The 1st-5th instars of Abedus breviceps Still, collected from a Texas population, are described and illustrated. They can be separated most easily by overall body length and width, and by the length of the mesonotal wing pads.
Keffer, S. L. and McPherson, J. E.
"Descriptions of Nymphal Instars of Abedus Breviceps (Hemiptera: Belostomatidae),"
The Great Lakes Entomologist, vol 21
Available at: https://scholar.valpo.edu/tgle/vol21/iss4/7