Agave Snout Weevil

This insect is called the agave snout weevil (sometimes referred to as sisal weevil), scientific name Scyphophorus acupunctatus. Here's what one site says about it:

Agaves are relatively problem-free, except for the aggravating agave snout weevil (sometimes referred to as sisal weevil). This destructive and voracious insect seems to prefer the larger, broad-leafed species. Infested plants will show leaf wilt, followed by total collapse of the plant. If this occurs, promptly remove and destroy the infected plant, as well as any weevils and grubs you can find. Drenching the soil with a systemic insecticide can help control problems as well. From para. 9 of http://www.mswn.com/MSWNamazingagaves.ht... read morem

Here are a few more sites with more info:

http://ag.arizona.edu/urbanipm/insects/beetles/agaveweevils....
http://www.hgtv.com/hgtv/gl_cacti_succulents/article/0,1785,...
http://home.att.net/~larvalbugrex/agaves.html