14 



Psyche 



[February 



spot. An examination of the soil in the fields revealed quantities 

 of the worms below the surface at a distance of six inches to one 

 foot. November the 7th and 8th, long after the grasshopper sea- 

 son, the ground now cold was again broken and the nematodes 

 were found coiled up at about the same distance below the surface. 

 Undoubtedly they hibernate in these positions. 



During the highest mortality we made a series of dissections in 

 order to determine the per cent, of parasitism. On a place called 

 the Halladay Farm, we obtained the following astonishing high 

 figures by the dissection of M. bivittatus. 



Sept. 



On a place called the Tarbox Farm, we dissected about equal 

 numbers of M. bivittatus and M. atlanis and obtained the following:: 



Sept. 8. 100 9 9 dissected and worms found in 22%. 



" " 25%. 

 " " 25%. 

 " " 3%. 

 " " 5%. 



In both series of dissections it will be noticed that the percentage 

 of parasitism in females is much higher than in males. Since the 

 life-history of the worm is still so obscure we are at present unable 

 to offer any explanation for this fact. 



How the grasshoppers become infected is unknown. Since the 

 nematodes are so large when they leave the grasshoppers in order 

 to burrow into the soil, we are under the impression that grass- 

 hoppers are the secondary hosts. It is difficult to imagine what 

 animal might constitute the primary host. Perhaps some other 

 insect may furnish the clue to this interesting question. 



Next summer we hope to extend our observations and attempt 

 to gain a more complete insight into the life-history of this Mermis 

 parasite. Some parasites fluctuate so numerically from one seasoni 



