Subject: Pale-Painted Sand Wasp* (Bembix pallidipicta)
*this species doesn’t have a common name, so I created this common name by using the etymology of its scientific name “pallidipicta” which seems to mean “pale-painted”.
Location: Parents’ Farm, Norfolk County.
Date: July 2013.
For an Introduction to this series (my Top 20 Nature Photos of 2013-2020) go here.
The Story Behind the Shot: While growing up, my brother and I discussed several times the idea of a project: to list every single species that occurred on our family’s property. While this project never reached fruition, the idea of it has inspired me throughout my adventures with the creatures in my own backyard and elsewhere. One day several years ago I spent a day just wandering around on my parents’ farm taking photos of every interesting creature that caught my eye. I was amazed to find busy little wasps digging burrows in the sand at the edge of the field. Despite their frenzied activity I managed to capture one at the entrance of its burrow.
The Story Behind the Species: Bembix pallidipicta is one of those Sand Wasps (members of the subfamily Bembicinae) I’ve mentioned once or twice on my blog about a year ago now. The following information on this species is summarized from Evans and O’Neill (2007).
Not all Sand Wasps construct burrows in sand, but B. pallidipicta does, usually selecting large areas of loose sand to begin their burrowing. Nest site selection is fine-tuned in that they require a small amount of moisture in the sand to maintain a fine crust when they tunnel beneath it. The sites where the females emerge and the males mate are often suitable for the females to use for their nest construction, so unless the habitat is disturbed the same site can support a population of sand wasps for multiple generations. B. pallidipicta males gather around sites where adult females will soon emerge, and fly in short hops, which gives the appearance of “aggregations of very small toads” (Evans 1957).
Once their burrow is constructed with a chamber up to 56 cm beneath the surface (the depth is partly determined by the dryness of the sand), the females lay a single egg at one end of the chamber (termed the brood cell). This egg will hatch and the wasp larva will wait within its subterranean chamber for its mother to provide food. B. pallidipicta exhibits what is called “progressive provisioning” which means that the mother brings prey in multiple times to the larva while it is growing and feeding. I’ve always loved this aspect of sand wasps because it’s essentially the same setup as songbirds awaiting worms in their nests. For B. pallidipicta, the prey is all true flies (Order Diptera) of several Brachyceran families, including Flower Flies (Syrphidae), Horse Flies (Tabanidae) and House Flies (Muscidae). When bringing fresh prey to her larva, the mother will push the fragments of partially eaten prey off to the side, and block this debris off with sand. This likely helps prevent parasites or diseases from accumulating within the nest, or it’s possible that it’s a way for the mother wasp to judge how much more prey to provide. Because B. pallidipicta nests in large unrelated groups, females will occasionally steal prey from other females nearby to feed their own offspring. After about 4 days of feeding, the larva pupates and the mother moves on to construct a new nest.
My top 20 Nature Photos of 2013-2020 are going to be presented in chronological order of when I took the photos, they aren’t arranged in any other sort of hierarchy. Come back next time for a photo of a much larger animal caring for its young…
For previous posts about Hymenoptera, see:
Evans, Howard E. Studies on the Comparative Ethology of Digger Wasps of the Genus Bembix, cited in Evans, Howard E. and O’Neill, Kevin M. 2007. The Sand Wasps: Natural History and Behavior.
Evans, Howard E. and O’Neill, Kevin M. 2007. The Sand Wasps: Natural History and Behavior.