53 
ochreous lunate spots behind the eyes. Elytra at the base dingy 
ochreous and granulated, each with two rounded spots, and the 
humeral callus black ; the rest of the surface is dark violet- 
brown, with four rows of angular spots, and the tip pale ochreous; 
the black spots in the same positions as in the type appear faintly 
through the violet-brown ground-colour. The rest as in the 
type. In this variety the pale spots of the elytra, already indi- 
cated in var. are strongly marked, and the ground-colour has 
become obscure. This change in the dress, added to the mark- 
ings of the head and the size and robustness of the whole body, 
give the variety an aspect totally different from the typical form. 
Taken sparingly at St. Paulo de Olivencia : all the individuals 
found were conformable to the description here given. 
This pretty insect seems very susceptible of local modification. 
The typical form is confined in its range to a very limited area 
around the town of Ega, on the Upper Amazons. It is there 
found in plenty on the trunks and branches of fallen trees in 
the virgin forest. At Fonte Boa, 120 miles above Ega, it occurs 
under a slightly modified local form {A. Fonteboensis), which 
would be scarcely worthy of remark were it not intermediate 
between the Ega type and the strangely transformed local variety 
or race, A. Olivencius, found at St. Paulo, 180 miles further west, 
or 300 miles in a straight line over a uniform country undivided 
by physical barriers from the home of its type. As before re- 
marked, when a species varies in this way from district to di- 
strict not far apart, it often happens that several closely allied 
but more distinct forms or species present themselves in districts 
further removed; these may be fairly suspected of being also 
modifications, considering the proof already obtained of the 
variability of the species. Several of these nearly allied forms 
occur in the present case. Thus I have no doubt, on perusing 
the excellent description, that the A. stellatus of Guerin-Mene- 
ville (Cat. Ins. Coleop. recueillis par Osculati, p. 27), found in 
Ecuador, probably on the banks of the Napo, is a further modi- 
fication of the A. Oncay in the direction of our var. Olivencius. 
There is also an undescribed species found at Cayenne [A. multi- 
guttatuSj Laferte,MS.)*, which diverges from A. Onca in another 
direction; and this may with great probability be referred to the 
same type. It is the custom of naturalists, when they subordi- 
nate varieties to a species, to fix upon one of the forms as the 
original, to which the rest are referred : this original is generally 
the one first described or best known. In accordance with this 
usage, I have said that such and such forms are varieties of A. 
Onca ; but, strictly speaking, no form can be said to be a variety 
* I regret being unable, not having a specimen at command, to give a 
description of this species. 
