JuLY 21, 1899. ] 
been there six months knew all about the 
weather, but one who had been there six years 
never knew anything about it. A similar para- 
dox is common in biological science ; and hence 
it results that Mr. Marlatt, who has only re- 
cently begun the study of Coccidee in detail, is 
much more sure about the nature of their spe- 
cific characters than the present writer, who 
has been occupied with these insects for eight 
years. If there is one thing which the detailed 
study of species teaches, it is that no man can 
prophesy beforehand what characters are going to 
prove specific and what variable. When the 
material available is scanty it is largely a mat- 
ter of guess work to pick out the specific char- 
acters, and the majority of new species pro- 
posed must be regarded in a sense as provis- 
ional. Indeed, the conditions for the absolute 
proof of the validity of a species are rarely ful- 
filled, since it has to be demonstrated that no- 
where in its whole range does the alleged species 
intergrade with any other. Let the ornitholo- 
gist of the Middle States, familiar with the 
yellow-shafted Colaptes, go to the Far West and 
find there the red-shafted species, C. cafer. In 
either locality he may examine thousands of 
birds, yet the differences are quite constant ; 
the species are indubitably ‘good.’ But now 
let him go to eastern Wyoming, and he finds 
the two inextricably mixed up, and concludes 
that there is only one Colaptes from the Atlantic 
to the Pacific. 
The general statements made by Mr. Marlatt 
are most of them applicable to the majority of 
Coccidz, and so far are neither new to nor un- 
heeded by the authors of the work he criticises. 
But there are exceptions, more numerous, 
probably, than most of usimagine. Take the 
often quoted case of the Jamaican <Aspidiotus 
aurantit, which attacks palms and lignum vite, 
but never Citrus. This creature is indistin- 
guishable, so far as known, from the pest of the 
orange tree found in California and elsewhere. 
Mr. Marlatt cannot fail to see that a distinction 
of this sort, however troublesome to the system- 
atist, is both of scientific and economic impor- 
tance. But this form of A. awrantii has not yet 
been proposed as a species, in the ordinary 
sense of the word, nor has it even any name. 
Some varietal names have been proposed by 
SCIENCE. 87 
Maskell and King for a few Diaspinz which 
burrowed under the epidermis of plants, and 
this fact is thus distorted by Mr. Marlatt: 
“Several species, or subspecies, of scale insects 
have been established on accidental variations 
of this character, as, for example, Chionaspis 
furfurus, var. fulvus, King. Examples of the 
types of this species, * * * ete.” It really looks 
as if the writer of the paragraph considered 
variety, subspecies and species to be synonymous 
terms ! 
What has really happened is this: In the 
course of years past, one after another, new 
forms of Aspidiotus came to the hands of stu- 
dents of Coccide. These were examined and, 
when apparently distinct from others, were 
described and named, sometimes as species, 
sometimes as varieties. Some little time ago 
Mr. Marlatt proposed to make a critical study 
of Aspidiotus, based on the valuable collections 
of the Department of Agriculture and such 
other material as could be obtained. Those 
.who had described new species mostly sent 
their types or co-types, and thus Mr. Marlatt 
had before him a much better series than any 
other student, few of the valid species being 
lacking. The present writer has had the pleas- 
ure of going over Mr. Marlatt’s work, and 
gladly testifies that it is excellent and will, 
when completed, mark a great advance in our 
knowledge of the genera examined. As might 
be expected under the circumstances, Mr. Mar- 
latt has detected various errors in the work of 
his predecessors, and in other cases believes, 
but cannot prove, that their conclusions are 
wrong. Several species are to be reduced to 
varieties or synonyms ; some varieties are to be 
raised to species. For all of this let us be sin- 
cerely thankful, but it is not an occasion for 
running amuck. The present writer never sat 
down to any lengthy piece of work without 
finding many things to be changed in his own 
former results and those of others. It is quite 
useless to hope to avoid error, but by continu- 
ous study we may gradually approach nearer 
and nearer to truth. That is all I ever hope to 
do or expect of others. 
‘The writer trusts that the foregoing criti- 
cisms will be taken in the kindest spirit, as 
they are intended, and he does not wish it 
