Spawnmothers start out quite similar to normal queen or soldier parasites, as one such spawnmother was able to take Shakaar Edon host without seriously damaging his body. However, in order to grow large enough to spawn appreciable numbers of young, the spawnmother must exit the host's body.
A spawning spawnmother could grow to be four meters long and taller than an average humanoid at its centre. They had the same pincers and tail orientation as smaller parasites but they were so big the pincers were essentially useless due to being immobile. Their rippled flesh was semi transparent, allowing anyone observing to see the thousands of egg sacs growing within.
A spawnmother could effectively remote control host bodies to do her bidding by commanding her offspring with her telepathy, and could also create quite a loud scream. She could also keep a host body alive after sustaining massive damage, including the consumption of vital internal organs, as evidenced by Dexter Remmick's hollowed thoracic cavity, which had no visible outward affect upon him at all. In the event of a spawnmother's death the entire colony would abandon their hosts and flee. (DS9 novel: Unity)
- Dexter Remmick - The spawnmother in the Starfleet HQ attack of 2364 was able to remain in Lieutenant Commander Remmick, as she had only produced a limited number of offspring before her discovery, which occured early in her plans to take control of Starfleet. She, and Remmick, (who may already have been dead), were promptly killed, ending her plans and preventing her transformation into a larger form. (TNG episode: "Conspiracy")
- Shakaar Edon - The spawnmother in the Bajor attack of 2376 initially used Shakaar to get to Bajor. She later left him before his assassination so that she could grow large enough for a mass spawning. (DS9 novel: Unity)