There is an enormously large variety of life already on this planet. Many insects are actually readily considered some of the most Eusocial species on the planet.
Ants, wasps, bees, termites, bees and aphids all evolved eusocial characteristics and there is no reason to think Culex would be restricted in the future to solitary behaviour only.
If there are evolutionary pressures that enable more reproductive success in acting as a group, insects are actually (due to the short life span, rapid expansion, and high degree of environmental dependancy) more likely (and easily quickly) than other classes to become eusocial if it benefits them.
One way could be role-splitting to overcome environmental restrictions, such as Culux needing to venture far for food, but must nest eggs in protected areas due to increasing competition for eating young/eggs, requiring specialised roles. This could easily start the need for intimate social structures that are a common feature of Eusocial creatures.