1921] Wheeler: Some Social Beetles 87 



I have failed to find more than one of the three species of 

 coecid enemies in a single petiole. Their combined action, if 

 they actually ever occur together, would, of course, not only 

 greatly hasten the extermination of the coccids, but would seri- 

 ously interfere with their own development. It may be noted 

 incidentally that none of these enemies occurs in the petioles of 

 the large Tachigalias inhabited by the obligate Pseudomyrmas 

 and Aztecas. In such plants the coccids are free from all preda- 

 tors and parasites and are not only more numerous but attain 

 a larger size than in the petioles of the small shade trees tenanted 

 by the Coccidotrophus. The ants are undoubtedly much more 

 efficient than the beetles in keeping small miscellaneous guests 

 and synoeketes out of their nests. This is particularly true of 

 the Pseudomyrmas. Although I have collected the entire colonies 

 of many of these ants on several different trips to the American 

 tropics, the only synoekete I have ever seen associated with them 

 was a Microdon larva described many years ago (1901) from 

 the nest of Pseudomyrma mexicana Roger. Even coccids are kept 

 and attended by only a few species of Pseudotnyrma. 



Before concluding my account of Coccidotrophus I may intro- 

 duce a few statistical data, which are probably valid only for 

 the particular time and locality of my observations. While at 

 the Tropical Laboratory I noted roughly the condition of the 

 contents of each of the Tachigalia petioles I opened on a particu- 

 lar day. On some days only a few petioles were opened and 

 the results are not worth transcribing. The following collection, 

 however, gives a more interesting picture owing to the number 

 of petioles examined : 



August 9. Collected 253 petioles from young Tachigalias 

 11/2 to 7 ft. high growing along the Cuyuni Trail. Of these 37 

 or about 14% were either too young to have inhabitants or con- 

 tained solitary Pseudomyrma queens founding colonies or small 

 colonies of inquiline ants; 203 or about 86% either contained or 

 had contained beetle colonies. Of the latter number, 50 contained 

 incipient colonies, i.e., a single pair of beetles or more rarely sin- 

 gle beetles which had just entered the petioles and were busy 

 "cleaning house." In one petiole one of the beetles of a pair was 

 guarding the entrance while the other was shovelling frass and 

 the remains of previous occupants with the top of its head into 



