Abstract: Phasmarhabditis hermaphrodita is a slug associated nematode that kills many speciesof slugs and snails and is also able to live in the soil on various organic materials. This simplelaboratory study shows how intraspecific competition and substrate can influence thesenematodes. Causal relationships of lipid reserves, length, fecundity and development ofnematodes colonies to different substrates (kidney, slugs, faeces, organic matter and insect), doseand strain (commercial and wild) were observed. We recorded some interesting trends andbehavioral patterns in this nematode. Big differences between wild and commercial strains,especially in the fecundity and development of nematodes colonies, were also observed.