We must be careful when we go to catch insects. Some insects are poisonous

One fine day,when Charles Darwin was still a student at Cambridge,the budding naturalist tore some old bark off a tree and found two rare beetles underneath. He’d just taken one beetle in each hand when he spotted a third beetle.Stashing one of the insects in his mouth for safekeeping,he reached for the new specimen when a sudden spray of hot, bitter fluid scalded his tongue.Darwin’s assailant was the bombardier beetle.It’s one of thousands of animal species,like frogs,jellyfish,salamanders,and snakes,that use toxic chemicals to defend themselves in this case, by spewing poisonous liquid from glands in its abdomen.But why doesn’t this caustic substance,ejected at 100 degrees Celsius,hurt the beetle itself?