Sentence:  And sometimes, the bugs themselves are the predators, the killers and consumers of elk. / I think of the green-headed horsefly and its bloody conspirator, the <WSD>sorehead</WSD> roundworm—"Elaeophora schneideri". 
Meaning of the word marked with <WSD> tags:  Infection in sheep by the nematode (noshow=1); elaeophorosis.