Cannibalism is a well known aspect of insect and arachnid life. Many insects are genetically geared towards cannibalism, while many others are just too lazy to find other sources of food. Cannibalism is not a bad idea for insects and spiders since nutrients are plentiful in members of the same species. The most well known form of cannibalism is arguably sexual cannibalism. This form of cannibalism occurs when a female spider eats her male suitor. There are plenty of pop culture jokes about how this brutal behavior is personified in human romantic relationships. But there are many different types of cannibalism, and most insects will indulge in at least one type on certain occasions. It may be surprising to learn that even social insects sometimes resort to cannibalism. It may seem counterproductive for insect colony members to eat each other, but certain circumstances make cannibalism a necessity even among the most social of insects. Termites, for example, will sometimes eat their own kind under certain conditions.
Termites, like all living organisms, require nitrogen in order to survive. Microbes use nitrogen in order to grow by capturing the gas from the atmosphere. Once this occurs, nitrogen enters the food chain and is consumed by plants and animals. A termite’s cellulose-only diet offers a relatively small amount of nitrogen for growth. Scientists have long wondered how termites meet their nitrogen needs while subsisting on a diet consisting of nothing but cellulose. Although cellulose contains a very small amount of nitrogen, researchers found that termites failed to grow properly when consuming nothing but wood. It is now understood that termites in the wild consume nitrogen from other sources–their fellow colony members.
When termites are required to meet their nitrogen needs they may resort to a behavior that scientists have termed “controlled cannibalism”. If a termite, or several termites, become injured, then they become food for the rest of the able-bodied colony. During stretches of time when nitrogen containing food sources are low, extensive cannibalism occurs. In these cases even non-injured colony members are targeted for supper. A study carried out several decades ago showed that nitrogen deprived termites were more likely to resort to cannibalism to meet their nutritional needs. In addition to cannibalism, termites will acquire nitrogen by consuming exoskeletons that are discarded by molting termites. Termites have even been found gathering around molting termites in order to quickly snatch up the exoskeletons that are left behind. Although termites may be social insects, they are certainly not civilized.
Do you believe that nutritional needs serve as the most significant motivator driving insect cannibalism?