ae 
1 June, 1898.] QUEENSLAND AGRICULTURAL JOURNAL. 499 
and four terminally thickened bristles (that enable it, unlike its parent, 
to erawl freely about), and a hair-like suctorial mouth organ (Fig. 5b). The 
young of both sexes are alike both in form and habit, and in being exceedingly 
frail and readily injured insects. After a few hours’ wandering about they 
become stationary, and having inserted their probosces into the underlying 
plant tissue settle down. Tig. 6 represents the recently fixed larva, and Figs. 
7 and 8 the successive outward appearances that are presented by it and that 
are accounted for by the covering of felted waxen whitish threads with which, 
in a few hours, it completely covers itself. Whilst in this condition the insect 
may be recognised by aid of the lens; appearing asa pinkish white ball (shown 
in some instances on Plate XL. Beneath this covering, after twelve days 
from birth have elapsed, the insect molts its skin, and with it both legs and 
feelers. Plate XL, fig. 9, represents a view of the larva of the male after 
this first molt. Hitherto the male and female insects have been quite alike, but 
distinguishing features between the two may now be recognised; though for 
some time still the scales themselves are outwardly similar, being in both cases 
circular in outline. In the case of the male a second molt gives rise to a 
so-called pro-pupa stage, and a third to a pupa one (Plate XL, fig. 10), and. 
from this in due course issues a two-winged fly, the adult male; meanwhile the 
seales proper have developed different shapes—that of the female being 
circular, that of the male oblong. The female insect molts but twice; its 
discarded skins or exuvie being placed in the centre of the secreted matter that 
largely composes the scale, instead of in one side thereof as in the male. With 
the second molt the male insect loses its mouth organs, and so ceases to secure 
fresh nourishment, but these persist to the last in the case of the female, that 
thus feeds throughout its entire life. Thirty days from birth the females are 
full grown, and from three to seven days later begin to produce young. When 
a female insect has been once visited by a male one, many successive 
generations may arise parthenogenetically, as in other scale insects, without 
further union of the sexes. : 
_ As previously, remarked each female occupies on an average six weeks in 
giving birth to its 400 larvie, but before the last have issued the first born in 
their turn haye produced young, and this is followed successively by a similar 
event on the part of the younger and still younger progeny; so the broods 
become very greatly intermixed.* 
To demonstrate the rate of increase manifested by the Pernicious Scate, 
“ series of experiments were performed by the Division of Entomology, 
Department of Agriculture, U.S.A., at Washington, in which one over-wintered 
female was placed upon each of seven trees, and when the offspring of these 
seven were mature all were removed, save one fertilised female on each tree, 
and the same process repeated until the cold weather closed the breeding 
season. ‘From accurate observations upon these experiments, it was estimated 
that, if all the young of one over-wintered female live, the increase from this 
one and her progeny for the one season would be 8,216,080,400. ‘These would 
be the descendants from a single insect in a single season, if all fulfilled their 
functions in life. While it is hardly to be expected that all should live, yet 
granted that a goodly number should perish prematurely, even then it is readily 
seen that enough survive to explain the sudden destruction of trees attacked.” 
—(S. J. Hunter, XVI, p. 14.) 
“Tam satisfied (writes F. M. Webster, Indiana Horticultural Report, 1896, 
p. 12) that a tree, starting with half-a-dozen young females ready to give birth 
to young, if nothing be done to stay their ravages or to prevent their unre- 
stricted increase, will be killed down in four or five years, no matter what the 
soil may be or how vigorous they have been at the commencement of the season.” 
Tt has been observed with regard to the occurrence of the San José Scale 
in the United States that reproduction ceases during the winter months, until 
the latter part of May, during which the insect remains semi-dormant in a half 
* The above facts relating to the life history of thé'San José Scale have been obtained from 
the special memoir (X.) by L. O. Howard and C. L. Marlatt, already referred to. : 
