SIR JOHH LUBBOCK OH AUTS, BEES, AHD WASPS. 125 
Oh the Ftthctioh of the Compoehd Eyes ahd Ocelli. 
Eorel agrees with Eeaumur, Marcel de Serres, and Duges, that 
in insects which possess both ocelli and compound eyes the 
ocelli may he covered over without materially affecting the move- 
ments of the animals ; while, on the contrary, if the compound 
eyes are so treated, they behave just as in the dark. Eor instance 
Eorel varnished over the compound eyes of some flies ( Calli - 
plioria vomitoria and Lucilia ccesar ), and found that if placed on 
the ground they made no attempt to rise, while if thrown in the 
air they flew first in one direction and then in auother, striking 
against any object that came in their way, and being apparently 
quite unable to guide themselves. They flew repeatedly against 
a wall, falling to the ground and unable to alight against it as 
they do so cleverly when they have their eyes to guide them. 
Finally, they ended in ftying away straight up into the air and 
quite out of sight. 
Johannes Muller inclined to the opiuion that insects saw near 
objects with their ocelli. Plateau satisfied himself that the move- 
ments of insects are not affected by the ocelli being covered over, 
and hence concluded that they are rudimentary organs. The com- 
plexity of their structure, however, seems fatal to this conclusion. 
Forel confesses that the use of the ocelli still remains an 
enigma, but he is disposed to think that they enable their 
possessors to see in comparative darkness. He observes * that 
they are specially developed in insects which require to see both 
in bright light and also in comparative obscurity. Aerial insects 
do not generally require or possess ocelli. 
Lebert expresses the opinion f that in spiders some of their 
eight eyes — those which are most convex and brightly coloured — 
serve to see during daylight ; the others, flatter and colourless, 
during the dusk. Pavesi has observed J that, while the species 
of Nesticus possess normally eight eyes, in a cave-dwelling species 
(. Nesticus speluncctrum ) there are four only, the four middle eyes 
being atrophied. This suggests that the four central eyes serve 
specially in daylight. 
Sehse of Smell. 
In my previous memoirs I have recorded a few experiments 
which convinced me that ants are gifted with a very highly 
developed sense of smell, and that this resides in the antenme. 
* L. c. p, 181. t Die Spinnen der Schweiz, p. 6. 
f “ Sopra una nuova specie di Kagni appartenente alle collezioni del Museo 
Civico di Genova,” Ann. Mus. Civ. 1873, p. 344. 
