100 THE CANADIAN ENTOMOLOGIST, 



alence of the notion that the Aphides eject the honey-dew through the 

 cornicles; Kyber, Kaltenbach, Forel and others, who held to the views of 

 Bonnet. 



It can, however, be easily ascertained that the honey-dew is excreted 

 exclusively through the anus and never by the cornicles. When an ant 

 strokes an Aphis with its antennas, a clear drop appears, always at the end 

 of the abdomen, whilst the cornicles excrete nothing. On the other 

 hand, if an Aphis be picked up in the fingers, or if it be touched with a 

 straw, a tiny drop at once appears at one or both cornicles, which is 

 always coloured. 



Certain authors have held that these appendages formed part of the 

 respiratory system, a theory clearly erronerous. Witlaczil has even 

 thought that they appertained to the urinary system, but, on the one hand, 

 the product of the basal glands of the cornicles does not show any of the 

 uric acid reactions ; and, on the other hand, Kowalevsky has demon- 

 strated that in the Aphides the end of the intestine is functional as an 

 urinary organ in the absence of the Malpighian tubes. Professor Knor's 

 analysis, published by Biisgen, proved that the viscous liquid excreted 

 through the cornicles is a waxy substance. 



" In order to understand the object of this waxy matter, one should 

 observe a colony of living Aphides. Ii can then be seen that the colony 

 rids itself of its excreta through the anus in the form of clear drops, 

 especially when they are stroked by their friends the ants ; during this 

 operation their cornicles are quiescent and inactive and show no change. 

 But if an aphidophagus insect, particularly a Coccinellid or the larva of a 

 Chrysopa, approaches a plant louse, the latter puts out at the tip of one or 

 the other cornicle a tiny viscous drop, aims the cornicle towards its enemy 

 and endeavours to apply the drop to the head, the jaws or the thorax. If 

 this manoeuvre is successful, the enemy retires at once and does all it can 

 to rid itself of the adherent drop, which dries at once, and which is ap- 

 parently extremely disagreeable to it." Hence Dr. Horvath defines the 

 cornicles thus : 



" The cornicles of the Aphides are the excretory canals of wax-pro- 

 ducing glands differentiated in a special manner, and the product of which 

 is a means of defence against the Coccinellidse and the Chrysopidse." 



Those unfurnished with cornicles do not need this protection, since 

 some live underground and others are covered with a waxy secretion. 

 There are few Aphides unprovided with either of these means of defence. 



