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an exception to the prevailing character of the Longicorn family, 
the elytra being excessively dilated — in fact, as near as possible 
hemispherical in shape, instead of elongated as is the almost 
universal rule. When I first met with it, I was deceived by its 
great resemblance to a common insect of the family Eumorphidee 
(Corynomalus discoideus) which swarms at times on the same de- 
caying branches of trees on which the Longicorn is found. It 
is true the size is much larger than that of the Corynomalus, but 
this is not noticed when they are in situ. The very curious 
black knob on the fourth antennal joint assists greatly to com- 
plete the disguise ; for this mimics the terminal club of the an- 
tennae of the Corynomalus ; and as the remaining joints in the 
Longicorn are very slender and imperceptible when the insect is 
on the tree, the organs in motion resemble precisely those of the 
Corynomalus. It is further remarkable that the Longicorn 
mimics especially a pale variety of Corynomalus discoideus, which 
is the prevailing form of the species at Ega. 
A second species of this genus is known from Cayenne, — the 
Cyclojjeplus cyaneus (Thoms. 1 . c.). I do not know whether this 
has its analogue in the same country, in a species of Coryno- 
malus. Both species are excessively rare. The Anisocerinae fur- 
nish many instances of adaptive mimetic resemblances; and to 
this peculiarity of the group is no doubt attributable the strange 
divergences or aberrations of form which it contains. In addi- 
tion to the clearer cases which I have noticed, there are others 
not quite so evident. For instance, I think our Hojjlistocerus is 
the mimetic analogue of a species of Stenochia, a Heteromerous 
genus, and the Acanthotritus dorsalis of South-east Brazil ap- 
pears to resemble much a species of Heilipus, belonging to the 
family Curculionidse. The Onychoceri, instead of mimicking 
other insects, have deceptive resemblances to the bark of trees 
on which they live. A tendency to mimetic resemblances seems 
to run in certain groups; and these groups are remarkable for 
the aberrations from their types in minor points of structure or 
in facies, and for the rarity and diversity of the specific forms 
which they contain. 
Subtribe Acanthocinit^. 
Group Layocheirince. 
Genus Lagocheirus (Dej. Cat.), Thomson. 
Thomson, Classif. des Cerambyc. p. 9. 
Body of large size, broad, oblong, slightly convex. Antennae 
stout, half as long again as the body, and of nearly equal length 
in both sexes; the sixth joint in the males having a tubercle 
