408 SYSTEM OF INSECTS. 
pears to prevail most widely in nature is what may be 
called the quatemo-quinary ; according to which, groups 
consist of four minor ones ; one of which is excessively 
capacious in comparison of the other three, and is al- 
ways divisible into two; which gives Jive of the same 
degree, but of which, two have a greater affinity to each 
other than they have to the other three*. Mr. W. S. 
MacLeay, in the progress of his inquiries to ascertain 
the station of Scarabccas sacer, discovered that the thale- 
rophagous and saprophagous Petalocerous beetles re- 
solved themselves each into a circle containing^? such 
groups. And having got this principle, and finding that 
this number and its multiples prevailed much in nature, 
he next applied it to the Animal Kingdom in general : 
and from the result of this investigation, it appeared to 
him that it was nearly, if not altogether, universal 5 . 
Nearly at the same time a discovery almost parallel was 
made and recorded by three eminent Botanists, MM. 
Decandolle, Agardh, and Fries, with regard to some 
groups of the Vegetable Kingdom c ; and more recently 
Mr. Vigors thinks he has discovered the same qui- 
nary arrangement in various groups of birds d . This is 
least he has not built his system on this foundation, which appears 
an essential part of the quinary arrangement. (See Mr. W. S. Mac- 
Leay in Linn. Trans, xiv. 56 — .) As to value, the Papilionidce con- 
stitute the typical group or centre of the Order, though the Phala:- 
nidce prevail as to numbers : but neither of these are resolvable into 
two primary groups. 
a Linn. Trans, xiv. 56—. It is to be observed, however, that 
what Mr. MacLeay calls the aberrant groups are usually also resolv- 
able into two. '' Hor. Entomolog. 318, et 2)asshn. 
c Linn. Trans, ubi supr. Mr. W. S. MacLeay informs me that 
M. Agardh has found that the distribution of Fuci is regulated l>y 
the same law. d Zool. Journ. iii. 312—. 
