50 Dr. Jauzs MACBR1DE on the Power of 
The falling of thé insect as soon as it enters the tube is wholly 
attributable to the downward or inverted position of the hairs of 
the internal surface of the leaf. At the bottom of a tube, split 
open, the hairs are plainly discernible pointing downwards; and 
as the eye ranges upwards they become gradually shorter and at- 
tenuated, till at, or just below, the surface covered with the bait, 
they are no longer perceptible to the naked eye, nor to the most 
delicate touch. It is here that the fly cannot take a hold suffi- 
' ciently strong to support itself, but falls. The inability of insects 
to crawl up against the points of the hairs I have often tested in 
the most satisfactory manner. Spiders descend into the tubes, to 
prey (I suppose) on the entrapped insects, and ascend with impu- 
nity ; but this is performed, as.I have witnessed, by the assistance 
of their threads. Also a small species of Phalena* appears to take 
shelter in these tubes during the day, and is enabled to ascend ; 
but by what contrivance I am at a loss to conjecture; unless it 
be by some peculiarity of structure in its feet. E 
- In the putrid masses of insects thus collected, are always to be 
seen one or more maggots in a very active state. To account 
for their presence, and to ascertain the insect to which they be- 
longed, I was long unable. The mystery was however unveiled 
in the following manner: While watching attentively some tall 
tubes of the S. flava growing in their natural situations, in order 
to discover whether other insects as well as flies were attracted by 
the bait above described, a large fly caught my attention: it 
passed rapidly from one tube to another, delaying scarcely a mo- 
ment at the faux of each, until it found, as it should seem, one 
* This Phalena, which is about half an inch in length, may be deseribed by saying it 
is divided transversely into three equal parts; the first division including the head is 
black ; the second dirty white, or yellow ; the third is like the first: Larva a greenish geo- 
metra, 
suitable 
