One bond that matches insects is the number of pairs of legs.

I gathered up a whole range of specimens from eggs to the elderly, put them in bottles, and went off confidently the next day to lab, much relieved.

My relief was short lived, however, when the lab assistant became noticeably upset. She pointed out to me that the specimens in my collection had FOUR sets of legs, whereas insects had only THREE !

As such, my specimens were not insects, but arachnids, more commonly known as brown widow spiders.