Both, for the bug to exhibit an external change (its color), there must first be an internal change that triggers the color change (its color). Thus, the internal change facilitates the external change. The predator is an external factor that causes an internal reaction (maybe it's fear) in the bug, that internal reaction then triggers an external factor which is the change in color. Just a personal opinion.
an invasion of a microorganism from the external environment
One basic internal signal that triggers Cell division is 'the size of the Cell'. External signals that do this exist...
depolarization
external
change it.
asthma has many triggers or causes every person diagnosed wit asma has different triggers such as mold cockroaches and even season change you should know your personal triggers so you can be aware of them
change in daylight length triggers breeding
stimulus
effector
despolarization
1) Performance dips 2) Change in management team ( particularly chief Executive)