This probably is Hesperomyces virescens, from the order Laboulbeniales (Fungi, Ascomycota). It uses a haustorium to penetrate the host’s integument, making contact with the haemocoel and drawing nutrients from it. The haustoria only cause deformation, no life-threatening damage.

In spite of their parasitic nature, most Laboulbeniales, including the ones forming a haustorium inside the host’s body, seem to have little or no effect on the reproduction and survival of their host. There are some papers with information on particular hosts that demonstrate a shorter life span and/or a decreased number of offspring. This is, however, certainly not the rule in Laboulbeniales.
When heavily infested by Laboulbeniales, the host may become a suitable prey for predators since it will not be able anymore to fly or move properly. The parasite doesn't kill its host but causes physical disabilities.

De Kesel (2011) suggested that, considering its actual prevalence and thallus densities, the introduced coccinellid Harmonia axyridis has become the "main host" of Hesperomyces virescens (in the specific studied area, i.e. National Botanic Garden of Belgium, Meise). However, it is expected that the prevalence of Hesperomyces virescens may increase on native coccinellids.

Feel free to contact me at dhaelewaters[at]fas.harvard.edu. I'm studying these amazing creatures for my PhD.

Best,
Danny

Thanks so much.