In 1950 I received from Mr. D. Hille Ris Lambers a strange Pseudococcid from Java which had been collected by Mr. F. W. Rappard, a senior forestry officer, who regularly collects aphids for Mr. Hille Ris Lambers on his tours of duty. As this insect was a coccid, it was transmitted to me for examination. Its appearance is quite abnormal; the shape of its body reminds one almost of a large mite (fig. 4). The 6-segmented antennae have a dense vestiture of fine hairs, with exception of the 2 first segments which are very short. A tuft of 5 very long setae is present on the top of each of the anal lobes. The ungual digitules are extremely large and very flat. It was only after close study that the insect was recognized as a Pseudococcid. It has 2 pairs of ostioles in the usual position, a circulus on the ventral side of the second abdominal segment, and a few trilocular pores on both sides of the body. As I suspected an abnormal mode of living, I asked Mr. Hille Ris Lambers to write to Java for further particulars, and more material. To comply with this request Mr. Rappard has collected abundant material and communicated his field notes on these insects, which he calls "ant-riders" from their peculiar habit of climbing upon the black ants by which they are closely attended, as soon as these ants are disturbed, to have themselves transported in this way. The material at hand contains 3 different instars which seem to represent first and second stage larvae, and immature adult females. Of the latter stage only 3 specimens are available. Eggs or embryos were not observed in these specimens, but in one of them the oviduct and its exterior opening (one segment behind the posterior ostioles) is faintly visible in the chitinous