478 GEOGRAPHICAL DISTRIBUTION OF INSECTS. 
in our cabinets*, 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 Latr. than the Xylophagi Latr.; 
the Dytiscide than the Gyrinide ; Aphodius than Geo- 
trupes ; Carabus than Calosoma. Again, some imsects 
are much more prolific than others. Thus the Diptera 
Order, though not half so numerous with respect to spe- 
cies 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 ProvripEeNncE 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 anzmal matter 
and those that feed upon vegetable. At first you would 
be inclined to suppose that the /atter must greatly ex- 
? Hor, Eintomolog. 469. This calculation includes the Crustaeea. 
