I have heard temples more often than bows. Many sites mention temples, e.g.:
Medem: Medical Library: Introduction to Eyeglasses: Bridges, ... - ... Medical Library.
Printer-friendly format. Introduction to Eyeglasses: Bridges, Temples and Hinges. Keeping the glasses on
your face. ...
http://www.medem.com/MedLB/article_detaillb.cfm?article_ID=ZZZ69YNLH4C&sub_cat=114 search within
this site

But then I found an equal number os sites using the word bows:

BladePro Eyeglasses - How to make Blade Pro Eyeglasses. This tutorial will ... the rims: Now
to add in a bridge and the hinges for the bows to attach to. Select ...
http://psp.tephras.com/tutorials/glasses/