A previous paper in this Bulletin dealt with the economic entomology of the British Solomon Islands Protectorate up to the year 1932. The present article concerns research conducted after that date with special reference to the biological control of two insect pests.

These crops are all either indigenous or of early introduction, except in the case of special varieties and they have achieved within the limits of their present distribution an equilibrium with their insect pests. Where there is no reasonable chance of a return for his labours, the native has ceased to grow a particular crop. This equilibrium is unstable, since pests increase in numbers at intervals owing to a variety of causes. For example, the introduction of cassava into new areas to prevent famine during the locust invasions brought to light the stem-borer moth, Opogona chlorophanes Meyr. In some cases cassava could not be grown and sweet potato had to be substituted. Acridids such as Eupropacris uniformis suddenly appear in great numbers at long intervals and do. considerable damage, then disappear just as suddenly. Similarly the adverse effect of climate on the crop will render it susceptible to particular pests, especially Aphids, during periods of drought. Agricultural practice is also concerned in this equilibrium, as for example where the time of planting legumes is governed by the attacks of various Galerucid beetles, particularly Ootheca bennigseni, Wse., which are most active during the early rains.

1. All polysaccharides fed to Melanoplus have been utilised incompletely or not at all.

2. Rupture of the starch granule renders it partly utilisable.

3. Glucose, galactose and xylose are completely absorbed.

In summing up the results of our study of the local varieties of maculipennis in a region of Macedonia, we have tried to deal with the region as a thing by itself, without allowing ourselves to be influenced by what we might know regarding the varieties of maculipennis found elsewhere.

We found a maculipennis nearly uniform throughout the whole region as regards habits and morphology, and not varying greatly except with respect to one character, the sculpturing of the eggs. On the basis of this character, we may make two groups, provisionally called typicus and messeae, but we must use statistical methods to establish these two groups, for we find much variability in them. The amount of variability is not uniform over the whole region; in some localities the egg-type is nearly all typicus, in others messeae greatly predominates. Our problem has been to test the validity of this characteristic, especially with regard to its persistence from parent to offspring and its constancy in varying environments.

In the course of studies of the behaviour of the tsetse-fly, Glossina morsitans, certain facts of considerable interest concerning its phototropic reactions have been established.

It is considered desirable to place on record some data relating to insects attacking economic plants in Sierra Leone; little information has hitherto been available, and it is hoped that this list will prove of interest and use to other workers. Families, genera and species are arranged alphabetically.