Julia Boyle, Denon Start

A yellow ambush bug Phymata americana with large pollinator prey on goldenrod. Credit: David Punzalan
A yellow ambush bug Phymata americana with large pollinator prey on goldenrod. Credit: David Punzalan

Ambush bugs, Phymata americana, are found on the tops of flowers waiting to attack insect visitors with their large raptorial forearms. Once prey has been successfully attacked, they liquefy and suck out its contents using their straw-like mouth. The success of an ambush bug in catching prey may depend largely on how much it blends into the flower it is perched on. Ambush bugs vary in color from greenish white to rich yellow, which is similar to the most common flower habitats available in its environment. However, it was unknown if the color variation existing in ambush bugs affected what kind of flower they chose to perch on, and whether they could alter their own color to better match their background.

In our study, we surveyed whether ambush bugs found in the wild tended to match the flower color they were found on, and if this was correlated with how often they had prey. In lab experiments, we followed up by providing ambush bugs a choice between yellow and white flowers, as well as keeping individuals on white and yellow backgrounds to see if they would change colour over time. We found that in the wild, ambush bugs were whiter on white flowers and yellower on yellow flowers, and that better matched individuals were found more often with prey. All ambush bugs in the lab preferred yellow flowers, but this preference was especially strong for individuals who were found on yellow flowers in the wild. Finally, we found the first experimental evidence for color change in this species; ambush bugs were able to become more yellow over time but not whiter, and this was exaggerated when they were kept on a yellow background.

We now know that ambush bugs use a combination of color change and choice of habitat to optimize their ability to catch unsuspecting prey. Overall, this study improves our knowledge of how background matching is achieved in organisms using a combination of complex mechanisms.

Read the paper in full here.