1921] Wheeler: Some Social Beetles 59 



knife-blade. But all the uninjured soon return to the two half- 

 cavities and remain in them. At first I carefully kept the tubes 

 in the dark, but I soon found that they could be left in the 

 diffuse day-light on my table without disturbing the activities 

 of the insects. It was necessary, however, to keep them in a 

 horizontal position, like that of the petiole on the living, plant, 

 for when they were placed upright, gravity seriously interfered 

 with the activities of the beetles and especially of the larvae, 

 causing them to drop and accumulate at the lower ends of the 

 cavities or of the tubes. Of course, this position did not inter- 

 fere with the coccids which remained attached by their sucking 

 mouthparts to the nutritive parenchyma. Colonies of Coccido- 

 trophus can be kept in tubes and under close observation for 

 a week to ten days but by the fifth or sixth day the petioles are 

 apt to become so dry even during the rainy season that the 

 beetles, larvae and coccids become demoralized. The modifica- 

 tions of behavior thus induced will be considered in the sequel. 



There is, perhaps, nothing very remarkable in the fact that 

 both the beetles and their larvae feed on the nutritive paren- 

 chyma of the Tachigalia, since other Silvanidse, e.g., certain spe- 

 cies of Oryzsephilus, Silvanus, Cathartus and Nausibius are 

 known to be vegetarian, but the fact that both the imaginal and 

 larval Coccidotrophus actually solicit and imbibe the saccharine 

 excrement ("honey dew") of the coccids, is so unusual and start- 

 ling that it will be advisable to give a more detailed account of 

 these insects and of their treatment by the beetles. 



The adult female Psendococcus bromelix (Fig. 9) measures 

 nearly 3 mm. in length and is broadly and regularly elliptical, 

 evenly convex dorsally, flattened ventrally and of a pinkish flesh- 

 color or pale dull red, but the body is so completely covered 

 with snow-white wax as to be scarcely visible in healthy speci- 

 mens. The wax is secreted in a thin, even, mealy layer over 

 the dorsal surface but around the periphery of the body as a 

 regular fringe of stiff, blunt pencils which are longest on the 

 posterior segments, somewhat shorter on the anterior border 

 of the head and still shorter along the sides. Large specimens 

 of the insect are less numerous in the petioles than the smaller 

 or recently hatched individuals, many of which scarcely exceed 

 .5 mm. in length. These are reddish because they have not yet 



