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CHAP. XXI.] INSECTS. 501
sub-regions. Many of these, it is true, consist of single species
confined to a single island, and we will not lay any stress on
these ;
but there are also several important groups, which extend
over the Indo-Malay or the Austro-Malay islands only, stopping
abruptly at the dividing-line between them. For example, on
the Indo-Malay side we have Euryarthrum, Leprodcra, Aris-
tobia, Coelosterna, and Entelopes, and what is perhaps even more
satisfactory, the large genera Agelasta and Astathes, abundant in
all the Indo-Malay islands, but having only one or two species
just passing the boundary into Celebes. On the other side we have
Tethionea, Sphingnotus, Arrhenotus, Tmesisternus (the last three
genera abounding from New Guinea to Celebes, but totally
unknown further west), Hestima, Trigonoptera, AmUymmxi, Ste-
silea, Enes, and the large genus Micracautha, with but a single
species beyond the boundary,—30 Austro-Malayan genera in all,
each found in more than one island, but none of them extending
west of Celebes. Here we have clear proof that the boundary
line between the two great regions exists for Longicorns, as well
as for all other animals ; but in this case an unusually large
number have been able to get across it. This, however, does not
abolish the barrier, but only proves that it is not absolutely effect-
ual in all cases. Those Who maintain that the Malay Archi-
pelago forms a single Coleopterous region, must disprove or
explain the instances of limited range here adduced.
Out of nearly 1500 known genera of these insects, only one
genus, Clytns, appears to be cosmopolitan. Saperda and CalUchroma
aie the only others that perhaps occur in every region ; but
these are both wanting over wide tracts of the earth's surface,
Sap)erda being absent from Tropical Africa and the Malay Archi-
pelago ;
and Callichroma from the Australian region, except one
species in Polynesia. Many of the genera of Longicorns have a
somewhat wide and scattered distribution, indicative of decadence
or great antiquity. Mallodon and Parandra are mostly South
American, but have species in Australia and Africa ; Oeme is
found in Brazil and the United States, with one species in West
Africa ;
Ceratopliorus has 2 species in West Africa and 1 in New
Zealand. Xystrocera is mostly African, but has single species in