Bugs, Cicadas, Aphids, and Scale-insects 185 
it was found that at Washington four full generations are regularly developed, 
with the possibility of a partial fifth generation. On a number of potted 
trees a single overwintered female was left to each tree. After the full 
progeny of this individual had gone out over the tree all were removed 
again, except one of the oldest and fertilized females. This method was 
continued for each generation throughout the breeding season. Some 
interesting records . : . were thus obtained, which indicate the fecundity 
of the females as well as the number of generations.” 
From these records it may be fairly estimated that an average of 200 
females (in addition to about as many males) are produced by each female, 
and that there are four generations each year in the latitude of Washington, 
D. C. Thus the product of a single overwintered female in a single year 
amounts to 3,216,080,400 male and female descendants. This total is, 
of course, never reached, because only a part of each generation reaches 
maturity and produces young, but in a favorable season on a tree newly 
infested (and thus providing a plentiful food-supply) a large majority of 
each generation do most probably go through their normal existence. 
“Neither the rapidity with which trees become infested,” add Howard and 
Marlatt, “nor the fatal effect which so early follows the appearance of this 
scale-insect is therefore to be wondered at.” 
But not all scale-insects are so specialized either structurally or physio¬ 
logically as the pernicious (or San Jose) scale. The females of some species 
retain the eyes, antennae, and legs through their whole life and can crawl 
about if need be at any time. Others show a sort of transition between 
these two extremes of activity and quiescence, having the legs present, but 
in adult life much reduced in size and probably functionless, or at best 
capable of carrying the insect but feebly and briefly. In the matter of the 
covering, too, there is much variety; some scales secrete no wax at all, but 
have the body-wall of the back specially thickened and made firm so as 
to act as an effective covering-shield underneath which, somewhat as with 
a turtle, the legs and head can be concealed. Others secrete filaments or 
tufts of soft white wax which form a sort of felted protecting covering for the 
body. In a general way the various scale-insects may be instructively 
gathered into three groups, depending on the characters of the females; 
in the first group the females retain the antennae, eyes, and legs, and the 
segmented condition of the body (typical of normal insects) and are capable 
of locomotion throughout life; they secrete wax usually in the shape of white 
cottony filaments or masses with which they cover the body more or less 
completely, sometimes forming conspicuous waxen egg-sacs at the posterior 
extremity of the body; the females of the second group retain their legs 
and antennae through life, but have them in reduced condition when adult, 
and although capable of feeble motion, usually lie quiescent; they commonly 
