113 
Genus Patrobus. 
ft 
vo specimens of P. longicornis, one from Central and the other 
I Southern Illinois, had eaten nearly twice as much vegetation 
fjhimal food. The latter consisted chiefly of caterpillars, and in- 
! 3d in fact nothing else but traces of plant-lice, eaten by one of 
two. A little of the vegetation was derived from grass, but the 
be of the remainder could not be satisfactorilv traced. 
THE FAMILY AS A UNIT. 
e have now to treat the various collections of Carabidae upon 
i li this paper is based, as distinct and unbroken groups, without 
ence to the genera of which they are composed. The eighty- 
3 specimens of all the species obtained in miscellaneous situa- 
are found to have derived forty-two per cent, of their food from 
inimal kingdom, while the seventy specimens captured in the 
ard so often mentioned, took seventy-seven per cent, of their 
from the same sources. The individuals from the cabbage field, 
Sver, show no such excess of animal food as those just men- 
d, the ratios standing for them at forty-one per cent. If we seek 
bcount for this striking surplus shown by the second group, we 
find, in the first place, a difference of more than sixteen per 
between the ratios of insects eaten by the first and second 
ps respectively,—a fact clearly due to the presence of canker- 
as where the second group wa's collected. This species was eaten 
ixteen of the seventy beetles, and composed about one-fiftli of 
contents of all the alimentary canals. This accounts, however, 
*nly about half the difference noted, the remainder appearing in 
arger ratios of other insects, of mollusks, of earth-worms, and 
idetermined animal food. 
is indicates either that other forms of animal life than the 
er-worms were superabundant in the orchard, or else that the 
ellaneous collections do not correctly represent the ordinary 
of the Carabidae. The truth probably lies between the two. 
extraordinary wetness of the season, together with the amount 
ibbish on the ground in the orchard, gave these beetles an 
ual opportunity to capture slugs and earth-worms, and 
ded excellent harborage for all sorts of insects. On the other 
, many of the beetles from other situations were preserved 
^ally for dissection because the circumstances of their capture 
,3 it seem probable that they were feeding upon vegetation. 
careful study of the data indicates one interesting and important 
with regard to the preferences of this family, namely, that wlieie 
straordinary abundance of any kind of animal food appeared, 
{ a consequent increase in the percentage of that kind appro¬ 
ved by the beetles, this increase was compensated, not by a 
jfase in the other animal elements, but in the ratios of vegeta- 
only,—a fact which clearly shows that the preferences of the 
i bidie are for animal food. It should be noticed, however, that 
irgument does not apply to all the genera, as is seen, for example, 
calling the record of Anisodactylus. The ten specimens of this 
3 taken in the orchard had eaten much more vegetation than 
lineteen from various other places. 
