1. Bombarding Beetles Erica Nadeau

2. Classification ColeopteraAdephaga Carabidae DytiscidaeCincindelidaeGryinidaePolyphaga

5. The Bombardier Beetles These tribes make up what are known as bombardier beetles: Paussini (flanged bombardier beetles) Metriini Branchinini (‘typical’ bombardier beetles)

6. Pygidial Glands These beetles all have paired pygidial glands with similar structures. The glands produce the chemicals responsible They secretions are expelled in slightly different manners

7. Pygidial Glands Epidermal in origin Contains a reservoir chamber, and a reaction chamber. Lined in most places with a thin layer of cuticle

8. SEM of the Pygidial Glands

9. The Reaction Hydrogen peroxide and hydroquinone are produced in the glands (g). Once produced they migrate to the reservoir chamber (R) When the beetle is in need of defense, muscles squeeze the reservoir chamber, moving the liquids to the reaction chamber (r)

10. The Chemistry + other catalyses and peroxidases

11. Bombardier? What is the bombardier effect: The spray is ejected from the body at very high temperatures, and with precise aiming The high temperature comes from an exothermic reaction undergone in the reaction chamber An excess of oxygen is created in this reaction, aiding in the speed at which the spray leaves the beetle Also gives an audible popping, or crackling sound

12. Paussinea Group that contains the tribes Metriini, and Paussini Primitive Flanged bombardier beetles Uses Coand ă Effect Myrmecophiles

13. Metrius contractus Of the tribe Metriini The most primitive of the Paussinea – They don’t spray – No flanges – Fused elytra

15. The Flanges

16. Coand ă effect Widely used in engineering Accounts for the annoying tendency of liquids to curve around spouts, and trickle down the sides of glasses Paussinae is perhaps the first example of a biological mechanism using this effect

17. Flanges and the Coand ă Effect

18. SEM of the flanges The hairs provide possible scattering of the secretion, as well as retaining droplets after spraying Beetles wipe the hairs, getting the toxic spray onto their legs

19. The Spray

20. To flange, or not to flange? When the spray gets ejected anteriorly, the abdominal tip is pressed upward, connecting the lip with the flange For posterior spray, the abdominal tip is not pressed against the flange, directing the spray more downward

21. Something a little more exciting

22. Slight modifications Flanges disappear, however abdominal tip is more muscular and dexterous Excretory duct is on the abdominal tip Can direct spray with the most accuracy For sprays over the top of the body, cuticular reflectors are used

26. References Eisner, T., Aneshansley, D.J. ‘’Spray aiming in Bombardier Beetles: Jet Deflection by the Coanda Effect” Science Vol. 215, No. 4528, pp. 83-85, (Jan. 1, 1982) Kanehisa, K., Murase, M. “Comparative Study of the Pygidial Defensive Systems of Carabid Beetles” Appl. Ent. Zool. 12 (3): 225-235 (1997) Eisner, T., Aneshansley, D.J. ‘’Spray aiming in the Bombardier Beetle: Photographic Evidence” Proc. Natl. Acad. Sci. USA Vol. 96, pp9705-9709 (August 1999) Eisner, T. et al. “Spray Mechanism of the most Primitive Bombardier Beetle (Metrius contractus)” The Journal of Experimental Biology Vol 203, 1265-1275 (March 23, 2000)