49 



it is tliought that it may be the same species. During the whole of its 

 hfe, except when in the hypopial stage, the mite feeds upon the running 

 mycehum, thus preventing its spread, and upon the tissue of the 

 mushroom. This mite has been known to cause complete failure of 

 the bed for several weeks. It is particularly abundant in beds pro- 

 tected by straw. If such an infestation occurs in a large house, there 

 is no remedy except removing the bed and thoroughly fumigating the 

 house with either sulphur or hydrocyanic acid gas. Another mite, 

 Histiostotna rostrosierratiim, has been recorded as swarming (jver nuish- 

 room Ixxls in Paris and causing decay in young buttons, and the 

 Tyroglyphid, Rhizoglyphus spinitarsus, is reported as destroying 

 mushrooms in the caves at Reigate As a preventive, the Frencli 

 use lysol to spray the beds before the crop appears, l^xcept for 

 centipedes, the only natural check upon T. mycophagns is a predacious 

 mite, Gamasus sp., which breeds in manure. A new species of Pedicit- 

 loides was observed on the beds, and men working there have 

 complained of slight dermatitis, which may be due to this mite. 



A species of Collembola, Achorutes annatits, Nic, which is abundant 

 on all mushroom beds, is described. Although there is some doubt 

 as to the damage caused by these spring-tails, their presence depre- 

 ciates the value of the crop and lowers the vitality of the mushrooms. 

 Occasionally, for some unknown reason, they become gregarious, 

 appearing in enormous numbers and remaining for a day or two and 

 then dispersing. They are readily attracted to such paper traps as 

 are described for 5. praecox. Spraying the beds with nicotine or 

 lysol before the mushrooms appear is also suggested. As humid 

 conditions are favourable to them, watering should be as light as 

 possible. Other species of Collembola reported as damaging mush- 

 rooms include A. cyanocephaUis, Nic, A. rufescens, Nic, and A. pur- 

 purescens, Lubb. Species of woodlice infesting the beds include 

 Oniscus asellus, Porcellio scaber and Armadillidium milgare. Holes 

 in the stem or cap are frequently due to these pests, and some of the 

 young buttons are prevented from developing. The remedies are to 

 remove all shelters and to prevent access to the bed. 



The preventive measures recommended for 5. praecox will also 

 serve to reduce the numbers of these minor pests. Slices of freshly-cut 

 potatoes poisoned with lead arsenate will help to destroy woodlice, 

 and slugs can be kept off the beds by an application of lime and salt 

 round the paths. A mixture of unslaked lime in the soil before 

 capping is believed to be beneficial. 



Smith (K. N.) & Wadsworth (J. T.). The Carrot and Onion Flies. 

 Some Preliminary Attempts at their Control. — fruit- Cnnc'cr, 



Fruiterer, Florist & Mkt. Gdnr., London, li, no. 1322, 31st 

 March 1921, pp. 575-578, and no. 1323, 7th April 1921, pp. 616- 

 618, 13 figs. [Received 24th November 1921.J 

 Some preliminary efforts in the control of Psila rosae (carrot-fly) 

 and Hylemyia antiqua (onion-fly), which are very serious pests, 

 particularly in Lancashire and Cheshire, are recorded. The damage 

 to carrots is caused by the larvae of P. rosae burrowing into the root 

 and tunnelling in the outer cortex, making it useless for food, and 

 admitting secondary pests, such as slugs and wood-lice. Discoloration 

 of the root follows, with wilting and yellowing of the foliage and 

 sometimes a reddening of the tops. Besides carrots, parsnips, celery, 

 turnips and parsley are attacked. An undescribed Braconid of the 

 genus Dacnusa is parasitic on the pupa of P. roae. 

 (5155) D 



