Ceraphronoidea is a superfamily of parasitoid wasps that occurs worldwide, yet little is known about the life history of this group. The superfamily includes both ecto- and endoparasitoids, sometimes within the same genus (e.g. Dendrocerus)1,2,3. Though ceraphronoids have been reported as parasitoids of at least nine different orders of insects 3–9, there are no reported parasites or parasitoids of any ceraphronoids to date. There is very little known about how ceraphronoids even interact with invertebrates other than their hosts.
While photographing specimens at the National Museum of Natural History (USNM) in Washington, D.C., I found a tiny mite clinging to the metasoma of the type specimen of Ceraphron carinatus. I found a similar mite on the metasoma of another type specimen, Conostigmus schwarzi.
I sent images to the Penn State Insect Identification Lab Director, Dr. Mike Skvarla, who recognized them as a type of mite belonging to the group Astigmata. One unique feature of this group is that many are asexual. “They’re diversifying without sexual reproduction,” Dr. Skvarla says, “but multiple lineages have also re-evolved sexual reproduction after it was lost.”
Dr. Skvarla referred me to Astigmata specialist Dr. Barry O’Connor, Professor & Curator of Insects and Arachnids at the University of Michigan. Dr. O’Connor recognized the mites as deutonymphs in the family Acaridae. As mites mature from larvae to adult, they go through three nymph stages—protonymph, deutonymph and tritonymph.
What are these mites, and what do they do? Do these mites feed upon the wasps, much in the same way that ticks feed upon deer and humans?
Not in this case.
While there are a few highly specialized parasites in the group, most acarids are actually fungivores or detritovores. In many Astigmata, the deutonymph life stage actually lacks mouth parts and cannot feed. Instead, these deutonymphs are phoretic.
Phoresy is a type of symbiotic interaction between different species, where the phoront or symbiont relies on a host to transport it from one place to another. It is a commensal type of relationship in that it benefits the mite and does not harm the wasp.
In Astigmata, the phoretic deutonymph stage is specialized for dispersal. These deutonymphs are nothing more than hitchhikers, catching a ride on the wasps to move between different habitat patches.
Some deutonymphs are generalists in that they are found on many different types of insects, but others are specialists and rely on certain insects to transport them to certain areas or hosts. Unfortunately, we aren’t sure what insects Ceraphron carinatus or Conostigmus schwarzi parasitize or what their natural histories are, making it difficult to determine where they picked up these deutonymphs or where they may transport them.
While looking through European specimens recently, I discovered another mite on the back of the head of a Conostigmus female. Dr. O’Connor identified it as another astigmatid deutonymph, possibly belonging to the family Hemisarcoptidae or Winterschmidtiidae. According to Dr. O’Connor, some hemisarcoptids and winterschmidtiids are generalist phoretics.
Unfortunately, there is as little known about these mites as the ceraphronoids they were found on, but progress is being made on their taxonomy. “I found a lot of hemisarcoptid deutonymphs on parasitic Hymenoptera some years ago in northern Michigan,” says Dr. O’Connor. “All were undescribed at the time, but I did get two new genera described.”
Special thanks to Dr. Mike Skvarla and Dr. Barry O’Connor for their help!
1 Mikó I, Masner L, Johannes E, Yoder MJ, Deans AR (2013) Male terminalia of Ceraphronoidea: morphological diversity in an otherwise monotonous taxon. Insect Systematics & Evolution 44(3–4): 261–347. doi: 10.1163/1876312X-04402002
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9 Mikó I, Deans AR (2009) Masner, a new genus of Ceraphronidae (Hymenoptera, Ceraphronoidea) described. Advances in the Systematics of Hymenoptera.: Festschrift in honour of Lubomír Masner. ZooKeys 20: 127–153. doi: 10.3897/zookeys.20.119