in the Tetramerous and Trimerous Coleoptera. 61 
since the number of joints in the tarsi of Coleoptera does not 
vary so much as has been supposed. This, it is true, is not an 
objection that will much affect the series of the Genera In- 
sectorum, so far as that work may relate to affinities, because it 
matters little whether insects are to be held together by being 
all pentamerous or all tetramerous ; but it most seriously affects 
the nomenclature of the tarsal system,— since, if I place a natural 
group with five joints to each of the tarsi among Tetramera, and 
another with four joints among the Trimera, I clearly give them 
a false description as well as an erroneous name. 
It requires little observation to perceive that Aristotle's group 
of Ptilota is typically pentamerous, or, in other words, that it 
has in its most normal forms five joints to the tarsus. Aberrant 
exceptions there are, however, to all rules of this kind ; and, as 
we have seen above, the arrangement of Coleoptera given by the 
French school of naturalists is grounded on such exceptions. 
Observations universally adopted as accurate, and judged of suf- 
ficient importance to form the basis of a system, are not likely © 
to be viewed with suspicion by young naturalists. While, 
therefore, on entering upon the science, I perceived that the 
tarsal system was at utter variance with natural affinities, I 
made no doubt of the statements upon which it was founded 
being in the main correct. It was certainly evident, as shown 
above, that this system, as propounded by the French entomolo- 
gists, would not contain all Coleoptera; and, on the other hand, 
that Illiger and Reichenbach had even exploded the section of 
Dimera; but no one carried his scepticism so far as to express 
. doubts of a Linnean Cerambyx and Curculio being different from 
a Carabus in being tetramerous, or of a Coccinella being properly — 
separated from a Chrysomela in being trimerous. The study of 
natural affinities, however, is of that admirable nature, that, 
while founded on observation, like a well-proportioned build- 
K 2 ing 
