fertile
Explanation
This comic plays on the awkwardness of a mother being far too open and clinical about her daughter's reproductive biology.
In the panel, a mother addresses what appears to be a room full of people (possibly at a family gathering or dinner): "Mother, have you considered having unprotected sex with a male today?" The daughter responds with a mortified "Charlotte!" The mother continues matter-of-factly: "It's just that you're at peak fertility around 4 o'clock this afternoon."
The caption below reads: "I was beginning to regret having haplodiploid offspring."
The punchline relies on a biology concept: haplodiploidy is a sex-determination system found in insects like bees, ants, and wasps. In haplodiploid species, females develop from fertilized eggs (diploid) while males develop from unfertilized eggs (haploid). Critically, in eusocial haplodiploid species like honeybees, the queen's female offspring (workers) are more genetically related to their sisters than they would be to their own offspring. This means that from a gene-propagation standpoint, worker bees benefit more from helping their mother reproduce than from reproducing themselves.
The joke is that the mother has "haplodiploid offspring" -- meaning her children, like worker bees, are genetically incentivized to help their MOTHER reproduce rather than reproducing themselves. So the daughter is pressuring her mother to have sex and make more siblings, because in a haplodiploid system, the daughter's genes are better served by her mother having more children than by the daughter having her own. It's a clever inversion of the typical "when are you going to give me grandchildren?" parental pressure, filtered through evolutionary biology. The mother regrets the arrangement because instead of nagging her daughter about grandchildren, her daughter is nagging HER about having more babies.