Are there parasitoids of mosquitoes ? (other than nematodes)
It happens I just found an answer to my question in a recent review book by George Heimpel and Nicolas Mills. It appears that for now we do not know any  parasitoid of mosquitoes.

Quoting chapter 1 :


  "Most insect herbivore species are attacked by
  one or more parasitoid species, but some major
  arthropod pest groups appear to be entirely free
  of parasitoid attack. For instance, we know of no
  parasitoids that attack mosquitoes or other biting
  flies with aquatic larval stages, and no parasitoids
  that attack phytophagous mites or adelgids."


Source:
Heimpel, G., &amp; Mills, N. (2017). Definitions and Interactions. In Biological Control: Ecology and Applications (pp. 1-18). Cambridge: Cambridge University Press. doi:10.1017/9781139029117.003