Ch. XII.] USE OF COTTONY SECRETIONS, 229 



to keep it ; for the first ants that came up were only 

 pioneers, and by knocking these off it prevented them 

 from returning and scenting the trail to communicate 

 the intelligence to others. 



Before leaving this subject, I may remark that just as 

 in plants, some glands secrete honey that attracts insects, 

 others a resinous liquid that repels them, so the secre- 

 tions of different genera of the homopterous division of the 

 hemiptera are curiously modified for strikingly different 

 useful purposes. "We have seen that by many species of 

 plant-lice, scale-insects, and leaf-hoppers, a honey-like 

 fluid is secreted that attracts ants to attend upon them. 

 Other species of aphides (JEriosoma) that have no honey- 

 tubes, and many of the coccidae, secrete a white, flocculent, 

 waxy cotton, under which they lie concealed. In many 

 of the Homoptera, this secretion only amounts to a white 

 powder covering the body, as in some of the Fulgoridae. 

 In others it is more abundant, and it reaches its extreme 

 limit in a species of Phenax that I found at Santo 

 Domingo. The insect is about an inch in length, but the 

 waxy secretion forms a long thick tail of cotton-like 

 fibres, two inches in length, that gives the insect a most 

 curious appearance when flying. This flocculent mass is 

 so loosely connected with the body that it is difficult to 

 catch the insect without breaking the greater part of it 

 off". Mr. Bates has suggested that the large brittle 

 wings of the metallic Morphos may often save them from 

 being caught by birds, who are likely to seize some portion 

 of the wide expanse of wing, and this, breaking off, frees 

 the butterfly. Probably the long cumbersome tail of 

 the Phenax has a similar use. When flying, it is the 

 only portion of the insect seen ; and birds trying to cap- 



