28 
entomologists should have so long 
neglected to give a more particular 
description of this little pest of our 
gardens; and, although your corres- 
pondent has very minutely traced the 
various transformations of this destruc- 
tive insect, yet, with your permission, 
Mr. Editor, I will say a word or two 
on the subject. 
From the letter of J. C. it seems he 
is not aware thet there are two kinds 
of larve, which are destructive to the 
foliage of the gooseberry bush; one of 
which is the production of the Pha- 
lena wavaria, or gooseberry moth, and 
is very correctly described in the quo- 
tation from Sturt’s Natural History ; 
the other is the Tenthredo rose, and 
which is more particularly the subject 
of your correspondent’s letter. These, 
it is plain, belong to two very different 
orders of insects; the former of which 
is of the order Lepidoptera, and the 
latter that of Hymenoptera. The cha- 
racter of the order Lepidoptera is,— 
Wings four, imbricated with minute 
scales. Generic character of the Pha- 
lena is,—Antenne taper from the 
base ; wings in general deflected when 
at rest: fly by night. The specific 
character of the Phalena wavaria is,— 
Wings grey: four black irregular 
stripes on the interior part of the 
upper wings; one resembling the Ict- 
ter L, 
The character of the order Hyme- 
noptera is,—Wings four, generally 
membranous: tails of the females 
armed with a sting. Generic charac- 
ter of the Tenthredo is,—Abdomen of 
equal thickness, and closely connect- 
ed to the thorax: sting serrated be- 
tween two valves; second wings 
shortest. The specific character of 
the Z'enthredo rosa is,—Antenne, head, 
and thorax black, with a yellow spot 
on each side of the latter; abdomen 
yellow; a black spot on the anterior 
margin of the wings. 
Though the larva of the P. wavaria 
enters the ground in order to change 
into a pupa, yet, from my own obser- 
vations of the various metamorphoses 
of the Tenthredo rose, 1 may inform 
J.C. that he is not correct in sup- 
posing that is the case with the cater- 
pillar of this very numerous and vora- 
cious little creature,—the aurelia of 
which is generally fixed to the dry 
‘stalk of some plant, the Jeaves, or 
small branches of shrubs or trees. 
Correct figures of both these inscets 
are giyen in Donayan’s. yaluable 
Mr. Doubleday on the Gooseberry. Caterpillar. 
[Aug. 1, 
work on the Natural History of Bri- 
tish insects, 
Besides the above, there is another 
moth which feeds on the gooseberry 
and currant bushes, called the magpie 
moth (Phalena grossulariata), the 
specific character of which is,— Wings 
whitish, with round black spots, and 
a yellow streak on the anterior part. 
This fly is very common in the months 
of July and August; and it is not a 
little singular, that this insect, when 
alarmed, will fall to the ground as if 
dead, and remain motionless till the 
appearance of danger is over. 
Epping ; E. DousvepDay. 
June 15, 1822. 
— 
Tothe Editor of the Monthly Magazine. 
SIR, 
NE of your readers is puzzled 
with the phenomena of the com- 
mon phial barometer. He asks,— 
1st. Why must the rim of the neck of 
the phial be separated before the wa- 
ter can be suspended? 2d. Why is 
the surface of the water concave in 
fine weather, and convex in rainy 
weather? 3dly. Why does the expo- 
sure of the phial to the heat of a fire 
produce the same effect as rainy 
weather? 
In answer to these questions I 
would say,—Ist. That it is not neces- 
sary to separate the rim of the neck 
in order to suspend the water. If the 
surface of the rim be perfectly even 
and dry, the water will be suspended 
just the same as when the rim is re- 
moved. The reason why itis neces- 
sary in any cases to strike off the 
rim, is because it is uneven, and will 
draw off the water, by making the 
surface heavier on one side than on 
another. 
2d. In fine weather the weight of 
the atmosphere is greater than in 
rainy weather, as is seen in the quick- 
silver barometer; in the former the 
column is about thirty-one inches, but 
in the latter about twenty-eight, 
When, by the collision of clouds of 
different degrees of humidity, rain is 
formed, the weight of the atmosphere, 
and consequently its density and its 
pressure on the surface of the water 
is diminished; the water therefore 
sinks, and a drop is formed. In fine 
weather the air remains charged with 
its humidity, and consequently its 
weight and density, and pressure on 
the surface of the water in the phial, 
are greater than in rainy weather ; 
hence 
