On May 23, 1929 a species of Phenacoccus was found in ant's nests of the genus Lasius. Some of these were feeding on the roots of grass and were well guarded by the ants. Mature males were also found in the nest. After going carefully through the literature I find that it agrees well with the description of P. wilmattae Ckll. However, since a number of very obvious characters were omitted in the original description it will be profitable to mention them, and emphasize the outstanding differences between this species and P. stachyos Ehrhorn.