Effects of water extracts of rescue grass-fed desert locust frass on A. Egg widths (mean ± SD; n = 10) and B. Antennal lengths of embryos (mean ± SD; n = 6–11). Eggs were incubated in sand wetted with the frass extract (treated) or water (control) on day three after oviposition at 30°C. C–F. Photographs show embryos observed on days 5 and 9. Triangles in (A) and (B) indicate the time when the treatment started. Vertical bars in C–F indicate 1 mm. White arrows indicate an embryonic antenna in C–E.