Moesz Gusztáv - Soós Lajos (szerk.): A Magyar Természettudományi Múzeum évkönyve 28. (Budapest 1934)

Hungerford, H. B. ; Evans, N. E.: The Hydrometridae of the Hungarian National Museum and other studies in the family. (Hemiptera)

It was found that the ratio of segment II to segment I variec? from 2.05 to 2.33 in the males with a mean ratio of 2.20; in the females the variation of the ratio of segment II to segment I was from 1.94 to 2.23, the mean ratio being 2.06. The ratio of segment II to segment IV varied from 0.65 to 0.81 in the males, the mean being 0.725; for the females the variation was from 0.64 to 0.81, the mean being 0.743. The lengths of the antennal segments of six males and six females of Hydrometra Myrae BUENO from Calcasieu Parish, Louisiana, were also measured. In the males of this species the ratio oi segment II to segment I varied from 2.50 to 2.80, the mean being 2.65; in the females the variation was from 2.34 to 2.61, the mean being 2.42. The mean ratio of segment II to segment IV was 0.91 for the males and 0.94 for the females. In the following descriptions of new species a unit of measurement is aqtial in length to 0.0325 mm except for those marked with an asterisk in which the unit = 0.0333 mm. A change in eyepiece micrometer was responsible for the variation in the unit. The difference is trifling and far within the variation of a species. Since we have found no species of Hydromeira common to both Hemispheres we have chosen to treat the genus under the two great geographical divisions, Eastern and Western Hemispheres. This will suit the convenience also of those who wish to utilize the keys presented in this paper. Key to Hydrometra of Eastern Hemis ph e r e. 1. Clypeus deeply excavate and thus bifurcate. (See plate I). H. bifurcata sp. u. Clypeus not deeply excavate (2). 2. Clypeus with two elevated callosities, anterior margin excavate. Female with hair tufts on last segment and venter of last abdominal segment greatly produced H. Chinai sp. n. Not as above (3). 3. Clypeus truncate to slightly excavate on anterior margin (4). Clypeus truncate to slightly rounded or conate (16). 4. Hair tufts present on sixth ventral abdominal segment of male (50. No hair tufts on sixth ventral abdominal of male (12). 5. Hair tufts on first genital of male (6). No hair tufts on first genital of male (9).