374 SUPPLEMENT. 



in this exceedingly variable insect the specimens are given as types of mere varieties. 

 The four species described by Walker in his List of Dipterous Insects in the collection 

 of the British Museum (H. purpureus, H. duplex, H. triplex, II. subjectus\ and upon 

 which Mr. D. W. Coquillett based his genus Euhybos, are but forms of one only. An 

 examination of a large series of specimens from the United States shows forms 

 intermediate between all of Walker's types. The Mexican varieties of H. triplex are 

 characterized in the preceding Table of Species ; they are from the following 

 localities : — 



Var. tabascensis, <?, Teapa, Tabasco (H. H. Smith).— Length 4*5 millim. 

 Var. smithi, $ , near Vera Cruz (H. H. Smith). — Length 4'25 millim. 

 Var. yucatanus, $ , Yucatan (Gaumer). — Length 3 millim. 

 Var. bakeri, <£, " Mexico" {Baker). — Length 3'25 millim. 



4. Hybos spinicosta, sp. n. 



J . Similar to H. typicus in the minor details, the description of which will answer for this, with the following 

 exceptions : — Face narrower, dusted with silvery-white. Legs wholly pitchy-black ; the tibial and tarsal 

 bristles are shorter and more numerous, though they occupy the same relative positions. The posterior 

 legs and the abdomen are covered with much shorter hairs. Abdomen not shining, dusted. The 

 hypopygium is terminal and more enlarged. The wings are somewhat infuscated, broader, with peculiar 

 venation ; costa bent at the tip of the first vein, so that the anterior edge of the wing is bowed outwardly, 

 beset with spiny hooks from the junction of the auxiliary vein, these hooks gradually becoming straight 

 about the middle of the wing and passing insensibly into the usual fringe of hairs ; stigmal spot very 

 broad ; second vein strongly curved in an ogee to accommodate itself to the deep stigma, ending much 

 nearer to the tip of the first vein than usual ; third vein straight, subparallel with the costa in the 

 outer part of its length ; discal cell narrow, the cross-vein at its apex perpendicular to the penultimate 

 section of the fifth vein. The halteres are broken, though from the stumps remaining they seem to have 

 been dark. 



Length 4-5 millim., length of wing 4 millim. 



Hob. Mexico, Sierra de las Aguas Escondidas in Guerrero 95U0 feet (H. II. Smith). 

 A single male. 



SYNECHES. 



Syneches, Walker, Insecta Saund., Dipt. p. 165 (1852) . 



l. Syneches quadrangular is, sp. n. 



3 . Fuscous. Mouth-parts yellowish. Mesonotum fuscous, with faint indications of the usual lighter vittae, 

 slightly tomentose. Halteres concolorous with the thorax, pedicel lighter. Abdomen dark brown. 

 Hypopygium small. Legs, including the coxae, yellow ; the hind pair with the apices of the femora, tibiae, 

 and tarsi brown. Wings hyaline, with a single, well-limited, quadrate, dark brown stigmal spot at the 

 apex of the first vein ; marginal cell not widened at the stigma ; third vein not rigidly straight ; veins 

 brown. 



Length 2*5 millim. 



Hab. Mexico, Teapa in Tabasco (H. H. Smith). 

 Two male specimens. 



