A war zone inside a leafcutter bee cocoon
After coming across Monodontomerus wasps and then Pteromalus wasps, my next customer to film was this minute chalcid wasp Melittobia acastsa. It is not fussy which bee it targets. In fact it targets several species of bees and even wasps, flies and in the labs of researchers, even beetle larvae. I have found them in Red Mason and leafcutter bee cocoons. This is one mean wasp with gladiator male wasps fighting in the host cocoon!
Gladiator male Melittobia wasps
The blind, winged but flightless and non feeding males fight to the death for access to females inside the cocoon. Hence the war zone in the video. Generally males emerge first and crawl over eggs, larvae and pupae in search for other males, which may be his brothers. If found they engage in a fight to the death. It reminded me of the film Highlander, “There can be only one!” Unless there are so many females, which may be sisters to the males, inside the cocoon, life is then too short to fight and they become otherwise engaged!
According to Brown the unmated females will lay male (unfertilised) eggs. Wait until the first son hatches, mate with him and she is then able to lay both males and females eggs. Whichever host she decides to lay her eggs upon, it is doomed. Females with the typical elbowed antennae, have two forms a short winged and a long winged.
A war zone within a leafcutter bee cocoon
I was amazed once I opened the cocoon. It was literally a mass of heads, limbs, body parts and frass.
With thanks to Dr. Jim Cane USDA for identifying the wasp species and for the correction, that the reddish eyed individuals are pupae inside the cocoon and not prepupae.
Parts of this film were made using my solitary bee observation nest box
For more information see ‘On the Life History of Melittobia acasta, chalcid wasp parasite of bees and wasps’ F B Brown
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