vu 
for microscopical study will be discussed. Since the distinguishing character- 
istics rest chiefly with microscopical structure, great care and close attention 
should he given to technique. 
Terms used in discussion. In addition to the glossary found at the back 
accompanying the index, a brief preliminary discussion of terms may tend toward 
a better understanding for the beginner. 
Scale has reference to the covering of the insects belonging to the 
Diaspinse. In removing an insect of this family from its host, it will be 
observed that a scale or covering comes off apart from the body of the insect, 
and that beneath the insect there is frequently a thin whitish layer. This is the 
under part of the puparium and is known as the ventral scale. The part covering 
the insect is designated as the dorsal scale. In this work the term scale is some- 
times used unqualified. In such cases it refers to the dorsal scale. In the 
Diaspina; the last abdominal segment, frequently called the pygidium, bears the 
stable distinguishing characteristics. The lobes, plates, spines, circumgenital and 
dorsal glands are illustrated in the accompanying diagrammatic figure (fig. a), 
showing their relative positions in the genus Chionaspis. I’pon these rest the 
h ' 
Fig. a. 
Diagrammatic plan of pygldlnm of Dlo'^pina), typical of the genua Ghlonaspla. A. median apace, 
jB, C, D, K. y’, first, second, third, fourth, and baaal spaces respectively. At the base of A la the circu- 
lar anal opening ; the transverse line jnat below Is the genital opening. Grouped glaiida (spinnerets) 
In D are the median, In C the anterio-laterul, In D the poaterlo-iateral. — all on the ventral surface, 
o, 6, o, d, c, etc., are simple plates; in many of the Diaspina* these are toothed. 1, 2, 3, 4, 6, etc., are 
spines on the dorsal surface. The dttrsal pores are arranged in rows In D, K, and F. The median 
lobes are at the candal extremities of B. the notched or cleft second lobes are at the caudal extremi- 
ties of C, the third pair of lobes are similarly located and ntttched In D. 
chai'iictcrist ics which tiic to bo most depended upon in the study of differentiation. 
The scale itself is an unstable character in the Diaspina*. In the Decaniinie, as will 
be seen, the ehitinous covering is more constant. The relative values in tlilVereu- 
tiation of these various structures are discussed under the species enumerated. 
Clnssifirulion. The separation into subfamilies of the family Coeeida* differs 
with different authorities. Signoret arranges the genera and species under four 
divisions. (Jreen groups them under ten subfamilies, and Cockerell under eleven. 
It is not within the province of this article to enter info the merits of the various 
systems, but simply to refer to those subf .milies under which the species herein- 
