FIG. 45.13 Types of signal in different forms of communications. Signals can be (a) visual, as in the male frigatebird’s display, (b) auditory, such as a male frog’s call, (c) electrical, as in African electric fish, which generate species-specific electric pulses, (d) chemical, such as the pheromones with which a queen termite controls her colony, and (e) mechanical, as when spiders “twang” webs to interact.