12 HOMOPTERA 



often svvarm over them in large numbers while feeding is in progress. Both nymphs and adults are 

 apparently oblivious of the presence of their hymenopterous companions, and continue their usual 

 activities with equal serenity whether ants are present or absent. 



The liquid sought by the ants has been much discussed in connection with the Aphida and the 

 Coccidte, and seems in no way different in the Membracida Itis colorless and transparent, rather heavy, 

 and somewhat sticky. When first exuded it is incHned to be frothy, due no doubt to bubbles of air 

 which emerge with it, but it quickly clears on settling. It is practically tasteless even in comparatively 

 large quantities, and many attempts to distinguish a sweet taste have proved unsuccessful. The term 

 H honeydew ii, therefore, commonly applied to the fluid, is hardly a descriptive one. It is very likely, 

 of course, that the liquid may contain sugars not detected by the human tongue, and this would seem 

 to be indicated by the fact that fermentation appears to begin if the substance is left exposed. No chem- 

 ical analysis of honeydew has been made by the writer. 



EXTERNAL ANATOMY 



The external anatomy of M embracidte dififers in rather interesting and curious, but more or less 

 superficial respects, from the other families of the Homoptera. This of course is due chiefly to the 

 unusual development of the pronotum and the adaptation of the other structures to conform to the 

 conditions thus produced. More fundamental are the types of wings and the arrangement of certain 

 sclerites which in some cases furnish good characters for classification. A brief summary of the more 

 important external structures is presented as follows : 



Exoskeleton. — The exoskeleton of the M embracidte \s siroT\g\y hvit not uniformly chitinized. 

 The head and thorax, particularly the latter, are hard to the point of brittleness; but in the abdomen 

 and in those parts of the meso- and metathorax that are covered by the pronotum, the impregnation 

 of chitin is much less heavy. 



The exposed parts of the cuticle — in the Membracida much of the actual body surface is not 

 exposed but is covered by the pronotal developments — are modified by remarkable and often grotesque 

 punctuations, ridges and areolations, the function of which is conjectural. The commonest decoration 

 consists of irregular arrangements of punctures, varying in size and distribution but fairly constant 

 in appearance. In fact, this punctuation, whether deep or light, fine or coarse, dense or scant, 

 has been used by practically all systematic workers on the group, and there can be no question 

 as to the taxonomic value of such structures at least as specific characters. These punctures are merely 

 depressions, or pits, extending into or even through the cuticle but in no case perforating the entire 

 body wall. They apparently have no connection with tracheal or glandular development and must be 

 regarded as being merely superficial sculpturing. Occasionally the pits give rise to hairs. This is, 

 however, of no significance so far as the association between the two structures is concerned, since in 

 the very pubescent species the hairs arise as abundantly from between the punctures as from theircen- 

 ters. Moreover, many strongly punctate forms are entirely without hairs, while many hairy forms are 

 entirely without punctures. The association of the two, therefore, is believed to be accidental. 



Pubescence of various types is common throughout the family. It varies from thick, tangled 

 mats to sparsely occurring thin liairs. Such growth occurs oftenest on the sides of the meso- and 

 metathorax and on the lateral areas of the pronotum. 



The colors of the exoskeleton are in the main somber and dull. As might be expected from 



