Cordyceps is a genus of ascomycete fungi, the most famous of which is the species that parasitizes the vegetable caterpillar — Cordyceps sinensis that has long been considered a precious ingredient in Chinese traditional medicines. All Cordyceps species are parasitic, mainly on insects and other arthropods (they are thus entomopathogenic fungi); a few are parasitic on other fungi like the subterranean, truffle-like Elaphomyces. The mycelium invades and eventually replaces the host tissue, while the elongated fruiting body (stroma) may be cylindrical, branched, or of very complex shape. The stroma contains many flask-shaped perithecia (sing. perithecium): hollow, flask-shaped structures usually embedded in the stromatic tissue that contain many long, cilindric asci. These in turn contain the filiform (thread-like) ascospores, which easily break into fragments and presumably constitute an infective stage.
The genus has a worldwide distribution and more than 300 species are currently known — most have been described from Asia (notably China, Japan, Korea and Thailand). The genus has many anamorphs (asexual states), of which Beauveria (possibly including Beauveria bassiana), Metarhizium, and Paecilomyces (section Isaria) are the better known, since these have been used in biological control of insect pests. Cordyceps species are particularly abundant and diverse in humid temperate and tropical forests.
Each fungus has its own target. EACH FUNGUS HAS ITS OWN TARGET!
Why only insects?
Its just a matter of time.