Life History of Tetropium gabrieli. 209 
space in the middle of the tube with wads of tissue paper. 
If the groove was not made too deep for the larva it 
would follow it in its excavations readily, feeding along it, 
and thus be kept in sight. If made too deep the larva 
buried itself in the bark. 
The tube must not be with a neck and metal cap such 
as those used by Mr. G. Smith in rearing Criocephalus and 
_Asemum in their advanced stages (Plate XIX, ¢, /), for the 
neck being narrower than the body does not admit of the 
cylinder of bark being inserted close enough to the glass 
to keep the minute larva in the groove, and is in other 
respects impracticable. 
This corked glass tube method was fairly successful, 
and by it I brought larve through their first moult with 
considerable trouble. But the chief objection to it was 
the difficulty of removing the ring of bark from the tube, 
when changing the larva, without rubbing the latter 
against the glass and crushing it. 
No. 2.—Having thus lost several larvze, I devised the 
better plan of 2-in. squares of flat glass laid on to the 
inner surface of bark taken entire from the log and bound 
tightly to it with string, the larva, as before, being inserted 
between (Plate XVII). This answered admirably. 
Care, of course, must be taken (1) that too much 
moisture does not condense on the glass and drown the 
minute larva, and (2) that the bark is changed, at least, 
every third day to avoid mildew. 
Under the lens I have observed newly-hatched larvee 
consume the threadlets of freshly-formed mildew when 
excavating against the glass, but if they do so to any 
extent they become unhealthy and die. 
It is well to place the pieces of bark containing the 
larvee in a tin out of doors, covered over with a damp cloth 
to ensure their not drying up entirely. They must be 
kept from the direct rays of the sun and from the rain, 
but be given all the ventilation possible. 
In the late autumn, if it is desired to force them indoors, 
it is a good and simple plan to place them on a mantelpiece 
over the warmest fire-place accessible in a tin with a few 
holes in the lid to admit of a little ventilation and at the 
same time to retain sufficient moisture in the pieces of bark. 
They do best in a temperature of 80°-90° Fahr. A hothouse 
would probably answer the purpose as well. Prior to 
adopting these two methods of rearing the young larva 
