135 



on legs 1 foot high. The boards forming the top of the platform were 

 1 inch wide and were placed 1 inch apart. On and after 25th July 

 each day's production of manure was placed on the platform ; the 

 height of the heap thus formed was kept at from 3|-4 feet. The 

 manure was sprinkled every day with enough water to moisten it 

 thoroughly. Water was run into the concrete basin to a depth of 

 -1 inch." Larvae migrating from the manure dropped into the water 

 below and were drowned. At least once a week, the water was drawn 

 off into the cistern and the number of larvae estimated. The results 

 obtained during August and September seemed to show that at least 

 98 per cent, of the larvae were destroyed. An examination of the 

 manure on the platform after 1st October showed the presence of a 

 few scattered puparia and two typical nests. There was no evidence 

 that larvae ever migrated from the fresher to the older parts of the 

 manure to pupate. Old manure does not seem to serve as a breeding 

 place for flies. This is probably due to the decrease in air spaces 

 and the abundance of carbon dioxide and methane. The composition 

 of the gases may be one of the factors which influences migration. 

 Fly counts made before and after the trap was installed, indicated an 

 average reduction of from 67 to 76 per cent. That the reduction of 

 flies did not correspond with the percentage of larvae destroyed was 

 probably due to the presence of several other breeding places withm 

 the range of flight. Two difficulties were experienced in the practical 

 working of the trap, viz., the accumulation of debris on the floor under 

 the platform and the breeding of mosquitos in the water used to drown 

 the flv larvae. Low air temperatures were found to hinder migration 

 and consequently to decrease the efficiency of the trap. Among the 

 merits of the trap are the small initial cost and small amount of labour 

 required for its operation and its adaptibility for use in stables where 

 the daily production of manure is large . It is suggested that conditions 

 which tend to preserve the value of the manure, i.e. exclusion of air 

 and increase of water content, are the same as those which render 

 the trap most effective by securing the greatest percentage of migration. 



Chittenden (F. H.). Harvest Mites, or ♦' Chiggers."— ?7. 5. Dep. 



Agric, Washington, D.C., Farmers' Bull. 671, 26th May 1915, 



7 pp., 3 figs. 

 The larval form of the harvest mite of the genus Trombidium causes 

 great annoyance in the more southern portions of the Central States. 

 Soon after the larvae, which are microscopic, burrow under the human 

 skin, a small red spot appears. The maximum poisonous effect is not 

 usually felt until the second day. Permanent residents in infested 

 regions become immune, either by a toughening of the skin by exposure, 

 or by innoculafcion due to frequent infection. Harvest mites are 

 abundant in damp localities, along the borders of streams and on the 

 edges of woodland. They are most abundant in the tropics and become 

 less numerous towards the north. In North America, they are generally 

 distributed in the Gulf States, up the Mississippi River to Missouri, 

 and through the Atlantic States to New Jersey. The eggs are deposited 

 on the ground. The larva, after hatching, becomes attached to its 

 host. After feeding, it drops off and seeks shelter. In a few weeks, 



