THE APHIDES OF GUERNSEY. 



BY MR. W. A. LUFF, F.E.S. 



The Aphides are popularly known as green flj or plant lice. 

 They belong to the Homoptera^ a sub-order of the Hemiptera. 



Everybody is familiar with their general appearance as 

 they are found infesting the flowers and plants in our gardens 

 and greenhouses. There is, in fact, hardly a fruit or forest 

 tree or cultivated plant which is not attacked by one or more 

 kinds. 



They are small, soft insects, the head has long and thread- 

 like antennae and is furnished with a beak, which is often half 

 as long as the body, sometimes quite as long, or longer. 

 By this beak or rostrum the juices of the plant are drawn 

 into the mouth by a sort of alternating or pumping motion. 

 The abdomen usually bears on its upper part near the end 

 a pair of tubercles, called cornicles, long or short ac- 

 cording to the species. These are hollow tubes and their 

 use is not well known. Some writers have thought them 

 to be connected with the breathing apparatus, but our 

 greatest British authority, Mr. G. B. Buckton, says " The 

 cornicles must be regarded as the external termina- 

 tion of excretory ducts, which do not permit the regur- 

 gitation or recession of air into the body of the Aphis." 

 The larvas are very similar to their parents, only they are 

 without wings. In the pupal stage they have the rudiments 

 of wings, and when fully developed there are winged males 

 and winged and wingless females. In some species the males 

 have not yet been observed. In some cases, as with the 

 Phylloxera of the vine, there are distinct forms of the same 

 species that live underground on the roots and above on the 

 leaves and shoots. One species, Chaitophorus aceru^ which is 

 common in Guernsey, has a remarkable dimorphous form 

 which has excited much interest amongst biologists on account 

 of its bearing on the question of the Origin and Variation of 

 Species. This form varies so much from the normal insect 

 that comparatively recent authors have placed it under a 



