ZooL— Vol. II.] WHEELER— DOLICHOPODID^. 63 



dichotomic table H. albojlorens Walker and H . chrysologus 

 Walker (described as species of Medeterus), although 

 Osten Sacken believes that he has recognized the former. 

 Walker's M. chrysologus appears to be only a variety of the 

 female of his M. glaber. Osten Sacken includes Say's 

 Medeterus lateralis and M. -pimcti-pennis under Hydro- 

 phorus, but their position here is extremely doubtful. The 

 legs of the former species are described by Say as "whit- 

 ish," those of the latter as "white," neither of which terms 

 will apply to the legs of any of the known species of Hydro- 

 chorus, unless Say refers only to the white dust covering 

 the legs. 



1. Veins of wing blackened throughout 2 



Veins more or less yellow at the base 8 



2. Wing with two conspicuous black spots 3 



Wing with faint spots or immaculate 4 



3. Face of male covered with white dust glaber Walker. 



Face of male covered with yellow dust algens, sp. nov. 



4. Third antennal joint elongated cerutias Loew. 



Third antennal joint not elongated 5 



5. Wings with two faint gray spots pirata Loew. 



Wings immaculate 6 



6. Face of male covered with white dust 7 



Face of male covered with yellow dust parvus Loew. 



7. Thorax with cupreous vittse cestuum Loew. 



Thorax evittate innotatus Loew. 



8. Fore tibia ending in a blunt point philombrius Wheeler. 



Fore tibia truncated at the distal end 9 



9. Tip of fore tibia with a large erect black spine. 



eldoradensis, sp. nov. 



Tip of fore tibia without such a spine 10 



ID. Tip of fore tibia with a pair of small spines on the inner side 



agalma, sp. nov. 



Tip of fore tibia without a pair of spines 11 



II. Basal half of costa yellow; large species. . .Magdalence, sp. nov. 

 Costa yellow only at extreme root; small species, sodalis, sp. nov. 



63. Hydrophorus algens, sp. nov. 

 Plate IV, Fig. 123. 



Male. Length 3.5 mm.; length of wing 4.5 mm. Palpi and face covered 

 with thick brownish yellow dust. Antennae black, as broad as long, with 

 rather prominent ventral projection; arista black. Front and occiput metallic 

 green with golden reflections and covered with brown dust, very thick ante- 

 riorly. Postocular cilia black above, yellow below. Thorax, scutellum and 

 abdomen bronze black with greenish reflections, not very bright; humeral 



