The reason assassin bugs carry ant carcasses

(Photo deleted because when I originally wrote the post I linked to the London Salmagundi "via," not to the photographer, Kurt (OrionMystery).

At the Not Exactly Rocket Science blog, Ed Yong discusses a paper in the Journal of Zoology which found that assassin bugs covered with dead ants were less likely to be attacked by spiders.

Jackson and Pollard suggests that the ants break up the bug’s form so that instead of a characteristic shape that the spider can tag as ‘prey’, it sees a jumbled mess that doesn’t look like anything it has ever eaten before. It sees the bug, but doesn’t register it as a meal.

An alternative hypothesis would be that spiders can sense formic acid or other toxins in the ant carcasses.