Stings 'n' things - wasps in close-up

After some recent bee-related posts, I thought I'd stick with the Hymenoptera theme for a while and take an uncommon look at a common species, the Common Wasp Vespula vulgaris. First of all, it's important to know how to identify this species - after all it is quite similar to other social wasps of the family Vespidae.

Wasp-face showing the 'anchor' mark between the eyes.

The thorax - note the four yellow dots forming a square between the wing-bases.

So, looking at the wasp-face above, the 'anchor' mark is a good clue - this is found in V. vulgaris and the closely related Red Wasp V. rufa. However, the latter only has two yelow dots on the thorax, so this is indeed the Common Wasp.

Identification aside, I wanted to take a closer look at an often overlooked (and sometimes unpopular as it is defensive of its nest and does sting, and may number into the thousands in a nest) invertebrate. The face clearly shows tufts of hairs, plus punctures on the mandibles, and the antennae have a velvety look to them with the segments only indistinctly separated. Another feature used to differentiate vespid species is the 'malar space' - the gaps between the bottom of the eye and the top of the mandible. In both the Common and Red wasps, this is short, but in some species such as those in the genus Dolichovespula, it is noticeably longer. However, taking a tour of our wasp means starting with larger structures, so here's a side view of the head and thorax, plus one of the abdomen.

Wasp head and thorax in side view

Wasp abdomen in side view

Here we can see tufts of hairs on various structures - the head including behind the eye, leg segments, and on much of the thorax and abdomen. The eye is indented around the antennal base, and the antennal segmentation is more clearly visible. We can also see the overlap of abdominal segments. So, taking a closer look still and moving forward from the rear, what can be seen?

Tip of wasp abdomen

Here we see the tip of the abdomen through which the sting can protrude - the very tip has a couple of tiny protrusions at the lower edge which may help guide the sting, but no other specialised structures are visible.

Close-up of abdominal segment

Looking at the abdomen more closely, it is clear that, as in many insects, the chitinous surface is covered in tiny pits and between these is even finer sculpturing. Such pits or 'punctures' are well-known in beetles - for many species, the lines (or random arrangement) of punctures on the wing-cases (elytra) are used in identification. However, although rarely looked at in wasps, the same structure is present. In some insects, some pits bear tiny bristles, but I have to wonder if they perform a weight-reducing function, somewhat like a honeycomb structure on the outside.

Underside of the mid-section

Underside of the waist in close-up

The mid-section of course has the familiar 'wasp-waist' (legs bases can also be seen just in front of it), but zooming in, the underside of the waist has a shallow groove bearing yet another tiny tuft of hairs. What function this has I can only speculate, but maybe it accomodates the curve of the abdomen when this is brought forward with the hairs providing a sensory function. Coarser, longer hairs are visible on either side.

Tarsal segments

The 'foot'

Close-up of the wing

The general structure of the leg can be seen in the side view nearer the top of the page, but here the tarsi and the foot itself are seen more closely. The tarsal segments bear tiny bristles and stouter spurs and the articulation between two tarsal segments is visible. The presence of spurs on hymenopteran legs is not unusual and may form apparatus for cleaning the antennae. The foot itself has the typical arrangement of a pair of curved claws on either side of a central pad, again with tiny hairs and a few larger bristles - I imagine the functions are split between sensory use and improved grip. The wings are folded longitudinally at rest, and here numerous tiny hooks are visible on the surface, these may help the wings stay together Velcro-style, and there may also be a function in aiding airflow during flight.

The top of the head showing ocelli

Close-up of the mandibles

Close-up of the eye and antenna

Finally we return to where we started - at the head. The top of the head bears small simple eyes (ocelli) while the compound eyes provide more detailed vision via the numerous facets (ommatidia) shown above. The velvety texture of the antennae is revealed to be due to the structure of the surface - numerous tiny holes and protrusions involved in the functioning of this highly sensitive organs able to detect a range of important chemical cues relating to reproduction, feeding and of course the social behaviour of this nest-building species. The mandibles are serrated and well able to chew both food and the wood required to make nest-paper for its predominantly underground nests which are usually in sandy soil although it does sometimes use roof-spaces (Allen 2009). Even the mandible shows tiny hairs and although smooth and hardened, some microstructure as seen on the abdomen (along the darkened cutting edge), plus some tiny pimples. So, we have a common species, but one which provides an excellent example of insect structure and its relationship with function - I guess this is why there are textbooks with titles such as 'Biology - Form & Function'. Also, it's worth remembering that in the last 20 years or so, even this common species appears to have declined in Britain, and in some years can be surprisingly scarce (Baldock 2010). Hopefully the beauty of its structure can help develop a greater appreciation of even our less popular insects...

References

Allen, G. (2009). Bees, Wasps and Ants of Kent. Kent Field Club.
Baldock, D.W. (2010). Wasps of Surrey. Surrey Wildlife Trust, Woking.