350 The American Naturalist. [April, 
tropical region. Dr. LeConte, writing thirty-seven years ago, speaks 
of it as a “ sub-tropical province.” 
Looking through the list of species belonging to the five families 
treated in the present portion of this report, it seems to the writer that 
no one familiar with the Coleopterous fauna of the United States can 
pick out more than five or six which can be called characteristic of the 
Lower Sonoran zone, though it is true that quite a number range into 
it. A number—perhaps fifteen or sixteen—are tolerably characteristic 
of the Upper Sonoran, while possibly twelve or fourteen are more par- 
ticularly tropical. The great majority are species of very wide distri- 
bution in eastern and central North America, many of them extending 
even to the Canadian boundary. No doubt can be entertained, however, 
that a study of the phytophagous families will yield a larger percentage 
of Sonoran and tropical species, since we may naturally infer that the 
carnivorous beetles, of which the present list is mainly composed, are 
less affected by peculiarities in the flora than the phytophaga. 
More will be said on the subject in the concluding number of this 
article. For the present it will be sufficient to state the conviction that 
there is even less ground for considering the Brownsville beetle-faunas 
as Lower Sonoran than for classing it as tropical. The little jungles 
noted by Mr. Schwarz are to be considered, it seems, almost truly 
tropical, while, ou the other hand, there are large areas of a very dif- 
ferent nature surrounding these little forests, with a totally different 
Coleopterous contingent. Some of these areas are, from their elevated 
situation and dry climate, almost typically arid Lower Sonoran, while 
the low-lying damp spots, not tropical, will show a high percentage of 
forms common in humid regions occupied by what Dr. Merriam has 
called the Carolinian and Austroriparian faunas. In other words. 
Brownsville and its environs are not in one life zone, but in at least 
two, and probably three, the limits of these zones being locally irregu- 
lar, and determined not by temperature conditions, but by those of soil 
and humidity, which, through their action on plant life, also influence 
the insects. The only way in which these conditions could be approxi- _ 
mately indicated on a map, would be by spotting it with appropriate 
colors as in mapping Boreal or Arctic faunz on isolated mountain 
peaks. 
Life-history of Xylina.—In Bulletin 123 of the Cornell Uni- 
versity Experiment Station, Mr. M. V. Slingerland discusses at length 
the life-history of three species of Xylina—antennata, laticinerea, grotet 
—which have done considerable damage by eating holes in young 
