Teleomorph state: Ophiocordyceps unilateralis (Tul. & C. Tul.) Petch

Specimens were found attached to the underside of leaves of forest plants. Hosts are ants (Hymenoptera: Formicinae). Synnemata arising from between the head and the thorax. They are slender, light-brown to brown, 3-8 mm long, 50-80 μm wide, composed of compact longitudinal brown hyphae. Hyphae septate, smooth. Conidiogenous cells arising from the hyphae of synnemata. Conidiogenous cells produce a single long, slender phialide with one or two conidia. Conidia hyaline, smooth, ovoid, 4-7 x 2-3 μm. When conidia are spread on to PDA these are very slow to germinate – if at all. In Thailand only one culture was made from conidia growing directly on PDA. Many more isolates have been secured by first spreading conidia onto PDA and then transferring to Grace’s insect tissue culture medium (Wongsa et al. 2005). The original culture from PDA readily produced the Hirsutella in culture. However, most of the cultures made from insect tissue culture medium remain sterile when eventually transferred to PDA. To date, only one isolate has been able to make the Hirsutella when transferred to PDA (Fig.l). Hirsutella formicarum has been found throughout Thailand from Doi Inthanon National Park in the North to Hala Bala National Park on the Malay border. Usually the hosts bite into the underside of leaves. However, occasionally hosts appear to wander to the drip tip of forest leaves and die by biting into the tip and then clinging to the leaf-tip.

Evans, H.C. & Samson, R.A. (1984). Cordyceps species and their anamorph pathogenic on ants (Formicidae) in tropical forest ecosystems ll. The Camponotus (Formicinae) complex. Transactions of the Mycological Society 82: 127-150. Petch, T. (1935). Notes on entomogenous fungi. Transactions of the British Mycological Society 19: 161-194. Wongsa, P., Tasanatai, K., Watts, P. & Hywel-Jones, N.L.(2005). Isolation and in vitro cultivation of the insect pathogenic fungus Cordyceps unilateralis. Mycological Research 109: 936-940.