138 LAMELLICOENIA. 



MACRODACTYLUS. 



Macrodactylus, Latreille, Earn, nat. du Regne anim. p. 371 (1825) ; Burmeister, Handb. der Ent. 

 iv. 2, p. 56 (1855) ; Lacordaire, Gen. Col. iii. p. 244 (1856). 



A characteristic American genus, spread over the temperate and tropical regions of 

 the continent, though rare or absent in the plains near the equator. Between thirty 

 and forty species have already been described. In studying the very numerous species 

 from our Fauna I have carefully attended to the secondary sexual characters of the 

 male (discovered by Horn and Kirsch) ; but have found that, like all other characters 

 in the genus, they are subject to variation, and must be used with caution. The 

 development of the postcoxal spine, for example, though its normal form seems to be 

 specific, is subject to abrupt change in the same species ; and the number of ventral 

 setse on each side the middle line of the abdomen varies, though, making allowances for 

 some variation, they form a very good specific character. The singular and abrupt 

 modification in the pubescence of the thorax in the females of some of the species, 

 described below in their places, and the many variations in colour and amount of the 

 pile, both above and beneath, show how useless descriptions of species in this genus 

 must be unless founded on a good series of examples. 



1. Macrodactylus uniformis. 



Macrodactylus uniformis, Horn, Trans. Am. Ent. Soc. 1876, p. 185 I . 



Hah. Noeth America, Arizona 1 . — Mexico, Northern Sonora (Morrison). 



2. Macrodactylus variipes. (Tab. vin. fig. 16.) 



A M. uniformi differt antennarum clava nigra, tarsis posticis nigris, articulis basi cinereo-pilosis, corpore 



densissime adpresso cinereo-piloso, elytris sutura et margine plerumque iufuscatis. 

 Long. 10-12 millim. 



Hah. Mexico, Saltillo, Monclova, and Parras in Coahuila (Dr. Palmer), Durango 

 city (Edge), Guanajuato, Oaxaca (Salle). 



Scarcely more than a local variety of M. uniformis. Like that species and the 

 following (M. mexieanus), the male, with very rare exceptions, has a long postcoxal 

 spine, broad and emarginated, or even bifid, at the tip ; and a numerous group (3-5) of 

 long and very strong (almost spinous) tawny bristles on each side of the second to the 

 fifth ventral segments, besides similar irregular spines at the apex of the fifth and on 

 the sixth, and also on the middle of the metathorax. The pile of the upper surface is 

 more compact than in any other known species, and light ashy (not tawny) in colour. 

 As in M. uniformis, the integument beneath is black. 



An example from Parras is figured. 



