1. Egg, 2.6 mm in length.
2. Egg-mass showing arrangement (inside of bark).
3. Egg-slit showing tips of eggs (outside of bark).
4. First instar, length 1.8 mm.
5. Second instar, length 2.0-2.8 mm.
6. Third instar, length 3.0-5.0 mm.
7. Fourth instar, length 5.0-7.5 mm.
8. Fifth instar, length 8.0-10.0 mm.
9. Adult female, 11 mm, 14 mm with horn.
10. Adult male.
These drawings are by W.D. Funkhouser and were originally published in the Annals of the Entomological Society of America. The captions are also Funkhousers.
The main Thelia bimaculata page has photos and more information about this species.