EXPERIMENT STATION BULLETINS. 



2G1 



the northwest, the direction in which lie the nearest mosquito breeding 

 pools. 



DISEASE OF THE MOSQUITO. 



On August 5, Mr. Barlow found a number of adult mosquitoes killed by 

 a fungus, EntomopMhora sp. nov. They were very numerous on the mar- 

 gins of one of the pools in the north woods, sometimes almost covering the 

 soil and the pieces of bark to which they clung. Some were just killed and 

 showed little, "if any, external growth, and some were covered with a dense 

 dull white growth. All were within a few inches of the water and all 

 faced away from it. Imagine thousands of mosquitoes all headed away 

 from the water as if they were trying to get away from it. 



Fig. H.— Mosquitoes killed by disease, nat size, original. 



It would seem that the effect of the disease is to draw the affected 

 insects to the water, possibly by creating a thirst, after slaking which the 

 insects, in trying to retreat, are caught and stopped in their course by 

 numerous rhizoids or anchor ropes which are sent out by the fungus in 

 the body to fasten the victim permanently to the place where its ill luck 

 overtakes it. Unfortunately for the mosquito host, the diseased individ- 

 uals die just in the right place to infect their fellows as they go to the 

 pool to drink or to lay eggs. This is a case where the fungus seems to 

 influence the host in such a way as to lead to the spread of the disease. 

 Similar impulses seem to be induced in the case of other species, — the 

 Sporotrichum that is used against chinch-bugs seems to impel the diseased • 

 individuals to hide under clods or in other moist and protected places, 

 just ihe places Avhere the young bugs come to shed their skins or to molt. 

 This is of course the best j)0ssible way to spread the disease. Then, too, 

 in the case of the common grasshopper disease, Empiisa grilli, the dying 



