458 Retrospective Criticism. 
“ Three aeronautic spiders ascended from the same spot, when each moved 
in a different direction,” &c. (p. 81.) Now, that no collusion may be sus- 
pected in the case, it may suffice to mention, I have not the honour to 
know Mr. Thompson personally, and have had no communication whatever 
with him; nor is it likely he had seen my work on aerial electricity. This 
was published i in December last, and Mr. Thompson’s communication has, 
for the first time, appeared in the present Number (Jan.). How long it has 
been in your possession I know not, but of its existence I at any rate was 
ignorant. It is palpably evident that in the one case the projectile thread 
was independent of a current of air. The naturalist of Selbourne declares 
the same thing, and he was a keen and cautious observer; and it seems 
also clear that in both the floatage owned another cause than the ascent of 
calorific emanations. I have, however, other facts, which I shall elsewhere 
adduce, and that I believe will set the matter to rest. — J. Murray. Car- 
mar then, April 2. 1830, 
Nidus on a Rush. — Sir, The nidus figured in Vol. IT. p. 104. is not, I 
believe, the work of an aquatic spider, as supposed by your correspond- 
ent, and also by our celebrated entomologist, the Rev. W. Kirby (Vol. IL. 
p 405.), nor is it so uncommon as it is considered by that indefatigable 
and successful collector, Captain Blomer, (Vol. I. p. 303.) TI have found 
it on high stalks of grass in shallow road-side draims, which are dry in 
summer and at other times when water does not abound: this shows that 
it is not the nest of an aquatic spider. I have to mention another circum~ 
stance respecting it, which seems to have escaped the notice of others, and 
which will account for its supposed rarity. This snow-white silken fabric 
is concealed by a covering of mud soon after itis spun. Several years ago, 
when I was on an entomological ramble in the neighbourhood of Stowey, 
in Somersetshire, I found a few of the nests, just like those figured. On 
searching further, [ met with one partly covered with mud, which led me to 
the discovery of others thoroughly plastered over. In this state they resem- 
bled bits of dirt splashed from the road on the stalks of grass. The plaster 
was evidently collected by the parent spider from the moist bed of the 
drain from which the grass 
grew. I could have collected 
dozens of the nests in the dif- 
ferent states: the plastered 
ones were the most numerous. 
I brought home a few, but the 
young spiders s never came out, 
and I regret that I cannot in- 
form you wnat species perform 
this ingenious work, for | con- 
sider it as beautiful and in- 
teresting as any thing recorded 
in the history of insect architecture. I have reared young spiders from 
analogous nests, a sketch of which I send herewith, together with figures 
of our beautiful nidus in its unplastered and plaster aa state. (jig. 113. )— 
—W. B.B.W. February 20. 1830. 
The Hessian Fly.— The insect figured by Mr. Kirby (Vol. I. p. 227.) is 
evidently one of the Culices; but he refers it to the Tipula genus. 
The T'ipule, I believe, are destitute of a trunk, with which the Ciilices are 
furnished. The resemblance of some of the smaller species of these two 
genera is so close, that they have been confounded by both Goedart and 
Swammerdam. — A. L. A. Alnwick, April 7. 1830, 
Flys Eye under the Microscope. —By far the most beautiful phenomenon 
of this kind is exhibited in the picture of the window reflected from the 
numerous facets of the compound eye of the Libéllula or dragon fly, and 
this multiplied image becomes extremely curious, being in motion, when an 
113 
