ACANTHOMERID^ 231 



Wings large and broad, with curious hyaline spots on a dark ground colour, when 

 at rest lying flat on each other on the flattened abdomen ; prajfurca usually starting 

 almost opposite the beginning of the last quarter of the upper basal cell, but 

 sometimes almost opposite the base of the discal cell, and there is usually a strong 

 folcl in the wing there which runs back a long way and ends in the subcostal vein 

 near the humeral cross-vein ; cubital fork wide open, as in the Tabanida^ but with 

 its lower branch comparatively longer, beginning far after the end of the discal cell 

 and including the wing-tip, but its wing-marginal space hardly twice as much as 

 that of the adjoining cells ; discal cross-vein placed on the basal third or quarter of 

 the discal cell ; second veinlet from the discal cell starting very wide from the first 

 veinlet, and even sometimes forming a branch from the down-turned third veinlet ; 

 posterior cells five, the fourth one being closed in a more decided manner than in 

 any other eremoch^ta ; small cross-vein present though small, placed at about 

 two-fifths from the base of the discal cell ; ambient vein entire though thin ; alula 

 forming a large lobe ; wing-membrane strongly rippled even back to the basal_ cells 

 and the alula but not ribbed, bare or at least apparently so. Squamse practically 

 absent, or the alar pair a little developed. 



This family shows evident relationships to the Stratiomyidce, Leptidm 

 (especially Xylophagince), and Tabanidm, but is quite justifiably separated 

 from all of them. The very diverse structure of the antennse in the two 

 sexes (of at least some species) is very remarkable. 



The AcantJiomeridcp. consist of about a dozen species of gigantic flies 



which inhabit South America, Mexico, and Trinidad. According to Mr 



Champion they inhabit the forests, alighting on trunks of trees ; a habit 



which tends further to show their relationship to the Leptidce. Fiebrig 



has recently (Zeitschr. fur Wissenschaftliche Insectenbiologie, vol. xi., 



1906) described the larva of a species from Paraguay which lives in the 



trunks of very hard-wooded trees. 



Si/nonymy. —The genus Pantophthalmm Thunberg (1819) has two years priority 

 ovax' AcdntJiomera Wiedemann (1821), but possibly (as Osten Sacken suggests) the 

 two genera need not be absolutely synonymous. 



