In China: An Assassin Bug with an Ant Carcass Disguise - Observation of the Week, 3/15/20

Our Observation of the Week is this Acanthaspis fuscinervis assassin bug, seen in China by @jishenwang!

I can’t speak for everyone, but I usually relax for a bit after finishing dinner. Entomology PhD candidate Ji-shen Wang and his family, who live in the Yunnan province of China, go outside for a run after their evening meal (“a family tradition”) and come across incredible insects.

 “On our way back home,” he recounts, “my mom shouted with a great curiosity: ‘What? Is this a moving ball made of soil?’ 

Luckily I know this is an assassin bug nymph, which covers itself with debris and corpses of its victims as camouflage. The next day, I went to the same place and photographed some more bugs. When I show my mom and dad my macro photos of the adult (see below) and immature bugs, they could hardly believe their own eyes. "This ball of soil has legs and antennae!" my mom said. “No way this little soil ball would become a stinging bug like this!” my dad said.

The Reduviidae family, also known as the assassin bugs, are a group of predatory “true bugs”, and like other bugs (Order Hemiptera) have mouth parts adapted to piercing and sucking. Many of the bugs we commonly see, like aphids, hoppers and cicadas, tap into plants and slurp up their juices, but as you might expect, assassin bugs dine on other animals. 

Unlike many other familiar insects such as flies and beetles, bugs undergo “incomplete” metamorphosis, and grow through a nymphal stage  rather than a larval stage, which more closely resembles the final adult stage. And as Ji-Shen noted above, the nymphs of Acanthaspis fuscinervis excrete a sticky substance which they use to attach dirt and dead ants (not the bodies of any other prey) onto their bodies. Joseph Stromberg of Smithsonian Magazine writes that researchers studied the efficacy of this camouflage with jumping spiders, a common predator, and found that “[the[ spiders attacked the naked bugs roughly ten times more often than the masked ones.” So it seems pretty effective! 

Growing up in a very biodiverse area, Ji-Shen (above, photographed by his mom) was always interested in nature but says he was “obsessed” by insects and over the last six years has been researching the Panorpidae family, commonly known as scorpionflies, as a PhD candidate in the Entomological Museum, Northwest A&F University, Shaanxi Province of China. 

Ji-Shen has been on iNat for just over five years, and he tells me

iNaturalist benefits me in two ways: 1) I can share my observations with people around the world, and quickly know what species I am recording; 2) I can find a lot of useful information through other people’s observations. For example, a new distributional record of a species, a never-reported interesting behavior, and vivid colors of a living scorpionfly, which are obscured in the museum specimens. iNaturalist is actually a very beneficial companion to my personal life and scientific works! I usually spend at least half an hour on iNat each day to share my observations and check other's interesting posts.

- by Tony Iwane. Some quotes have been lightly edited for clarity and flow.

- Ji-Shen started a scorpionfly project on iNat.

- And you can take a look at his research publications here.

- Lacewing larvae also encrust themselves with debris and carcasses.

- Assassin  bugs are pretty cool, here are the 50k+ Reduviidae obserations on iNat!

Posted on 15 de março de 2020, 09:23 PM by tiwane