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Wasp: Metapelma sp. (Eupelmidae, Chalcidoidea)
This large female scarab, still with remnants of mud from her emergence from the ground, was approached almost immediately by a small metallic green parasitic wasp (last photo). The wasp climbed up onto the back of the beetle and began to explore and examine it from all angles. I am not sure if she deposited eggs into the beetle, but her ovipositor was certainly long enough for the job. The beetle was about 3.5 cm long and the first of this species to appear this year. (The males have a small thoracic horn).
Both insects came to an ultraviolet light in the garden, San Cristobal de Las Casas, 2,200 meters.
Spotted on May 19, 2013
Submitted on May 30, 2013
8 Comments
Thank you John and Chalcidsrule for the identification of the wasp. All the information is so interesting and unusual that this wasp was interested in the scarab if it is normally associated with wood-boring beetles. All very neat indeed.
Thanks for the comment chalcidsrule. I knew that Metapelma were associated with wood boring beetles, which is another oddity about this one because this is a scarab which lives in the ground. Never mind - just when you think you know something about chalcid biology something pops up to show just how little we do know. At any rate, it is nice to know that I haven't completely lost my eye now that I have gone over to the dark side in administration.
maybe the wasp just wanted a better view... :-)
Thanks for sending the URL John. You are certainly correct, it is a female Metapelma. I have collected many off of dead trees because species of the genus are larval/pupal parasitoids of woodboring beetles, but certainly not parasitoids of adults.That said, I have not seen anything like this. There is no prior suggestion that females might be phoretic and travel on the scarab to where it oviposition sites. This wouldn't be terribly effective anyway because phoresy is normally associated with parasitoids of the egg stage, which are parasitized soon after the eggs are laid. The only thing I can think of is the adult scarab is emitting some chemical cue that is also present in the larval tunnel and which helps the wasp locate its potential host hidden within the trunk. Interestingly, mid June is about the time Metapelma is also active up here in Canada.
Thank you John. I thought this was just too cool also. A tiny glimpse of a side of life we don't often get to see. I am so happy the wasp is identifiable. I'll wait for your final word. I wish I could have seen her oviposit, if she even ever did.
Lauren
This series is too cool. I am pretty sure that the wasp is a Eupelmidae (Chalcidoidea) - and looking at the enlarged/flattened hind leg, possibly even in the genus Metapelma. I will send the url to a friend of mine to see if he has any better suggestions.
In terms of the biology - it is not all that usual to see the wasps going after adult stages (it does happen, but it is an exception). So it is a very nice series of pictures. Not sure the exact biology, but the wasp certainly wouldn't hang around very long if she wasn't interested.
Thank you Mark. I think the wasp probably parasitized the beetle. She was just too interested for too long.
Interesting spotting Lauren.