Information authenticated by the Environment Agency:
http://www.environment-agency.gov.uk/
Calcareous: Containing free calcium carbonate, chalky.
Larvae: Stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Ovipositor: Egg-laying organ in female insects consisting of outgrowths of the abdomen (the hind region of the body in insects). The stinging organ and poison sac of worker bees and non-reproductive female wasps is a modified ovipositor.