INVESTIGATION OF INSECTS. 557 
with regard to its economy and habits, as you may have 
had an opportunity of making.—As to foreign insects, 
wherever you can, upon good authority, be particular 
in indicating the country and station of each specimen. 
I need not say much to you concerning the micro- 
scopes you should use for the examination of insects, a 
common pocket one of three glasses of different powers 
will answer every ordinary purpose?. 
We have treated hitherto of insects as we find them 
now inhabiting our globe: but I must not conclude our 
correspondence without taking some notice of those that 
are found in a fosszl state. Fossil insects may be divided 
into those that are found in amber, and those that are 
found in ofher substances. 
It has been observed with respect to insectiferous am- 
ber, that the greater part of the insects found in it exist 
no longer in the countries that produce that amber, and 
that in every different locality the insects found in it are 
different. Thus the amber of Sicily contains various 
species of Coleoptera not to be met with in other ambers, 
while that of the Baltic is rich in Diptera and Neuroptera?. 
It is further observed, that the insects inclosed in the 
amber of Prussia, and those figured by Sendelius in his 
Historia Succinorum, all belong to genera at this time 
found in Europe‘. Insects of the following genera are 
recorded as having been found in this singular substance : 
Platypus, Elater, Atractocerus; Gryllus, Mantis; larvee 
2 For dissections the one recommended above, p. 194, may be used 
Sometimes a watchmaker’s eye-glass, which also sets the hands at 
liberty, will be found useful. ; 
’ N. Dict. d’ Hist. Nat. xxxii. 264. . ~ ded. xvi. 281. 
