SEPTEMBER 10, 1897. ] 
become degenerate through age and cannot 
successfully resist competition with the 
more vigorous forms introduced from the 
younger continent of Europe,* and that there 
are not-yet-formulated climatic differences 
favorable to the development of Palearctic 
forms on the American continent ; but these 
theories seem insusceptible of proof, and 
for the present we must content ourselves 
to accept the facts as we find them. 
The insects which are accidentally im- 
ported are carried in three main ways. 
Hither (1) they are unnoticed or ignored 
passengers on or in their natural food, 
which is itself a subject of importation, such 
as nursery stock, plants, fresh or dried fruit, 
dried food stuffs, cloths, lumber or domes- 
tic animals; or (2) their food being the 
packing substances used to surround mer- 
chandise or the wood from which cases are 
made, they are thus brought over; or (3) 
they may be still more accidental passen- 
gers, having entered a vessel being loaded 
during the summer season, and hidden 
themselves away in some erevice. The 
coleopterists (Hamilton and Fauvel) make 
a distinction by name among these classes, 
calling the first group ‘ insects of commerce ’ 
and the latter ‘ accidental importations.’ 
It would appear on the face that these 
more strictly accidental importations must 
be rarer than those which are termed com- 
mercial importations, yet of the 156 intro- 
duced Coleoptera recorded by Dr. Hamilton 
in 1889, sixty only were considered by that 
writer as insects of commerce, while 96 he 
thought had been brought over in this 
accidental way. 
The remaining Coleoptera common to 
North America and the Palearctic region, 
278 in all, Dr. Hamilton considers to be 
practically cireumpolar species, or at least 
not imported. Fauvel in his remarks and 
* The spread of European species in Australia has 
been explained by the superior energy of the younger 
races of the Palearctic region. 
SCIENCE. 
389 
additions to Hamilton’s catalogue raises 
the number of non-introduced or circum- 
polar species to 366, leaving 125 as im- 
ported, of which only 28 appear to have 
been imported from temperate Europe, the 
rest being cosmopolites or subcosmopolites. 
Of the latter class he thinks that 59 origi- 
nally came from the temperate Huropeo- 
Siberian fauna, 10 from the Oriental fauna, 
15 from the Ethiopian, 4 from the Neo- 
tropical, 7 being uncertain and 2 unknown.* 
It should be noted, however, that there 
is grave room for difference of opinion re- 
garding a number of the European species 
considered by him as indigenous to North 
America. Scolytus rugulosus, Hylastinus tri- 
fol, Anthrenus scrophularice, Sitones hispidu- 
lus, Cryptorhynchus lapathi, and a number of 
others which might be specified, have un- 
doubtedly been imported from Europe and 
were quite possibly originally imported. 
There are obstacles in the way of the 
establishment and spread of species which 
are imported quite by accident which usual- 
ly do not exist in the case of the so-called 
commercial importations. In many cases, 
entering the vessel by accident, they exist 
there as single individuals, and upon libera- 
tion, even should the conditions be favor- 
able, only gravid females could perpetuate 
the species. Then also the majority of 
such specimens are liberated, upon the un- 
loading of the vessel, upon the wharves. 
The water front of a seaport city is not a 
favorable place for the establishment of a 
species which feeds on living vegetation. 
Frequently, even when it is a species well 
fitted for acclimatization, it will have to fly 
or be carried for miles inland before it can 
find a place possible for the establishment 
of the species. So it happens that while 
foreign insects are frequently found in liv- 
ing condition about the wharves of our 
* Hamilton, in his 1894 paper, raises the number 
of Coleoptera common to the two countries to 594, 
making the number of introduced species 216. 
