Couplet 183

183a:  Head vertically narrowed behind eyes to form narrow neck, head not received into prothorax, either bulging beyond pronotal margin, or fitting closely against pronotal margin so that head in lateral view has a posterior carina or crest meeting anterior margin of pronotum

Scraptiidae   p. 441

183b:  Head gradually narrowed behind eyes, fitting into pronotum in a telescoping manner