Bald-Faced Hornet - Dolichovespula maculata
It's been a good while since the blog has had images of this fierce insect out and about (and away from the nest). Moreover, there's one other significant reason why this specie returns to the blog for further exploration. Recently, a dear friend shared with me a video featuring a Blackjacket Wasp they jarred, and the resemblance between the two species is remarkable! In fact, one could be forgiven for mistaking one for the other. Given the need to highlight difference between the two, we have this post, which begins with a very important picture (1): a reasonable capture of a Bald-Faced Hornet's face. Quite a fearsome specimen, wouldn't you agree? With those large eyes and sharp mandibles, prey insects stand no chance if they are seized for the colony! However, take note of the following observations regarding the (bald) face of this Wasp: the elongated face and the prominent gap between the compound eye and the top of the mandible. This divide - fittingly termed the oculomalar space - is key to distinguish the Dolichovespula from the Vespula.
This facial space is much smaller in Blackjackets, and other Vespula Wasps by extension, including Yellowjackets. Those Wasps' mandible tops nearly touch the bottom of the compound eye! Given the differences here, might there be some advantage to having a prominent oculomalar space and repositioned mandibles? The biting prowess of this large specie may hold some answers...or maybe it doesn't mean much in the grand scheme of things. Either way, if you wish to confirm the identity of the dark Wasp you find foraging among your flowers or devouring pest insects, you'll need a clear view of the face (done as safely as possible). Not only for the space, but Bald Hornets and Blackjacket Wasps also have differing facial markings. While individuals can be very different, it seems that Bald-Faced Hornets have a bisecting line down their face, and a bar between their eyes which doesn't quite touch the bottom section of the compound eyes. To me, this gives the Wasp's head a skull-like profile! With Blackjackets, the bisecting line is replaced with a small patch close to the mandibles. It's also somewhat possible to use size as a guide, as Bald Hornets seem to be larger than Blackjackets across all castes (queens, workers and males) on average.
Pictures were taken on September 2, 2019 with a Samsung Galaxy S4, and on September 5, 2021 with a Google Pixel 4.
