These wasps are the main recent cause of deaths in No.6. .
They appear to be of an average wasp, but with a much darker colour around their head and red eyes. They are bigger than most wasps, having a larger abdomen than normal wasps and having much wider and darker wings than most wasps. They are still able to fly around with their wings as normal wasps do.
The parasitic wasps are Elyurias' children. As larvae, they inhabit the bodies of hosts that are ideal for the larvae to grow. Their hosts' instincts and nutrition would be favourable to the wasps via Eluyrias' influence on the hosts. Fitting of being parasitic, the wasps were able to control their hosts as well.
Inside the body they seem to grow in a similar fashion to the growth of a normal wasp. When the wasp is fully grown, it leaves the body by (according to Shion) biting it's way out of the host's neck. While the wasp is fully grown, it essentially eats away the host's life, aging them rapidly, and leaving them for dead. However, in Shion and Rou's case, it whitened their hair and caused a snake-like scar to form on their body.
It is because of Eluyrias' ability to manipulate her children's hosts that No. 6 wished to manipulate her power, and used Safu as Eluyrias' host, as a method to have complete control over the citizens of No. 6