16 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



In the conidiophore stage on the tree the fungus hyphae break forth 

 in groups from between the body segments and extend out as long 

 slender threads, which in turn branch and form numerous fruiting 

 organs. This stage of the fungus has been taken only from adult 

 thrips on the tree and not from the larvae, and it has been found 

 present almost everywhere that the pear thrips has been collected. 



There is no doubt that the fungus spends a part of its life on the tree 

 and a part in the ground, the rapidly fruiting stage among the active 

 thrips and the heavy-walled dormant stage within the hibernating 

 individuals in the ground; but we can only surmise how it is carried 

 from one to the other. The bodies of the larval thrips witliin the 

 ground are all absorbed by the fungus and naturally, therefore, the 

 spores must be carried to a new host before they can germinate to 

 any great extent. We have found adult thrips in the ground whose 

 dead bodies contained only a few spores and others which developed 

 some of the external mycelial growth wdthin their cells. If this were 

 often the case, and these individuals in the ground produced fruiting 

 spores as they do on the trees, it would be an easy matter for healthy 

 individuals in coming from the ground to become accidentally infested 

 and to carry the parasite up to the tree where, because of the gre- 

 garious habits of the insect, it would spread rapidly. 



The fungus grows readily in the nutrient agar under ordinary con- 

 ditions and seems to retam its virulence and can be transferred from 

 cultures to the living thrips. The fungus may prove to be a check 

 for the pear thrips, but its effectiveness is uncertain because it is so 

 subject to climatic conditions. , 



