NOSEMA AS A SOURCE OF JUVENILE HORMONE IN PARASITIZED INSECTS

¹ Department of Biological Sciences, Purdue University, Lafayette, Indiana

1. In Tribolium the infection of Nosema stimulates growth of the host, but deters development to the adult state. Infected Tribolium larvae pass through as many as six supernumerary molts, resulting in giant larvae which weigh twice as much as uninfected controls.

2. Surgical transplants of Nosema to allatectomized Blattaria prevent adult development and a nymph is produced at the next molt. If the parasites are confined to a small chamber affixed to the nymph, but open to the nymph's hemocoel, the same effect is obtained. If such a chamber is separated from the host with a Millipore filter preventing migration of the parasites while allowing passage of the active principle, the allatectomized nymph does not metamorphose. These experiments prove that Nosema is capable of replacing the hormone normally produced by the host's corpora allata.

3. Parasite spores have been extracted by the techniques used to purify natural juvenile hormone and the resultant extract has juvenile hormone activity in tests performed on Hyalophora cecropia pupae and allatectotomized Blaberus craniifer. The extracted material, however, does not have sufficient farnesol isomers to explain the juvenilizing effect.