This is the 3rd of three individuals. These green apterous water treaders were abundant on Lake Creek in southern Williamson Co., TX. Although not measured in the field, knowing the capabilities of my point-and-shoot camera allows me to estimate that most/all of them were 3 to 4 mm long. Of three N. Am. species of Mesovelia (M. cryptophila, amoena, and mulsanti), only the latter two have been recorded in Texas and the amoena only in s.e. coastal Texas (Jackson Co.)(discoverlife.org). Moreover, a paper by Kort-Gommers and Nieser* suggests that the latter two species can be separated by size, amoena being only 2.1-2.3 mm long and mulsanti ranging from 3.0 to 3.8 mm. I saw a few winged adults but did not get any clear pictures of them--they are extremely fast movers on the water and algal surfaces! I'll upload images of three (presumed) different individuals from the sharpest images I obtained.

* Kort-Gommers and Nieser. 1969. Records of Antillean Water-Striders (Heteroptera). Pp. 75-77, In: Studies on the fauna of Curacao and other Caribbean Islands, No. 112.