|Achryson surinamum, a typical low desert species|
Those Ceramcycids that suddenly show up in numbers may have eclosed from their pupae a while ago. They then stayed in the safety of the pupal chamber until some external signal woke them up. Only then did they make the final push out of their pupal chamber.
|An adult longhorn waiting in its pupal chamber in a split log on Mt Graham|
Some twig borers instead prepare a thinned out area within the twig where it will snap off during a strong wind (we have plenty of that this year!) and set the beetle free.
So I looked through my photos: this one clearly shows those lines in the pubescence.
Even Hovore and Giesbert wrote: A single adult of this rarely collected species was reared by us from the root crown of living snakewood, Condalia (prob. globosa var. pubescens). Hovore, F.T. and E.F. Giesbert. 1976. Notes on the ecology and distribution of western Cerambycidae (Coleoptera). Coleopterists Bulletin, 30(4): 349-360. JSTOR