Tribe 16. Attapseniini 



This is a recently recognized, monogeneric, wholly myrmecophilous tribe. 

 At present it holds two species, one from Brazil and one from Argentina. Since 

 both species are adjusted to the society of leaf-cutting ants {Atta sexdens L.) 

 there is the possibility that the exact ecology of these species can be worked out, 

 and also that additional species can be discovered with other kinds of leaf- 

 cutting ants. 



The chief structural points may be summarized as follows: 



Head subhexagonal with short, oblique tempora; eyes large, reniform in 

 lateral view, composed of large facets; vertex with the usual pair of vertexal 

 foveae; a short antennal tubercle on each side of the narrowed front. In the 

 genotype the front is sharply, longitudinally bicarinate from the vertexal foveae 

 to the antennal tubercles, with the intervening space between the carinae sulcoid. 



Mandibles with five to six teeth. 



Maxillary palpi presumably only three-segmented ; first segment elongate- 

 cylindrical (true second palpomere?), obliquely truncate; second slightly obcon- 

 ical and not much longer than wide, slightly longer and distinctly wider than 

 first; third (distal segment) subovoidal, slightly more than one-fourth longer, 

 and distinctly wider, than second, with a short, blunt, palpal cone at apex. The 

 maxillary palpus is not as long as the maxillary cardo! Such reduced mouth- 

 parts are intermediate between the Arhytodini and Tyrini, and the myrme- 

 cophilous habitat suggests a parallel with Clavigerinae. In the latter case, how- 

 ever, the rudimentary clavigerine mandible suggests a much more complete ad- 

 justment to the society of the host ant, while the toothed attapsenine mandible 

 suggests the primitive predatism of pselaphids. Such speculation, in the absence 

 of direct ecological experiments, leads to the conclusion that this new tribe plays 

 the role of the synoekete in the Atta society. 



The antennae are eleven-segmented, with a compact funicle and poorly de- 

 veloped club. This condition is approached by Endytocera and Barrojuba in 

 the Jubinini, and to a less extent by Ephiinia of the Hybocephalini and Juxta- 

 hamoto'psis of the Tyrini. 



Pronotum lacking either basal foveae or sulci. 



Elytra inclined towards the abdominal impression noted later ; each elytron 

 with a sutural stria but lacking basal foveae, discal striae, sulci, and impressions. 



This total absence of pronotal and elytral foveae and sulci is a very spe- 

 cialized feature for pselaphids. 



The abdomen is also specialized in the direction of the Clavigerinae. The 

 abdomen, as a whole, forms a perfect oval with the elytra, and has a deep, 

 subelliptical basal depression. An oblique carina limits the sides of this depres- 

 sion, giving a sharp and triangular wall ; the basal fourth of the lateral carina, 



(348) 



