See this image for example.
What are they doing? What is the name of this process?
These matings can be very long
When copulating, firebugs (Pyrrhocoris apterus) form tandems for prolonged periods. Half of the copulations of marked individuals in the field lasted longer than 12 h, and some lasted up to 7 days. (Schöfl and Taborsky (2002))
The likely reason for such a long mating is for males to guard the female to prevent future matings and therefore to prevent sperm competition
males prolong copulations as a form of ejaculate-guarding under high competition with other males. (Schöfl and Taborsky (2002))