More Lockyer Valley wildlife
Large Cuckoo Wasp – Stilbum cyanurum (Vinegar Hill)
Some of the most spectacular wildlife in the Lockyer Valley isn’t necessarily the big stuff like kanagroos, koalas or kookaburras. The small stuff can be absolutely entrancing.
The Large Cuckoo Wasp above is one example. It was found dead on the floor in our house (hence the bits of detritus caught up in its exoskeleton). Before you start thinking that we are a bit casual with our housekeeping, the critter itself is less than 20mm long, so the “fluff” is actually fairly minute particles. Having said that this species is so small, it is known as the Large Cuckoo Wasp, which suggests that in general Cuckoo Wasps are pretty small insects.
Just how small they are can be seen in the image below.
The individual in the photo at the top of this page is on the right here. The one on the left is a different species (one of the two shown below). This Australian 20 cent coin has a diameter of 28mm.
The females of these wasps parasitise the nests of mud wasps, laying their egg in the mud nest next to that of the host species. If they are discovered in the nest they roll into a ball like an armadillo, to protect themselves from the sting of their much larger host with the armour plates of their outer skeleton. It seems to be a common feature of Cuckoo Wasps that the surface of the exoskeleton is pitted; perhaps to increase its strength, or to foil the probing sting of an angry mud wasp? The defensive posture is often also used if they are threatened in some other way – such as a human trying to capture them.
The “appendage” at the rear is the ovipositor, used for laying eggs. I’m curious about the structure of this ovipositor – you’d think that an insect that just lays its egg in the open nest of another wasp wouldn’t need something as robust as this to do the job. Some other species of parasitic wasp have large teeth on the ovipositor in order to ‘drill’ through wood to reach their host(1). For example, in the sawflies the ovipositor is saw-like and is used to insert the eggs into plant leaves, stems or wood(2). Is this a relic from a previous evolutionary stage?
Large Cuckoo Wasps feed on the nectar of flowers in the woodlands, heaths and urban areas which are their habitat.
For a beautiful image of this species, have a look at this shot from Stanley and Kaisa Breeden.
After we found the second, smaller Cuckoo Wasp (dead on a window ledge in the house), and than another small one, I contacted Ken Walker at Museum Victoria and offered to send him the specimens to be identified. Ken was happy to do this and to send me photos of the specimens.
Not only did Ken take fantastic photos, he also spent a lot of time cleaning up all the dust and debris off the specimens and then “relaxing” them so that they could be properly displayed. Compare the photo on the left immediately below to the one at the top of this post – they are the same specimen.
Here are some of his photos. These are photos of the most “diagnostic” parts of the bodies. The scale bars for the whole body photos are 5mm for the top photo and 2mm for each of the others.
Stilbum cyanurum (Photo Ken Walker)
Praestochrysis lusca (Photo Ken Walker)
Chrysis lincea (Photo Ken Walker)
You can find more about this species at the following links:
http://www.brisbaneinsects.com/brisbane_parawasps/CuckooWasp.htm
https://baynature.org/articles/the-cuckoo-wasp-a-gorgeous-parasite/
(2) http://www.qm.qld.gov.au/Find+out+about/Animals+of+Queensland/Insects/Wasps+and+bees
http://www.bowerbird.org.au/observations/60098
Thanks to Ken Walker from Museum Victoria for his willing assistance with identifying these species, and for the many other times when he has provided helpful advice on invertebrate wildlife. Ken is the driving force behind Bowerbird, a huge job which he undertakes in addition to his many other duties, and he manages to produce the monthly issue of the Bowerbird Bugle newsletter.
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