Defining what constitutes the exotic has absorbed thinkers over the centuries, pitting West against East, primitive against civilised worlds and, in Thailand, insect collectors against health officials.
A months-long craze has now come up against the law in Bangkok, with the arrest of a 28-year-old man called Pisit Pakhawan.
His crime was to be found breeding large, hissing Madagascan cockroaches which he claims were intended as fodder for snakes and crocodiles, but which collectors have been snapping up for 50 baht (HK$9) at the Chatuchak weekend market.
Why would residents of an already cockroach-infested city want to bring a new, fast-breeding strand of pest into their homes?
Part of the thrill, apparently, is the hiss these insects produce by forcibly expelling air through a pair of modified breathing pores. In the insect world, this is rare.
Male Madagascan cockroaches indulge in aggressive encounters where the more one hisses, the more likely one is to win. They ram each other with their horns or shove their abdomens against opponents, and the hisses give information about where their foe is.
Males also hiss during courtship, if courtship is not too strong a word. Congress is achieved in an end-to-end position.
In both cases these insects win by using strength and sound.
Humdrum stuff for any observer of human behaviour, surely. But for Thai collectors, these insects are deemed exotic.
Not so for the health department. Growing to almost eight centimetres in length, living for three years and able to reproduce up to 60 offspring in a 60-day gestation period, these bugs are off-limits, it says.
The craze is incomprehensible to the uninitiated. It evokes fear and loathing in some circles, deep affection in others, and now has the added cache of illegality.