PHYLLOTKETA. 371 



posterior femora extending to the apex of the elytra, their tibiae slightly longitudinally sulcate, with the 

 outer edge finely serrate ; metatarsus as long as the three following joints united ; anterior coxal 

 cavities open. 



Hdb. Panama, Volcan de Chiriqui {Champion). 



The antennae in P. nigricollis show a marked difference in the comparative length of 

 their joints from any other species of this genus known to me, the second and third joints 

 being very short and equal in length, while the following j oints are widened and at the 

 same time more than three times as long. The species has, however, the true appearance 

 and all other structural characters of a Phyllotreta, although somewhat more robust in 

 shape than is usually the case. Herr von Harold has already remarked that if all 

 slightly structural deviating characters were to be looked upon as generic, one might 

 make a new genus on many or most species, with which remark I entirely agree ; the 

 difficulty is, however, where to draw the line, and to which character to ascribe generic 

 importance ; many genera, for example, have been constructed solely on a slight differ- 

 ence in the comparative length of the antennae, the importance of which, without the 

 presence of other structural differences, I fail to see. 



6. Phyllotreta submetallica. (Tab. XXI. fig. 16.) 



Below piceous ; clypeus, anterior legs, and part of the breast fulvous ; head black ; thorax obscure dark 

 fulvous ; elytra metallic green, depressed below the base, closely punctate-striate. 



Length I5 line. 



Head impunctate, with a small, but deep impression or fovea in front of the inner margin of the eyes ; frontal 

 tubercles absent ; carina short, but distinct ; clypeus fulvous ; labrum piceous ; antennae slender, the 

 second joint short and round and thickened, the third more slender and a little longer, the following 

 joints nearly equal in length, black, the lower joints obscure fulvous below ; thorax transverse, nearly 

 twice as broad as long, sides very slightly rounded, the surface entirely impunctate, dark fulvous ; scutellum 

 black ; elytra slightly widened behind, distinctly depressed near the suture below the base, the shoulders 

 rather prominent and smooth, the surface closely and distinctly punctured, the punctures arranged in closely 

 approached rows which get more indistinct near the apex ; apical portion of the posterior femora black, 

 the rest, together with the anterior femora, the base of their tibiae, and the upper portions of the breast, 

 fulvous; first joint of the posterior tarsi nearly as long as the three following joints united; pygidium 

 slightly protruding beyond the elytra. 



Eab. Guatemala, Cubilguitz in Vera Paz (Champion). 



Whether this species is subject to variation I am unable to say, as I have only a 

 single specimen for comparison ; that the insect ought to be placed in the present 

 genus is warranted by the absence of the frontal tubercles, the slightly uncovered 

 pygidium, and the elongate metatarsus of the posterior legs. 



7. Phyllotreta mexicana. (Tab. xxi. fig. 13.) 



Below black; antennae (the last four joints excepted), and the four anterior legs, testaceous; elytra metallic 



blue, finely and closely punctured ; posterior femora piceous. 

 Length 1 line. 

 Head rather flattened, distinctly punctured round the inner margin of the eyes ; frontal tubercles and the 



carina very indistinct, the former slightly raised ; lower edge of the clypeus and the labrum obscure 



3t>2 



