Sentence:  The males of "P. portalis" [bees] are strikingly dimorphic: fewer than 50% of them are “normal” winged males that mate with females at flowers, and the remainder are large, flightless, <WSD>macrocephalic</WSD> fighters that remain in the natal nest, where they fight to the death with competitors. 
Meaning of the word marked with <WSD> tags:  Having an abnormally large or elongated head.