124 HEMIPTERA-HETEROPTERA. 
Fam. HYDROMETRIDZ. 
The three subfamilies of Hydrometride are all represented in Central America: the 
Hydrometrine by three, and the Veliine and Gerrine by numerous species. The 
Veliine include many species of Rhagovelia and Microvelia, and afew of Velia. With 
one exception, Trochopus salinus, all the Central-American Hydrometride known to 
me live upon the surface or margins of freshwater pools or streams. 
Subfam. HYDROMETRINZ. 
HYDROMETRA. 
Hydrometra, Latreille, Précis des caract. gén. des Ins. p. 86 (1796). 
Limnobates, Burmeister, Handb. der Ent. 1. p. 210 (1835). 
A genus containing about a dozen described species, and generally distributed. 
They are slender, stick-like, sluggish insects, and have the habit of walking about 
slowly on the surface of the water in sheltered spots. Five American species have 
been described and one other is now added, but it is possible that these are not alli 
specifically distinct. The Central-American forms may be separated thus :— 
Rostrum not extending beyond the eyes; antennz.about two-thirds the length 
of the body. 
Ante-ocular portion of the head more than twice the length of the post- 
ocular portion, the head moderately dilated at the apex and slightly 
thickened at the base . . . . . ww ee ee ee ee Carta, Gur. 
Ante-ocular portion of the head not more than twice the length of the 
post-ocular portion, the head considerably dilated at the apex and 
thickened at the base . . . . . . . ew eee eee Centipes, 1. sp. 
Rostrum nearly reaching the base of the head; antenne one-third the length 
of the body; ante-ocular portion of the head twice as long as the post- 
ocular portion. © 2. 1. 1 ee ee ee ee ee ew ee mensor, B. White. 
1. Hydrometra caraiba. 
Hydrometra caraiba, Guér. in Ramon de la Sagra’s Hist. fis. polit. y nat. de Cuba, Ins. p. 173°. 
Gerris caraiba, Leth. et Sev. Cat. gén. Hémipt., Hétéropt. mi. p. 60°. 
Hab. Panama, David, Panama city (Champion).—ANTILLES, Cuba !”. 
A winged female and a brachypterous male from the State of Panama agree 
sufficiently well with Guérin’s description of H. caraiba. They have the ante-ocular 
portion of the head nearly or quite two and one-half times longer than the post-ocular 
portion ; the rostrum does not extend backwards beyond the eyes; the pronotum has 
a whitish or grey, black-bordered median line, and its surface is very distinctly 
punctured ; the metanotum is as long as the pronotum; the hind coxe are separated 
from the intermediate coxe by a space about one and a half times greater than that 
