Cockroaches Evolve Distaste for Sweets
Glucose-baited cockroach traps quickly lost their effectiveness after they were introduced in mid-1980s and researchers at North Carolina State University think they know why: evolution.

The study published in Science discovered a glucose-aversion among German cockroaches, which despite their name are found all over the world. In fact, samples were collected from United States, Russia, Puerto Rico and South Korea. Glucose-averse roaches were found in 7 out of 19 populations. These roaches avoided jelly that contained glucose and spat it out when force-fed, even shaking their heads in disgust.

Study researcher Coby Schal says the mutant roaches have changes in the gustatory receptor neurons (GRNs) that detect bitterness.

“The cells that normally respond to bitter compounds were responding to glucose in these cockroaches so they’re perceiving glucose to be a bitter compound” Schal explains. “The sweet-responding cell does also fire, but the bitter compound actually inhibits it – so the end result is that bitterness overrides sweetness.”

Schal calls it an evolutionary arms race between humans and cockroaches, which clearly have a leg up on us.