NOTES ON THE WHIRLIGIG BEETLE. 67 
curiously modified limbs. Prof. Miall states* that Gyrinus is 
unable to fly from the surface of the water direct, but must 
needs first climb the stem of a plant. I think I am correct in 
stating that the sensory organs of most insects lie in the antenna, 
but Gyrinus depends not alone on these for the detection of its 
sustenance ;{ eyesight here plays no small part. The compound 
eyes of the Whirligig are well known to those who are acquainted 
with these insects, but I may be here allowed, for the benefit of 
the uninitiated, to briefly dwell upon their peculiarities. They 
consist of two separate portions interposed by the socket of the 
antenns. Some writers have thought that the facets of one 
portion are for vision alone, and the other portion for vision 
below the water. Referring to this, Prof. Miall sayst :—‘ I once 
endeavoured to determine by direct observation whether the 
lower patch is actually submerged or not, but found that the 
capillary curves above the head and body render it very difficult 
to decide where the water-line curves. These curves must 
greatly obscure, or at least limit, vision by the lower lenses.”’ 
The large Water-beetle (Dytiscus marginalis), I have found, 
depends—at any rate, to very great extent—on its antenne for 
food. A captive Dytiscus, when at rest, took no notice of small 
pieces of raw meat dropped just in front of it, but not close 
enough to come in actual touch with the antenne ; but a piece 
of meat held between forceps and gently lowered into the water, 
and made to come in contact with the antenne, was at once 
seized. On one occasion I threw a dead fly on to the surface of 
the water in a vessel containing some captive Whirligigs. At 
once two or three of the beetles clustered round it, and, after 
toying with it for a moment, left it. Here sight must have been 
the leading factor that drew them to the fly. 
It may not be out of place here to say a few words about the 
sense of fear in insects. Thisis rather a complex subject which 
others more qualified than myself are better able to study, so I 
will but briefly touch upon it. In the full meaning of the word, 
as the higher animals know it, insects have no fear, or, if they 
* * Aquatic Insects.’ 
+ I have here purposely not made use of the word “ prey,” for, as far as 
my own observations go, Gyrinus is a scavenger. 
Gee 
{ ‘ Aquatic Insects.’ 
