l895-] ENTOMOLOGICAL NEWS. 99 



jected. The clusters of each side is connected by a rather massive trans- 

 verse cylinder of nerve- or brain-matter, an apparently unnecessary ar- 

 rangement — if the cluster or some of their respective eyelet would not 

 co-operate. Such a co-operation would certainly only exist between eye- 

 lets with parallel or convergent axes of vision and the clusters would be 

 very large and prominent, exhibiting parallel or convergent eyelets all 

 along the circumference of both the clusters. This is the condition of the 

 eyes in all fast moving insects as in Cicindela, Cistela, dipterous, neurop- 

 terous and lepidopterous insects in their imago state, and these insects 

 avoid collisions by deviating in a distance of several meters, while others, 

 as some Tenebrionidse and all those living in dark places or moving slowly 

 possess flat lateral clusters, often situated on the inferior surface of the 

 head. 



Probably the peripheral eyelets of the large clusters of fast moving 

 insects would be useful for perceiving distant objects and the eyelets 

 nearer the centre of the cluster, single or combined with its neighbor- 

 eyelet, but unable to receive the same rays as the opposite cluster for 

 near lateral objects only. 



The movements of the Cicindela indicate the use of the peripheral 

 eyelets for a clearer perception of objects. When approached sideways 

 they do not move as quickly away, but turn their front or back towards 

 the approaching object evidently for a clearer inspection. But there is 

 another habit to be considered: one can observe the Cicindela for quite 

 a length of time without alarming the insect, but as soon as you move its 

 motions signalize that you are seen. When they are in motion, or the 

 object is in motion, they evidently see quicker. When we look at the 

 sun or other brightly illuminated object and turn our eyes toward a dark 

 surface or close our eyes, we see a number of those bright objects which 

 appear even after we annihilate the images by opening our eyes and 

 closing them again; or, in other words, the retina retains for a certain 

 time the images received. If we admit the existence of the law of the 

 retinal retention of images in the arthropod as well as in the vertebrate 

 eye, the photographer may demonstrate the production of a continued 

 image in the eye clusters by the successive momentary exposure of a fast 

 moving animal to the photographic plates and the effect of the moving 

 series of pictures on our eyes when viewed through a small hole in a piece 

 of pasteboard. We see then only one image of the animal in lively 

 motion. When the image of a moving object falls successively on the 

 retinula of a row of eyelets, or when the insect is in motion exposing the 

 retina of a row of eyelets to the image of an object at rest the effect must 

 be the same. 



These are certainly all merely presumptions based on the physiological 

 actions of the vertebrate eye. but I do not see any reason to doubt that 

 the laws and facts of vision in the insect eye be based on different princi- 

 ples. The structure of the compound eye is so different, that one might 

 doubt whether insects see at all or see multiple images or only small parts 



