The only Basswood (Tilia) feeding Catocala in North America, with an easily recognized larva (it has a look-alike sibling species Catocala lara Bremer that occurs in northern Asia). Body whitish yellow to yellowish or blackish grey, indistinct thin darker stippled lines all throughout, no A5 saddle/hump, strongly protruding shiny black A8 tubercles (a morph exists with extensive black "checkerboard" patches across much of the body); distinctive black true legs; venter yellow with modest black spots; sparse lateral filaments; head capsule yellowish with variable net-like darker striations.