48 



is described. Those on mushrooms frequently begin their attack 

 just inside the skin at the base of the stem, while those hatched in 

 the gills feed in the cap. At a temperature of 55° to 60° F., the 

 average larval period is 23-24 days, at 65° to 70° F. it requires 17-18 

 days. When mature, the larva constructs a cell either in the soil 

 or in the mushroom itself, just below the skin. Pupation occupies 

 7 or 8 days. The adults live 5 or 6 days in captivity, feeding on the 

 films of moisture in the manure or soil, and quickly dying in dry 

 surroundings. 



Original infestation is due to the presence of adult flies in the mush- 

 room houses, and also to importation of the immature stages with 

 the manure. Many eggs and larvae are destroyed during the packing 

 of the soil, but sufficient survive to form a first generation, from which 

 a second is produced in less than a month, and it is the latter generation 

 that oviposits on the first mushroom buttons appearing from 6 to 7 

 weeks after soiling. Larvae from these eggs produce small light brown 

 patches of destroyed buttons and excreta around the mushroom stools, 

 while the succeeding generation causes heavier infestation, the grubs 

 often devouring all but the surface skins of the buttons. The attacks 

 on mushrooms above ground are slight, the few days necessary for 

 their development being insufficient for the larvae to be full-sized 

 or to do much damage. The loss is greatest when straw litter is left 

 on the bed, as this is an ideal breeding-place for the flies. A conserva- 

 tive estimate of the damage in a becl under these conditions was £35 

 to ^40 per crop. 



Natural means of control are almost negligible ; the two great 

 cultural factors are temperature and ventilation. JMany artificial 

 remedies were tested, but very few gave any success without severely 

 damaging the crop, which is a very delicate one. The trials included 

 fumigation of manure with benzine, or powder applications of 1 per 

 cent, dichlorobenzine, 1 per cent, pyridine, pure pyrethrum, 1 per 

 cent, crude quinoline, pure wood tar, and pure derris. Many kinds of 

 traps were also tried. Recommendations suggested for the prevention 

 of infestation, as a result of many experiments, are that houses should 

 be provided with suitable walls and roofs to ensure an equable tem- 

 perature, which for preference should be below 60° F. Ventilation 

 should be adequate, and all vents and doors should be well covered 

 with fine muslin cheese-cloth to prevent invasion from the outside. 

 After an old bed is cleared out and before a new one is put down, 

 a thorough fumigation with sulphur dioxide or hydrocyanic acid gas 

 should be carried out. A second treatment, after the new bed has 

 been soiled, but before the appearance of the mushrooms, will destroy all 

 insects that have emerged from the introduced bed. After the second 

 fumigation, traps consisting of white paper coated with an adhesive 

 should be placed at intervals over the bed, especially under lights ; 

 this will capture practically all the insects that enter through the 

 doors or that emerge from the bed after the second fumigation. These 

 traps should be renewed and continued throughout the life of the crop. 

 Frequent cleaning of the bed and sweeping of the paths should be 

 practised. These measures involve scarcely any expense. 



The second part of this paper, by Mr. Chorley, deals with other 

 mushroom pests, which normally are of minor account, but which 

 under certain conditions increase to such an extent as to endanger 

 or even ruin the crop. Among these is the mite, Tyroglyphus myco- 

 phagiis, the life-history and habits of which are so similar to T. lintneri, 

 recorded as damaging mushrooms in America [R. A.E., A, v, 424] that 



