Since the appearance of the first paper in this proposed series our attention has been called by Mr. E. E. Green to the desirability of developing a terminology for the various structures of the Diaspid scales which shall be more satisfactory than that at present in general use. We are entirely in accord with his view that many of the terms at present employed are not suitable and that they need to be replaced by others of more precise application.

We have decided, however, not to make any attempt at the development of such a terminology at the present time, the controlling reason for this decision being found in the belief that the morphology of the Diaspid scales—not to speak of the other groups—is still too insufficiently understood to permit the formulation of a terminology which shall be at all enduring. It is our belief that any system now devised is too likely to require extensive later modification. This is certainly the case with one recent attempt thus to devise such a system, an attempt that fails of its purpose because of lack of knowledge. From this point of view it seems best to leave the question of such a terminology until such time as at least a large proportion of the Diaspid types have been examined in greater detail.

For the present we shall content ourselves with the use of common and, in general, well understood terms or with simple descriptive phrases. An exception will be made in the case of certain terms which it seems well should be eliminated as soon as possible. One such term is the expression “ pygidial lobes ” for the usually paired structures of the pygidial margin. For these Mr. Green suggests that the term “ trulla,” which has already been employed by some authors, is better. Another substitution suggested by Mr. Green is that of “ perivulvar ” to designate the cluster of pores about the genital opening, and this we shall utilise.