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Tsala Trails Journal

The Sisterhood of Paper Wasps | On Foot in the African Bush episode III

  • Aug 18, 2024
  • 3 min read

Updated: Jan 16


Paper wasps are social insects that live in female colonies dominated by a single reproductive individual. Come spring, a fertilised female will start a new nest by building hexagonal cells made up of chewed-up plant fibers mixed with her saliva. The result is a very light but tough papery material. 


And she doesn’t stop there! To avoid the nest being raided by ants, the cells are smeared with an ant-repellent secretion produced by her abdominal glands. The worker wasps will also defend the nest by administering very painful stings to anyone they consider a threat. Contrary to bees, the wasps’ stings are not barbed, allowing them to administer venom repeatedly. 


Did you notice the fluorescent green caps on the nest cells? We think the fluorescence properties of the cap may affect how visible light is transmitted inside the cocoon, ultimately affecting how the larvae pupate. That is some next level engineering!



Eggs and larvae of the Polistes Paper Wasp


Once the dominant female or queen has built the nest cells, she lays one egg at the bottom of each of them. Can you spot the white eggs hidden in the top cells? 


When the larvae hatch, the worker females are responsible for feeding them: they will hunt caterpillars and present the chewed-up insects to the larvae. The larvae in turn regurgitate saliva which is consumed be the worker, providing her with carbohydrates, proteins and enzymes she cannot make herself. 


Eventually the larvae reach maturity and the cell is capped with a fluorescent covering so the larva can pupate inside. Once the fully developed wasp emerges, it will join its sisters in helping with nest building and raising their younger siblings. 


How cool is it to see all three stages of development in one photo!



Female Paper Wasp of the genus Polistes


Reproduction (ie. passing on your unique genetic material) is one of the primary goals of all species. But then why are insects like paper wasps social, helping to care for another female’s offspring?


In paper wasps, fertilised eggs become females whereas unfertilised eggs become males. This means sisters share 75% of their genes but mothers only share 50% of their genes with their daughters! Therefore, by not laying her own eggs and helping raise her sisters, a female wasp is contributing to her own reproductive success. This logic may explain why so many Hymenoptera species (wasps, bees, ants…) have evolved to be the only social insects (except for termites)!


When starting to build a nest, females may have to fight for dominance by eating each other’s eggs. When the new generation of females are born, they cannot mate, as there are no males in the colony (the female is only laying fertilised eggs at this point). Their ovaries also do not develop and the aggressive behaviour of the queen towards the young females actually prevents them from developing. 


Once autumn comes around, the queen has no more sperm and starts laying unfertilised eggs that hatch into males. At this point, the colony breaks up. The males fly off to mate with females from other colonies before dying. The mated females will then go into diapause (a state of dormancy where activity is low and the metabolism is suppressed) over the winter months before starting their own colonies in the spring. 


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