The complicated social lives of insects

Most insects are solitary, meaning the live their lives alone expect for mating. There are some insects, however, that have more complex social structures. Insects (and other animals) can be classified by their social arrangements. The most common categories of social arrangements are presocial, subsocial, communal, quasiscocial, and eusocial.

Presocial: Some otherwise solitary insects come together at certain points in their lives to build new nests or participate in mating. These are called presocial insects. Subsocial: An insect that cares for it’s young but does not interact with it’s peers is subsocial. The ground nesting bees I wrote about in an earlier post are subsocial because they provision their young with food. Communal: Insects that live in a common dwelling but care for their own young are communal. Some types of bumble bees are communal because they build a shared, underground nest but each female cares for her own young. Quasisocial: Similarly to communal insects, quasisocial insects also share a dwelling. But the young (often called brood) are care for collectively. Eusocial: Eucosial insects share a nest and cooperatively care for the young. Additionally, they have reproductive castes and that adult generations overlap. Reproductive castes means that only some members of the nest are allowed to reproduce. For example, only queen bees lay eggs while the other bees have different tasks such as foraging and caring for the young. Overlapping generations means that the young and multiple generations of adults are present at the same time. Eusociality is somewhat rare and is confined to two insect orders: Isotera (termites) and Hymenoptera (ants, bees, wasps). All termites are eusocial as well as all ants. Bees and wasps each have each have about 600-700 eusocial species. Honey bees are the most common example.

Now that the terminology is out of the way, I want to talk specifically about termites. They mostly get attention for being destructive, but really they are very interesting insects. By sheer numbers and range, they are one of the most successful insects. Termites are found on every continent except Antarctica! They live in large colonies and have an extensive caste system that divides labor: workers, soldiers, and reproductives.

Workers are the numerically the largest caste although they are physically the smallest. Their job is to find and digest the cellulose in wood and provide food for the colony. They are small and usually light colored. Below are pictures of eastern subterranean termite workers peeking their heads over ground.

Soldiers are physically larger than the workers. Their job is to guard the workers and the nest. In many species the soldiers have large jaws. In fact their jaws are so large they cannot eat and have to be fed by the workers! I do not have a good picture of a soldier, but this video on youtube is a pretty good demonstration of how big and aggressive they can be.

The reproductive caste is established at the start of a new colony. Only one male and one female, called the kind and queen, will reproduce in each colony as long as they are alive. This is different from the eusocial Hymenoptera, which only have queens. Heirs to each position are also kept in the colony in case one of them dies. Kings and queens are larger than the other castes. Below is a picture from http://lpm.net.au/termite-management/termites/ that shows a huge queen, the smaller kind and soldiers guarding them.

termites

The queen produces workers and soldiers to maintain the colony but also new reproductives to create new colonies. This is how a colony reproduces. The new reproductive termites have wings and leave the colony to go found new colonies.

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Often this happens all at once, called a reproductive swarm. This is a video of subterranean termites coming up in a reproductive swarm. And this is what the swarm looks like as it’s trying to disperse. Reproductive swarms often happen in spring when the ground is moist so keep an eye out for them! Hopefully you will see them while out hiking and not near your house.

This social structure has worked well for termites. They have been successful for millions of years and will likely continue to be.

 

 

 

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About keviclaire

I recently graduated from the Department of Environmental Science, Policy and Management at UC Berkeley. My research interests are focused on biological control and how to increase it's use in agriculture and home gardens. I am also an avid gardener and insect photographer. I'm using this blog as a place to share those interests!

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