98 Psyche [June 



other species of Trachymyrmex, not in populous files like the 

 species of Atta sens, siricto, Acromyrmex and Moelleruis, and bring 

 in caterpillar excrement and bits of green and withered vegetable 

 debris with which to replenish the substratum of their gardens. 

 Microscopic examination of these shows that they have essentially 

 the same minute structure as those cultivated by other species of 

 Atta. The brown, triturated substratum is enveloped and shot 

 through with a delicate, ramifying mycelium on which numerous 

 glistening white clusters of food-bodies are formed as pyriform 

 swellings at the ends of the hyphse. In my former paper I em- 

 ployed the name "bromatia" for the clusters ("Kohlrabihaufchen" 

 of Moeller) and that of "gongylidia" for the hyphal swellings 

 ("Kohlrabikopfchen" of Moeller), but Neger ^ has recently sug- 

 gested that the term "ambrosia" be given to the hyphal modifica- 

 tions produced and eaten by all fungus-growing insects, i. e., by 

 the ants and termites as well as by the Ipid (Scolytid) beetles 

 for which the term "ambrosia" was originally suggested by 

 Schmidberger as long ago as 1836. I am quite willing to accept 

 this term and to abandon my own nomenclature. 



The only insects that could be suspected of myrmecophily in 

 connection with T. arizonensis were a number of small, j^ellow, 

 wingless, cockroaches which I found in the superficial galleries of 

 a nest in Hunter Canyon. These cockroaches, however, were not 

 species of the genus Attaphila, which Berg and I have taken from 

 the nests of the large species of Atta, but were probably merely the 

 young of some much less remarkable cockroach and were behav- 

 ing as scavengers. The same species was also found in the upper 

 galleries of several other ants in the same locality, especially in 

 nests of Odontomachus clarus. 



2. Atta (Trachymyrmex) desertorum sp. nov. (Fig. 2). 



Worker. Length 2.5-3.5 mm. 



Head, without the mandibles, as broad as long, slightly narrower in front than 

 behind, with feebly convex lateral and straight or nearly straight posterior border 

 and angularly rounded posterior comers. Eyes hemispherical, in front of the middle 

 of the head. Mandibles with two larger apical and several minute basal teeth. 

 Clypeus flattened, with its anterior border sinuately reflected. Frontal area triangu- 

 lar, rather distinct. Frontal carinae with angular external borders and flattened 

 but not concave surfaces; continued back as a pair of diverging ridges to the pos- 



1 Ambrosiapilze. Ber. Deutsch. Bot. Gesell. 1908, Bd. XXVI. Heft 10, pp. 735-754, 1 pi. 



