Appendix: https://www.furaffinity.net/view/42424771/
Haechida are a type of insect known for abducting and infesting animals which have testicles with the intent of propagating. This is accomplished by drones, usually transformed humans, immobilizing their victims and dragging them inside their nest, which is in fact their queen's abdomen. While the queens themselves are rarely larger than a human, they will burrow into caves with nutrient rich soil and draw on the nutrients so that their abdomen may grow. After some time, their abdomen will intertwine with their cave, forming the fleshy innards of their nest.
Once inside, the victim is adhered to the fleshy walls by the natural secretions of sticky slime. While the victim is unconscious, a haechida ant will merge itself with the victim's penis and fusing its egg sack with the victim's testicles. This results in the victim's penis growing exponentially and transforming into something that resembles a large segmented grub. They lose the ability to become fully erect, since the transformation causes their penis to become soft and squishy. Despite this, their penis gains the ability to wiggle and writhe, albeit at the behest of the merged haechida ant. The new autonomy of the victim's penis aids in the birthing of haechida larvae, which are conceived within the victim's scrotum and birthed from their urethra. The black barbs at the bottom of the victim's altered penis serves to assist in stimulating their genitals, which aids in the birthing process.
During the birthing process, the victim is met with intense orgasm that often renders them immobile and unable to think clearly. Rather than sperm, the victim's ejaculation is that of a thick and heavy slime designed to lubricate the larvae's birth. Despite the larvae being insect in nature, they are in fact the offspring of the haechida ant and the infected individual, as their sperm was used to create said larvae within their scrotum. Eventually, the larvae mature into haechida ants, and seek to merge with another victim's genitals.
Once an individual is capable of reproducing haechida larvae, pheromones are secreted from the victim, signaling the function of the queen's abdomen to begin absorbing them into her body. Once fully absorbed, their organs begin a mutation process and their minds become connected with the hive while their genitals continue to produce more larvae. Their assimilated genitals will continue to produce haechida larvae until the haechida ant's supply of eggs are exhausted, at which time their remains are fully processed into the queen's abdominal structure.
There have been instances where victims are able to escape from the nest prior to being absorbed. Unfortunately for these individuals, it is impossible for their genitals to revert to normal. Augmentations that could revert their physique only work on fully human DNA, of which their genitals are not. Also, the removal of the merged haechida ant is nearly impossible without amputating the penis. In the instances where the removal was successful, the victim is still left with a grub like penis, albeit fully under their control rather than partially. Despite this, the victims are still able to live normal lives so long as they are castrated to prevent the conception of future haechida larvae. Even after castration, the victims are still able to experience orgasm and will still ejaculate slime during climax. However, their day to day lives are often met with new challenges, as the autonomy of their penis often results in their penis wiggling around even while clothed, stimulating the barbs and often causing unwanted sexual pleasure.
Pictured above, we see a captured individual with a haechida ant fully merged with her genitals, undergoing the early stages of the absorption process into the queen's nest.