Can anyone help me to rephrase with the below sentence as it is misplaced modifier
An expert on Diptera and fossil insects, Hennig’s ideas were applicable to all organisms.
[Although he was primarily] An expert on Diptera and fossil insects, Henning's ideas were applicable to all organisms [not just Diptera and insects].
The first part of this sentence is an introductory subordinate clause. The omission of the conjunction "although" is a matter of style, and may depend on the context.
Edit: this kind of introductory clause is called nominative absolute.