Fern fern ("Onoclea sensibilis"). Giant water fern ("Salvinia molesta") is one of the world's worst aquatic weeds. The important fossil fuel coal consists of the remains of primitive plants, including ferns. Ferns have been studied and found to be useful in the removal of heavy metals, especially arsenic, from the soil. Other ferns with some economic significance include: The study of ferns and other pteridophytes is called pteridology. A pteridologist is a specialist in the study of pteridophytes in a broader sense that includes the more distantly related lycophytes. Pteridomania is a term for the Victorian era craze of fern collecting
Larval food plants of Lepidoptera (which often have to be abundant enough). Lepidopteran larvae can often be raised on a variety food plants and commercial mixtures. Closely related Lepidoptera tend to have similar food plant preferences. Many caterpillars sequester the toxins from their food plants and use them as a defense against predators. Though it is common for Lepidoptera to prefer a certain plant genus or family, some species feed on a narrow selection of unrelated taxa. The choice is unrelated to nectar plant preferences of adult Lepidoptera, which are much less strict. Larval food plants of Lepidoptera Caterpillars (larvae) of Lepidoptera species (i.e. of