490 GEOGRAPHICAL DISTRIBUTION OF INSECTS. 
in our cabinets a , we may very reasonably infer that at 
least three fourths of the existing species remain undis- 
covered. 
Certain groups and genera are found to contain many 
more species than others : for instance, the Coleoptera 
and Lepidoptera Orders than the Orthoptera and Neu~ 
roptera ,• the Rhincophora than the Xylophagi ,• the Dy- 
tiscidcE than the Gyrinidce ; Aphodius than Geotrupes ; 
Carabus than Calosoma. Again, some insects are much 
more prolific than others. Thus the Diptcra Order, 
though not half so numerous with respect to species 
as the Coleoptera, exceeds it greatly in the number 
of individuals, filling the air in every place and almost 
at every season with its dancing myriads. We rarely 
meet with a single individual of the most common spe- 
cies of Calosoma or Buprestis; whilst the formicary, the 
termitary, the vespiary, and the bee-hive send forth 
their thousands and tens of thousands ; and whole coun- 
tries are covered and devastated by the Aphides and the 
Locusts. An all-wise Providence has proportioned 
the numbers of each group and species to the work as- 
signed to them. And this is the view in which the nu- 
merical distribution of insects is most interesting and 
important : and we are indebted to Mr. W. S. MacLeay 
for calling the attention of Entomologists more particu- 
larly to this part of our present subject. 
With regard to their functions, insects may be pri- 
marily divided into those that feed upon animal matter 
and those that feed upon vegetable. At first you would 
be inclined to suppose that the latter must greatly ex- 
a Hor. Entomolog. 469. This calculation includes the Crustaeea. 
