Tribe 13. Gtenistini 



In the neotropics this tribe is poorly represented by four genera and twelve 

 species, one genus and species of which may be incorrectly assigned to the 

 region. 



These are clearly separated from other macrosceline tribes by the key 

 characters: second tarsomere normal, not bilobed; tarsi with two large, equal 

 to subequal claws; pubescence always in the forai of scales. This scaley 

 pubescence has a characteristic structure, as illustrated (PI. IV, 6-11), and 

 is never entirely absent; it is especially dense in the temporal areas, in sulci 

 and foveae of the pronotum and elytra, and at articular surfaces of the ab- 

 dominal segments. In addition, the Gtenistini are separable from the Tyrini 

 by the form of the epistome. In Gtenistini the epistome is relatively very large 

 and expanded or tumid between the labrum and the frontal tubercle, and this 

 tumidity may be so pronounced that the lateral margins of the clypeus are 

 auriculate; in Tyrini the epistome is large but is never laterally expanded or 

 auriculate, never conspicuously tumid between labrum and frontal tubercle. 

 The Gtenistini may be separated from the hybocephaline Ephimia with greater 

 difficulty, although the latter genus never has the greatly expanded epistome. 



The three-segmented tarsi have the last two tarsomeres much larger than 

 the first, but the second is never as long as the third; tarsi have two large 

 equal claws. 



A number of Gtenistini inhabit the society of ants (Bruch, 1929; Gasey, 

 1893; Mann, 1911, 1914, 1924; Wickham, 1889, 1892, 1900). 



Key to the Genera ^ 



Second (apparent first) segment of maxillary palpus with a lateral 

 appendage on external face, this appendage may be long or short, 

 and terminates in a bundle of setae (PI. IV, 22) 2 



Second (apparent first) segment with the external face without trace 

 of tubercle or appendage ENOPTOSTOMUS 



2. Third and fourth segments of maxillary palpus always wider than 



long, transversely ovoidal to transversely triangular 3 



Third and fourth segments always longer than wide, elongate tri- 

 angular to acuminate-fusiform GTENISIS 



3. Fourth segment of maxillary palpus with the apical face rounded, 



and without a terminal palpal cone (not to be confused with an 

 appendage of the external face) (PI. IV, 22) PILOPIUS 



*If the specimen has run to Gtenistini in the tribal key (p. 31), and none of the seg- 

 ments of the maxillary palpi have conspicuous lateral appendages, it is either an unrecorded 

 neotropical genus of Gtenistini or belongs to Ephimia of the Hybocephalini (p. 289). 



(291) 



