The bee emerges to the surface during the spring season, and by that time the nematodes has developed into a mature female producing eggs within the bumblebee; 1st larvae stage.

[4] Once in the host, the uterus and other related reproductive counterparts of the female S. bombi turn inside out, allowing for the uterine cells to stretch out and expand into a sac.

The sac, also known as a prolapsed uterus, is composed of an ovary, oviduct, and sperm, and is found all over the body of the parasite.

These “bumps” on the parasite's body bulge into bigger sacs to create a larger surface area for absorbing nutrients from the host via pinocytosis.

[5] At this stage, the nematode is nothing but an enormous uterus filled with eggs, with a tiny appendix containing the remaining organs.