Eggs of the tapeworm are passed with the bird's feces and hatch in the water, where the first larval stage, the coracidium, is produced.

Within one to two weeks, the infected copepod is ingested by the second intermediate host, the three-spined stickleback, Gasterosteus aculeatus.

[5] Conversely, in populations where Schistocephalus solidus infects the second intermediate host (three-spined stickleback) it can reach high prevalence, up to 93% in both European and North American populations [6][7] The growth of S. solidus in the second intermediate host is largely dependent upon the environmental temperatures.

[3] In most species outbreeding (mating with an unrelated individual) would be preferred,[9] but advantages and disadvantages of each of these breeding strategies have been argued.

[10] In short, self-fertilization is advantageous when no mating partners are around, but might lead to inbreeding depression—the reduced fitness of offspring because of the unmasking of deleterious recessive alleles due to the breeding of closely related individuals.

Similarly, breeding with a sibling, also known as incestuous mating, also shares some of the same disadvantages as self-fertilization does—inbreeding depression and lack of genetic variation.

But incestuous mating is advantageous because it helps maintain gene complexes within the family which may be important for local adaptation.

Breeding with unrelated individuals might seem to be most advantageous choice of mating because it increases genetic variation and avoids inbreeding depression, but it could be more time-consuming as partners might not always be available.

[13] In species where there is low parental investment and sexual encounters are rare and sequential, incestuous breeding is indirectly beneficial.

If the prospective mates are related there is an increase mutual interest in finding a resolution with respect to playing the unpreferred sexual role.

Phenotype modification, through injecting silicon "parasites", with densities and sizes similar to infective plerocercoids (~150 mg) did not alter behaviour.