88 RHYNCHOPHORA. 
In the Bothrosterni a tibial prolongation is also evident, but it is split at the apex into 
two, and a third tooth is present at its base, the structure thus approximating to that 
found in the Hylesinides. 
In Chapuisia, a form of complex affinities, the tibial unguiculus is again evident: 
small on the hinder pairs, it is long and backwardly recurved on the front tibiz, and 
though really situate above the tarsal articulation, this fact may be overlooked in 
careless examination. The tibie of the Platypodides are readily homologized with 
those of Chapuisia; the unguiculus, prominent on the anterior pair only, may assume a 
position apparently on the lower side of the tarsal articulation. This is due toa 
twisting of the tibia and of its prolongation, which I take to be strictly the homo- . 
logue of the mucro of the Scolytides and Cossonide. The Platypodine, in which 
Chapuisia may be included, and which are easily separable by other equally important 
characters, are here removed from the position they usually occupy after the Tomicides 
tu the neighbourhood of the Scolyti, with which they present various points of 
affinity. 
No complete attempt has been made to define the differential characters between the 
Scolytide and the most nearly-allied genera of Cossonide (Rhyncolus, Stenoscelis, &c.). 
In many of the latter the development of the rostrum is as feeble as in the Scolytide, 
and the pygidium is not declivous. In Leconte and Horn’s ‘ Classification of the 
Rhynchophora of North America’ the pygidium is stated to be declivous in the 
Calandride (which include the Cossonide) and horizontal in the Scolytide, in which 
the terminal edge of the last ventral segment is acute and surrounds the last dorsal ; 
but to both rules there are exceptions. 
Nevertheless, the habitus of the Cossonide, the absence of elytral excavations or 
armature, and the rounded eyes will distinguish them without difficulty from such 
Scolytide as resemble them in tibial structure. Still it is noteworthy that even 
Chapuis has described an undoubted Cossonid, Onychius, among the Scolytide. 
The Central-American Scolytide fall into two subfamilies :— 
1. First tarsal joint (at least of the anterior pair) as long as the remaining joints 
united. 
Head not rostrate, not hidden by the prothorax; eyes rounded-oval, entire. 
Prothorax elongate, its flanks impressed before the base for the anterior 
legs. Anterior tibiz with a long curved unguiculus at the upper apical angle, 
their outer face carinate or scabrous. Middle and posterior tibiz shortly 
produced at upper apical angles. . . 2. 1. 1 1 ee ee ee ee) PLATYPODINA. 
2. First tarsal joint shorter than the remaining joints united. 
Eyes oblong, oblong-oval, emarginate, or bipartite, but not rounded. Pro- 
thoracic flanks sometimes impressed at the base for the anterior legs. An- 
terior tibize rarely carinate or scabrous on the outer face; when this is the 
case, they are not produced into an unguiculus at the upper apical angle . ScoLyTin#. 
