444 Phylum Arthropoda 



PESTS 



Wild flies, and their immediate descendants, sometimes have tangled 

 whitish masses of soil nematodes about the bases of their legs and wings; 

 these impede their movements and lead to death. This condition is, 

 however, too rare to be a serious difficulty. There are also hymenop- 

 teran parasites and fungi of the Empusa group that attack wild Droso- 

 phila; but these have never been encountered as laboratory pests. 



There are only two serious laboratory enemies to be dealt with: 

 molds and tyroglyphid mites. The remedy for molds is to prevent in- 

 fection, by sterilizing bottles thoroughly, sterilizing or replacing cotton 

 plugs, and watching the yeast supply. The infection from spores at- 

 tached to the parent flies themselves may be decreased by repeated 

 transfers (at one or two day intervals) to new culture bottles. In gen- 

 eral, molds are not serious pests for vigorous strains of flies kept at opti- 

 mum temperatures on satisfactory media, since under these conditions 

 the activity of the larvae keeps the hyphae from developing many 

 spores. There is a German proprietary substance sold under the name 

 of "Nipagin" that is stated to inhibit mold growth without harming 

 yeasts or flies. Several workers have reported success with its use. 

 Parker ("Drosophila Information Service" 4) reports more satisfactory 

 control with less expense from the use of "Moldex-A," obtainable from 

 the Glyco Products Company, 949 Broadway, New York, New York. 



The tyroglyphid mite (genus and species not determined) that makes 

 trouble is a more serious enemy. The adults and early nymphal stages 

 feed in the more moist parts of the culture bottle ; so far as known they 

 do no damage. There is however a facultative last nymphal stage, known 

 as the hypopus, that does not feed and wanders to the drier parts of the 

 bottle, often becoming attached to the adult flies. Such enormous num- 

 bers often cling to a single fly that the latter becomes scarcely able to 

 move and soon dies. The hypopi also crawl out of the bottle and may 

 travel many feet and into a fresh bottle. Sometimes whole laboratories 

 seem to be over-run with them. The best remedy is prevention; at the 

 first sign of their presence the infected bottle should be quarantined — 

 discarded and quickly sterilized if possible. Carbon tetrachloride should 

 be poured into all suspected bottles as soon as they are discarded. 

 Painting shelves and outside of bottles with kerosene is helpful. Since 

 wild flies in the room may be carriers, they should be destroyed as far 

 as possible. Lightly infected individuals, if it is important to keep them, 

 may be "deloused" under the microscope, or repeatedly transferred to 

 fresh vials, when the hypopi will gradually drop off of their own accord. 

 In badly infected laboratories it may be necessary to keep the culture 

 bottles on a water-table, in a solution of creosote. Soapy water has 

 been tried for this purpose ; it is apparently effective. 



