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THE BRITISH NATURALIST. [N OVEMBER 



this case the mouth opening is distinctly under the third eye. It 

 may be that this rotatory organ is not a beard, for as the larva throws 

 its head back on the dorsal side constantly the eye may have 

 become developed in this abnormal position, as certainly it is just 

 where the creature would find its vision most needed to capture the 

 minute infusoria on which it feeds all the time the tuff is playing, 

 especially when one brings to mind the fact that in Gy.inus (the 

 whirligig beetle) there are four eyes, or rather the eyes on each side are 

 divided, two that look upwards towards the air to warn the insect 

 against its enemies from above, while the two lower ones peer down- 

 wards into the water on the look out for food. The eyes in the 

 larva of Dixa will therefore be somewhat unique if the protrusile 

 tuft is a "top-knot." 



We have recently been taking some very young forms of Sole and 

 Plaice in the estuary of the Ribble with a view to mount specimens 

 showing the gradual change in the position of their eyes ; for they leave 

 the egg with true bilateral eyes, but the one on the under or white side 

 gradually changes to the top of the head, and then moves slightly down 

 the upper or dark side to the final position so well known by everyone. 

 If, however, the rotatory organ in Dixa is a " top knot," then the eyes 

 must have been evolved in the lower lobe of the head to enable the 

 insect to capture its prey rather than to enable it to escape from its 

 enemies ; though this latter function would seem to be the main reason 

 for the special development of the eyes in most insects, especially when 

 fully matured. 



(To be continued.) 



THE SEXUAL DISTINCTION OF INSECTS. 



BY C. W. DALE. 



( Continued from page 240.) 

 IV. — Disparity of Antennae. 



Among the Butterflies, Sphinges, and Tortrices there is very little 

 difference between the antennae of the two sexes, but in certain species 

 of the Bombyces, Noctuae, Geometrae, and Tineae there is a great deal 

 of difference — those of the males being beautifully feathered, while 

 those of the females are plain. The best instance I know is that of 

 Ptilophora plumigera. Among the Bombyces the males of the 

 Bombycidae, Chelonidae, Saturnidae, Liparidae, Notodontidae, and 

 Zeuzera and Ino have feathered antennae. Those of the Lithosidae 

 and Euchelidae, Hepialus and Zygaena, have not. Among the Noctuae 

 are Heliophobus, Pachetra, Dasypolia, Gonoptera, Rusina, and Agrotis 



