Vielleicht sind Fliegen nicht so klug wie Mäuse, aber doch mindestens so klug wie Tauben.  Es geht hier also nicht nur um reine Zahlen, sondern auch um die Herausforderung für die Fliege, wenn sie alles mit winzigen Nervenzellen berechnen muss.
So at least you'll admit that if fruit flies are not as clever as mice, they're at least as clever as pigeons.  Now, I want to get across that it's not just a matter of numbers but also the challenge for a fly to compute everything its brain has to compute with such tiny neurons.