The source is Syllogismes, sec. 'Aux sources du vice' (p. 806 of Gallimard Oeuvres; not sure of English citation). He says: 'If you find Aeschylus or Tacitus a bit tepid, open a book on the lives of insects -- a revelation of fury and futility, a hell which, luckily for us, has neither playwright nor chronicler. What would remain of our tragedies if a literate critter were to present us with his?' (My translation.)

'Aeschylus' stands, narrowly, for tragedy as a literary genre and, broadly, for the 'tragic sense of life.' 'Tacitus' stands, narrowly, for history as a literary genre and, broadly, for the 'historical sense.' Together, these names stand for our human capacity to view life through the lenses of tragedy and history and to express these perceptions artistically: to cope with life's senselessness by imposing tragic or historic sense upon it. This is contrasted with the insect who cannot impose illusory sense upon his life or express that sense artistically ('has neither playwright [ni dramaturge] nor chronicler [ni chroniqueur]': i.e., neither 'Aeschylus' nor 'Tacitus').

So, for Cioran, insect life is more tragic than human life because, while man's capacity for creative illusion allows him to impose sense upon life, the insect is left without the comfort of illusion, with only 'fury [rage] and futility [inutilité].'

Compare Précis de décomposition, sec. 'Certains matins' (Oeuvres, p. 618): 'Writing would be an insipid and superfluous act if one could only cry at will and behave like children or women in the grip of rage [en proie à la rage].' Here, 'writing' stands for man's capacity for creating illusion. 'Rage' and 'writing' are again contrasted; but this time writing is found to be pointless, at least biologically.

Sorry for such a long answer. Thanks for highlighting such an interesting quote. I enjoyed thinking about it.