http://www.sciencemag.org/news/2019/04/these-suicidal-aphids-repair-their-home-their-own-bodily-fluids

The gall aphid’s home repair strategy gives new meaning to the phrase “sweat equity.” These insects use their own bodily fluids to patch holes in the walls of their colony’s home—a hollow growth called a gall that forms on the branches of trees where they set up shop. Once an invader pierces the gall, the aphid soldiers lay down beads of a thick, milky fluid from their abdomens and don’t stop until they seal the breach. Some wring themselves dry until they are lifeless husks, others drown in their own secretions, and a few trap themselves outside—all to ensure the safety of their brethren inside the gall.

But scientists didn’t know what this goop was made of or how the gall aphids (Nipponaphis monzeni) produced it. Now, researchers have untangled the biochemical recipe for the aphid’s natural building materials.