Phallus
Explanation
The Joke
Two bugs (likely meant to be insects such as praying mantises or spiders, given the context) are lying together after mating. One says to the other, "I hope it's okay with you, I'd like to wait a little before the copulation in order to deny myself pleasure and build anticipation." The other responds, "Honestly, that feels like it's possibly a fetish." The first then adds, "I guess I just see our relationship as a serious one," and the other says, "Plus, like, this time around our post-coital discussion is going to be about sex. Evolution sucks."
The Humor
The comedy here draws from the mating habits of certain insects, particularly species where the female eats the male during or after copulation. The first bug wants to "wait" before mating, which sounds like a standard romantic sentiment about delayed gratification. But the dark subtext is that for these particular creatures, mating is followed by death (being eaten by the partner), so "waiting" and "building anticipation" takes on a much grimmer meaning -- the bug is essentially procrastinating its own execution. The second bug's complaint that their post-sex conversation is still about sex, and that "evolution sucks," reflects the absurdity of being a creature whose entire existence is dominated by a reproductive cycle that ends in being consumed. The humor comes from applying very human relationship dynamics (wanting to take things slow, having meaningful conversations) to creatures whose biology makes such sentiments tragically futile.
References
The comic references sexual cannibalism, a behavior observed in several arthropod species including praying mantises, certain spiders (like black widows and redbacks), and some scorpions. In these species, the female may consume the male during or after mating. The evolutionary logic behind this behavior is debated: it may provide nutritional benefits to the female that improve offspring survival, or it may simply be a byproduct of the female's predatory instincts. The comic also plays with evolutionary psychology and the idea that organisms are "designed" by natural selection in ways that are suboptimal for individual happiness.