As with all members of the genus
Pepsis, females of
Pepsis mexicana capture and paralyze large theraphosid spiders (
tarantulas) as a source of food for their
carnivorous larvae. After stinging and paralyzing the tarantula, the female wasp drags it into the tarantula's former
burrow or within a previously excavated nest. A single egg is deposited on the
abdomen of the victim, then loose soil is compressed over the spider and egg. Both male and female
Pepsis wasps feed on
nectar of various
flowering plant species. ==Painful stings==