Life History of Tetropiwm gabrieli. 203 
develop in the pupa they gradually recede, and, by the 
time the pupa throws off its skin, have been entirely drawn 
up into the abdomen and the tergite and sternite of the 
last segment closed over them. 
T found it very difficult to verify what was, for some 
time, conjecture, the parts in question being so delicate 
and liable, at the touch of a needle, to become dissipated ; 
but ultimately I succeeded in removing the loose skin from 
the pupa and exposing to view the underlying organs 
while yet they protruded a little. 
The f# pupa also bears vestiges of these tubercles (Plate 
XX, fig. 5), but they are so small as to be almost imper- 
ceptible, and are differently situated, nor have I had time 
or material at the last moment to ascertain exactly what 
part, if any, of the genitalia they become. 
A most interesting feature in the transformation to the 
pupal state is the manner in which the antennz assume 
their final position in the pupa. 
Immediately on the head and thorax being freed from 
the larval skin the antennze curl forward somewhat after 
the fashion of a ram’s horns, though not so much curled, 
When they are full grown the pupa revolves on the 
extremity of its abdomen first in one direction, and, with 
the help of the sides of the cell, rubs one antenna into its 
place behind the projecting femora ; then, revolving in the 
other direction, similarly arranges the other and _ rests 
(Plate XVIII, e, 7). 
VARIATION : (1) IN Stze.—This is marked. In accounting for 
it some have suggested that large and small races of this Tetropium 
exist locally. This is not the case. The condition of the tree governs 
the size of the generation subsisting in it. 
If it be of luxuriant growth at the time of felling, with a thick 
covering of juicy inner bark, and if ova should be deposited on it at 
the most favourable time, i.e. within a few months of being felled, 
and not too thickly, abnormally large larvee and pup will occur 
(Plate XVIII). 
Tf, on the other hand, the tree is small and the bark thin, and if 
the eges should be laid thickly; or if the bark has been previously 
partially exhausted by another generation ; or the tree felled so long 
that much of the sap has dried, the occupants will be small. 
A very healthy tree, lately felled and oviposited on soon 
afterwards, affords more favourable conditions of nutriment 
