Italochrysa italica carrying pieces of woody material
I wrote before about bumblebees rolling balls to get a reward or just for fun. This shows that in laboratory conditions insects can learn to use human-made objects. But what do we know about how insects use objects in nature?
In addition to some insects using objects from their environment to build nests (think for example of anthills), various insects also use small objects in a more active manner, which can be even considered a tool use. Here are just a few examples.
Bait
Larvae of assassin bug’s use the carcasses of termites they previously caught as bait. They gently shake them in front of their heads to attract more victims.
Camouflage and shield
The same bugs cover themselves in clay crumbs. Many other insects’ larvae use objects from their environment in a similar way. They can use for example: exoskeletons of other invertebrates, moults, snail shells, larvae, wood blocks or sand (see photo above). This protects the larvae from natural predators and provides camouflage. Some beetle larvae even collect droppings and carry them on their back for protection. Usually, individuals of a specific species are picky in what type of objects they use.
Sponge for food transport
Some ant species drop various materials (e.g. various soil grains) into liquid food and then take them to the nest. When provided with many materials, even some human-made, like sponges and artificial foam, they selected objects that were best for foraging, according to the physical properties of the materials and the specific foraging environment. Some ants could even modify objects to increase their utility.
Barricades
Bicoloured pyramid ants drop small stones and other objects in front of the entrances to honeypot ant nests. This way they interfere with their competitor’s foraging behaviour.
Pavement
If a surface that red imported fire ants want to cross is sticky or was previously treated with pesticides or repellents, they cover it with soil particles to cross it safely.
Gifts
As part of courtship, males of some insect species present stones, small branches or other objects as gifts. Male dance flies even make their own balloons as gifts. They produce silk-like threads from which they weave a spherical bag around a tiny prey. It shines in the sun and encourages females to mate and distracts them from eating the male.
These are just some examples of object use in insects* and there is for sure still a lot to discover. Some of these behaviours have a strong genetic basis, but others are much more flexible and can be learned individually or socially. It has been shown that there are also individual differences within species when it comes to object use. For example, in some ants, workers that are bolder or show high levels of exploratory and foraging activity are more likely to use objects.
Since insects are the biggest animal group, more object uses are bound to be discovered in the future and maybe insects will give us a better understanding of tool use in animals.
* Taken from the article “Object use in insects” by Wen et al.
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Photo of Italochrysa italica from the article “Debris-Carrying in Larval Chrysopidae: Unraveling Its Evolutionary History” by Tauber et al.