127 
different generations for the year, the product of a single individual from spring to fall 
amounts to 1,608,040,200 females. In one instance we have over 415 males from a single 
female, and while the number of males would average somewhat less than the females, taking 
the summer through, yet, having underestimated the females, the males may be estimated at 
the same number, giving a total of 3,216,080,400 descendants from a single insect in a single 
season. It is not to be expected, of course, that all the individuals from a scale survive and. 
perform their function in life, but under favourable conditions, or in the case of a tree newly 
infested, or not heavily encrusted, the vast majority undoubtedly go through their existence 
without accident. Wherefore neither the rapidity with which trees become intested, nor the 
fatal effect which so early follows the appearance of this scale insect is therefore to be 
wondered at.* 
With reference to the nature of the injury occasioned by Seale Insects to 
plants, it may be remarked that there are grounds for concluding that this does 
not exclusively consist in the extraction of so much cell-sap, and the 
consequent deprivation of the vegetative or reproductive parts of the service 
that it should otherwise render them. ‘For they no doubt originate also 
chemical changes that may have more than a local prejudicial effect. Inthe case 
of many of the Armoured Scales it may be commonly remarked that the foliage 
that is infested by a particular species has its green colouration in great 
measure discharged at spots where individuals are attached. The San José or 
Pernicious Scale when it occurs on either the apple or the peach—and the 
observation is applicable to fruit as well as foliage—oceasions a very distinct 
reddish-purple spot. Again, other Scale Insects—e.g., Mealy Bug (Dactylopius) 
often occasion contortion of foliage where they occur, whilst others give rise to 
galls. These phenomena, it is considered, do not merely arise from mechanical 
influences due to the feeding habit, nor can they. be attributed to atmospheric 
agencies brought into injurious relation with the tissue of the plant as 
@ consequence also thereof. Again, it may be inferred from observation also 
that there is a special condition of the plant ceteribus paribus favourable 
to the increase of whatever scale insects may accidentally become established 
upon it.f 
__ There is, in conclusion, another form of injury that may be ascribed to 
certain Scale Insects, though not, it is true, exclusively arising from their 
presence. ‘This consists in the occurrence upon plants infested by them of a 
more or less dense black investment that may even extend to the ground 
beneath their branches. The presence of this is accounted for as follows :— 
These Coccidex possess the habit of excreting forcibly from a special terminal 
organ a gummy saccharine fluid that may be shed over the entire surface of 
the leaf immediately beneath that upon which they are stationary, or even upon 
the bodies of their fellows located thereon. This sweet substance on its part 
forms a congenial home for, and is soon occupied by, more than one 
species of epiphytal fungus. These, that are characterised by the possession of 
almost black or rather dark olivaceous spawn threads and reproductive organs, 
constitute, when growing thickly together, a soot-like encrustation that bears 
the appropriate name of “ fumagine” (Lat., fumago, soot), and that may be 
recognised on scale-infested trees, even when the observer is located at a 
considerable distance therefrom.t This habit is manifested by Mealy Bugs, 
by Wax Scales (Ceroplastes spp.), and several other generic forms, but especially 
by the various species of Lecanium, though not equally so by all. The special 
organ associated with this habit is represented on Plate ILL., Figs. 11 and 12. 
In Fig. 11is shown (a) the termination of the intestine or rectum, (0) the anal 
plates or valves, and (c) certain muscles that serve to admit of the withdrawal 
* TL. O. Howard and C. iy Marlatt. Op. cit., p. 44. 
_ + H. J. Webber, as the outcome of direct experiment, concludes that the “ insect diseases [of 
the orange] are apparently influenced by the use of fertilisers, organic manures rendering the 
trees more liable to injury from this source than ‘chemical fertilisers.”—Vid. Year-book of the 
U.S. Department of Agr. for 1894. Washington, 1895. : 
{ For an exact description of the forms of fungus life constituting ‘‘fumagine” in certain 
instances of its occurrence upon scale-infested plants, the reader is referred to D. McAlpine’s 
careful investigations recorded in a paper entitled ‘‘The Sooty Mould of Citrus Trees ; a Study 
in Polymorphism,” published in the ‘* Proceedings of the Linnean Society of New South Wales.” 
Op. cit., New Series, vol. xxi., pp. 469-499, pl. xxiii.-xxxiv. Sydney, 1897. . 
