STEROLS IN LAODELPHAX-STRIATELLUS WITH SPECIAL REFERENCE TO THE UNICELLULAR YEASTLIKE SYMBIOTES AS A STEROL SOURCE

Sterols were analysed to investigate the sterol source in Laodelphax striatellus and three other rice plant-sucking homopterous insects. In L. striatellus, cholesterol, 24-methylenecholesterol and β-sitosterol were detected. The host plant (rice) contained campesterol, stigmasterol and β-sitosterol. From the honeydew excreted by L. striatellus, cholesterol, β-sitosterol and negligible amounts of campesterol were recovered. Laodelphax striatellus possesses yeastlike symbiotes which can be destroyed by high temperature. Fifth instar nymphs, which have been exposed to 35°C for 3 days in their 1 st instar, showed lower cholesterol concentration and markedly reduced amounts of 24-methylenecholesterol. From the results it is concluded that L. striatellus has two sterol sources: one from the host plant and the other from the yeastlike symbiotes which appear to provide 24-methylenecholesterol. © 1979.