_, states that the inhabitants of Lombok use the large
species for food, and catch them by means of limed twigs.

They are distributed over the whole world excepting the polar regions,
but are especially insects of the tropics. At the present day about 2200
species are known, dispersed unequally among the several subfamilies as
follows: Agrionina, 700 species; Calopterygina, 280; Gomphina, 320;
Aeschnina, 170; Corduliina, 130; Libellulina, 600. In Europe proper only
100 species have been observed, and about 46 of these occur in the
British islands. New Zealand is excessively poor, and can only number 8
species, whereas they are very numerous in Australia. Some species are
often seen at sea, far from land, in calm weather, in troops which are
no doubt migratory; the common _Libellula quadrimaculata_, which
inhabits the cold and temperate regions of the northern hemisphere, has
been frequently seen in immense migratory swarms. One species (_Pantala
flavescens_) has about the widest range of any insect, occurring in the
Old World from Kamtchatka to Australia, and in the New from the Southern
States to Chili, also all over Africa and the Pacific islands, but is
not found in Europe. The largest species occur in the _Aeschnina_ and
_Agrionina_; a member of the former subfamily from Borneo expands to
nearly 6-1/2 in., and with a moderately strong body and powerful form; in
the latter the Central American and Brazilian _Megaloprepus caerulatus_
and species of _Mecistogaster_ are very large, the former expanding to
nearly 7 in., and the latter to nearly as much, but the abdomen is not
thicker than an ordinary grass-stem and of extreme length (fully 5 in.
in _Mecistogaster_).

_Fossils._--Among fossil insects dragon-flies hold a conspicuous
position. Not only do they belong to what appears to have been a very
ancient type, but in addition, the large wings and strong dense
reticulation are extremely favourable for preservation in a fossil
condition, and in many cases all the intricate details can be as readily
followed as in a recent example. From the Carboniferous strata of
Commentry, France, C. Brongniart has described several genera of
gigantic insects allied to dragon-flies, but with less specialized
thoracic segments and simpler wing-neuration. These form a special
group--the Protodonata. True _Odonata_ referable to the existing
families are plentiful in Mesozoic formations; in England they have been
found more especially in