Small World Discoveries

HYMENOPTERA > APOCRITA | Aculeata > Crabronidae > Philanthinae (Philanthidae)

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It wasn’t that many years ago that this impressive wasp was considered to be one of Britain’s great aculeate rarities with only a handful of known populations. Fortunately, that situation has changed, as the species is now widely distributed across much of the south where it can be found on coastal dunes or inland habitats where there’s open sandy ground such as on lowland heaths.

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Philanthus triangulum is commonly known as the Bee-wolf as the females stock their nest burrows exclusively with bees, primarily worker honeybees. The prey is caught and paralysed by a sting before being taken back to the nest site, which is a deep burrow containing a number of chambers, each of which needs to be provisioned with several bees. It is estimated that over a hundred bees may be collected by a single female Bee-wolf through the summer flight period that usually spans early July to mid-September. After hatching, the larva feeds on the cache of honeybees before spinning a cocoon to hibernate through winter, ready to emerge in spring. 

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At the start of the mating season, males gather together in a form of lek, where each will defend a small territory and uses pheromones in order to attract a female. After this, the males play no further part in the nesting process of either digging the burrow or provisioning the nest cells.

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The females are relatively large (up to 17mm body length) imposing wasps, most easily recognised by the narrow reddish stripe behind the eye and their extensively pale face. The smaller males have a distinctive trident-like marking on their face and have striking bluish-coloured eyes.

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I was rather lucky to find two small nesting aggregations on my local heath during the summer of 2021 and, by visiting a few times, was able to put together a pretty good selection of images; a number of which are featured in the 'slide deck gallery' below. They show females at their burrows and bringing back prey, as well as taking a bit of time out to rest and, in one shot, what happens when they inadvertently poke their head into another wasp's burrow! At the end there are three photos taken at a different nesting site at Hartland Moor where the final shot is the only photo here of a male. 

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The slideshow photos can be viewed and manually cycled through at this size. Two images that show good detail have been duplicated below, but set so that they can be magnified when clicked. 

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