, M. De la Hire feems to have been the .firft perfon who discovered
thefe Smooth eyes. He obferved three of them difpofed
in a triangular form, on the back part o f the heads of fome o f
thefe little creatures. He foon found that they were transparent,
and thence naturally judged them to be o f the fame
nature o f the cornea o f our eyes, and really to ferve the fame
office to the creature poffeffed of them.
We find three o f thefe fmooth eyes placed triangularly on the
back part o f the head o f vaft numbers o f the genera o f flies, as
well o f the two-winged as of the four-winged kinds; but there
are alfo fome o f both thefe claffes, in which they are wanting,
All the fpecies o f gnats, and o f tipulae, are without them. The
heads o f thefe are very Small in proportion to the bulk of their
body, and are in a manner covered by their reticular eyes. The
want o f the fmall eyes is amply made up by the fize and extent
o f the larger ; but there are fome other kinds which want them,
without having this advantage in their place. O f the two-winged
flies with Short bodies, the gad-flies want thefe eyes ; and amongv
the longer bodied and four-winged kinds, the flies produced from
the puceron-eaters (hemerobius);.
Notwithftanding, therefore, that many fpecies o f flies have
thefe eyes, there are yet fo many that want them, that Mr. De la
Hire would not have judged thefe to be their only eyes, if he had
made experiments on the reticulated ones, in the manner o f Meffi
Swammerdam arid Reaumur. Mr. Swammerdam put upon the
eyes o f certain flies a covering o f black, fteeped in o il; in this
flate they flew at random, and feemed to have no ftrength ; and
wherever they fettled they did not avoid the hand which would
!-' take
take them. M. Reaumur made alfo fome experiments upon the
reticulated eyes of bees, which were all taken from the fame
hive. He fpread upon them a covering of dark-coloured varnifh,
and fhut them up with fome of their companions which had not
been touched, in a large powder-box. At about eight or ten
fteps from the hive from whence they were taken, the cover of
the box was taken off; thofe which had their eyes clear immediately
took their flight, and went to their habitation; thofe
whole eyes were var-niflied made no hafte to- get out of the
box ; they had fome difficulty to determine themfelves for flight,
and the greateft number directed it at random, and on different
fides, and went not far. To oblige fome: o f them to fly farther,
they were thrown into the air; they raifed themfelves vertically
till they were loft, and not one of them feemed to know the way
to it’s hive.
T o know what would happen if the ftemmata were covered,
he put varnifh upon them, in the fame manner as was done to the
reticulated eyes, and let them likewife at liberty, about three or
four fteps from the hive ; not one feemed to know it’s way, or
even feek it. They flew on all fides upon the plants, but did not
fly far.
An infeft is, I believe, never found with both kinds o f eye3
but when it is in it’s perfeft ftate. The moth, for inftanee, which
hasfeveral thoufands o f eyes in the reticulated form, has only fix
fmall fmooth eyes in the ftate of the caterpillar. The wonderful
anatomiffi o f the coffus has fhewn, that the eyes of the latter are in
the form of a cup, and that the cornea, which is the cover- to this
cup, is very tranfparent. He has been enabled, to difcover a true
optic