardi, Ballou, bred in the laboratory between 1932 and 1934 are compared with a similar number of generations bred from 1940 to 1941.

2. There is found to be no significant difference in the length of the life-cycle in the two periods.

3. There is a significantly greater number of adult female insects in the earlier generations of D. howardi (eleven generations).

4. In the later generations there is a higher percentage of infertile eggs. The difference between the two groups of insects is highly significant.

5. There is no significant difference in the percentages of nymphs becoming adult in the two periods.

6. The differences in the numbers of adult insects and in the sex ratios obtained in 1932–34 and 1940–41 are found to be non-significant (twelve generations).

The work which resulted in this paper was carried out in the Department of Entomology of the British Museum (Natural History) at the request of Professor J. W. Munro and on behalf of the Pest Infestation Laboratory of the Department of Scientific and Industrial Research.

Large numbers of the bat, Nycteris hispida, Schreber, have been observed at dusk flying out of the residual forest islands at Gadau. Some have been captured and placed in a large cage containing Glossina morsitans and G. tachinoides. The sleeping bats, hanging head downwards, are perfect complacent hosts; both species of tsetse have been seen to attack and feed on them on many occasions, and to experience no difficulty in becoming fully gorged.

In the British Museum (Natural History) Ruwenzori Expedition 1934–35 vol. II nos. 3 (1939) and 4 (1940) generic keys to the Muscinae and Coenosiinae and specific keys to Graphomyia, Musca and the Coenosiinae of the Ethiopian region have been published. As there seems no possibility of the Museum issuing any more of these reports in the near future, it has been agreed that suitable extracts from the manuscript of the third part be published in this Journal, so that the keys and some other necessary data shall be available for the use of Entomologists in Africa.