Biological notes on Dasynus manihotis Blöte

In June 1932 we received at the Institute for Plant-diseases at Buitenzorg (Java) a number of Coreid bugs, sent by the Adjunct Agricultural Adviser stationed at Wonogiri (Res. Djocjacarta, Central Java), which bugs were reported of causing rather serious damage to Cassava plants (Manihot utillissima Pohl) ; the sending included some damaged plants. The Coreids were sent for identification to Dr. H. C. Blöte, curator of the Leiden Museum, as it was known to me that he was studying this special group of Heteroptera. Recently Dr. Blöte (1935) described the species sent as Dasynus manihotis. It is closely related to another noxious species of Dasynus, some years ago described by China as Dasynus piperis, which is well known by the studies of Dr. J. van der Vecht (1933). Character of the damage. Dasynus manihotis sucks the top parts of the stems of the Cassava plants. Its punction causes the tissues to shrink and the leaves to wither. Soon after the punction the shrunken tissues take a brownish colour, later the leaves wither entirely and drop, and the stems that are much punctured die off. New leaves can develop from the lower part of the stem, but in the meantime growth is much retarded. The illustration (fig. 1) gives a good impression of the damage in its earlier stage. The irregular sunken patches in the lower part of the stem have a light tobacco to chocolate brown colour. The smaller spots between the second and the third small leaves from below are pale brown. Experiments in the laboratory on healthy plants gave the same symptoms. Bionomical notes. The egg is 2 mm long. It is figured on approximately natural size (fig. 2) and enlarged (fig. 3). The colour is pale