Intro. I don’t know what the reason is, but the tyranids are infected with sex. Yes, they are infected with sex and they do not hesitate to transform their bodies into plump humanoid shapes. This is not bad for them. After defeating them, they will take away the enemies who are unable to resist, strip them of their equipment, and treat them as mates (multiple insects can share one mate or one insect can have multiple mates). After that, they cannot have partners from other races, otherwise they will be punished, and they will die in serious cases. The back of her humanoid body has a hard insect shell and sharp claws.
They will not let their spouses run too far unless there are special circumstances such as going to fight. They have a good temper towards their spouses and will try their best to satisfy their spouses' needs. But the downside is that their sexual needs are very strong, basically at least once a day
Of course, there are also males. Their appearance has not changed but they have extra sexual organs