Life History of Tetropium gabrielt. 211 
I had, at times, as many as four dozen tubes occupied, and 
have reared as many as five imagos in one tube at the 
same time. 
The tubes were placed over a fire-place in a temperature 
of 76°-90° Fahr. In this temperature development was 
rapid, the pupal state only lasting seven or eight days in 
some instances. 
The cork should fit close down on the top of the wood 
to prevent the larvee wandering and invading each other’s 
cells. A very small groove may be cut down the side of 
the cork with a penknife, communicating with each larva 
to admit of ventilation and the escape of excessive 
moisture. 
Should too great moisture condense on the glass in the 
cells the cork must be removed for a while. The reason 
for using wood instead of bark for the final stages of the 
insect is that it is less liable to become mildewed. 
Mildew renders it almost impossible to bring a full-fed 
larva through to a healthy imago in tubes or bottles of 
bark, unless the larva be allowed to bury itself entirely in 
a thick piece and wad itself in, in which case, of course, it 
cannot be observed. 
After rearing one feeble beetle in bark in a metal-capped 
tube, inserted when pupating (Plate XIX, ¢, 7), I renounced 
the plan and used cylinders of wood with great success. 
Nor is it possible to bring them through healthily in 
bark by the flat glass method (No. 2) used for feeding up 
the larvee. Wood is, in all cases, the safest after the larva 
is full fed. 
No. 4.—Where turned wood-cylinders for the tubes are 
not procurable another method has suggested itself to me 
which answers well. It consists in substituting wood for 
bark in method No. 2. Small blocks of wood, about 2 in. 
square, by 1 in., must be cut with even surface, and pieces 
of glass to fit them (Plate XVIII, a, b,c, d). Insert the 
larva or pupa in grooves cut on the surface of the wood 
with 4-in. gouge (Plate X VIII, a), then apply the piece of 
glass and bind tight with string. Stand the pieces up on 
end so that the grooves lie perpendicularly with the 
openings above and do as in No. 2. In this case, as there 
is no cork to contain the larva in the groove when first 
inserted, put in a small stopper of cotton wool. 
I know of no other method by which the excavations of 
the larva in the wood, the establishment in the pupa-cell, 
