Gnat and Sandfly

Gnat noun - Any of various small biting flies: midges; biting midges; black flies; sand flies.

Sandfly and gnat are semantically related. In some cases you can replace term "Sandfly" with "Gnat", this nouns are similar.

Sandfly noun - Any of various small dipterous flies; bloodsucking females can transmit sandfly fever and leishmaniasis.

Gnat and sandfly are semantically related. You can use "Gnat" instead a noun "Sandfly".