page_title: Mermis nigrescens
section_title: Life cycle
hierarchical_section_title: Mermis nigrescens / Life cycle
context_page_description: Mermis nigrescens is a species of nematode known commonly as the grasshopper nematode. It is distributed in the Americas, Europe, and Asia. It occurs in Tasmania, but it has not been observed on mainland Australia. It has been rarely observed in Africa. It is a parasite of insects, especially grasshoppers.
context_section_description: The adult male and female nematode mate in spring or summer. The male then dies and the female remains in the soil through fall and winter. During the following spring or summer the female emerges after a rainfall event while the landscape is still wet, often early in the morning. It then climbs vegetation, sometimes reaching 2 or 3 meters above the ground. It lays its eggs on plants. The eggs are dark brown or reddish, and are about half a millimeter long. The eggs attach to the plant via filaments called byssi. They are consumed by herbivores along with the plant tissue.
  This nematode is most often associated with grasshoppers. High levels of parasitism have been reported in species such as the two-striped grasshopper (Melanoplus bivittatus), the red-legged grasshopper (Melanoplus femurrubrum), the migratory grasshopper (Melanoplus sanguinipes), the snakeweed grasshopper (Hesperotettix viridis), and the desert locust (Schistocerca gregaria). Once it is ingested by an insect such as a grasshopper, an egg hatches almost immediately, sometimes within an hour. The juvenile nematode pierces the gut with its stylet and enters the hemocoel, the bloodlike fluid that fills the insect's body cavity, acting as a circulatory system. There the nematode absorbs the insect's nutrients, taking glucose directly through its cuticle. It grows and develops over several weeks. The newly hatched nematode is about 0.24 millimeters long; by day 37 it has reached about 5 centimeters. The nematodes grow more rapidly and attain larger sizes in larger insect hosts. More females occur in larger hosts, as well. The nematode is still a juvenile when it emerges from the host insect, and finishes its development in the soil. The insect dies as the nematode exits its body, if not before. The adult nematode does not feed.
caption: M. nigrescens emerging from a great green bush-cricket (Tettigonia viridissima)
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