ENTOMOLOGY

THE LIFE HISTORY OF HUMAN LICE 309arc preferred. However, in case of necessity, the lice can and will ovipositon smooth materials such as silk and sateen. It has been suggested thatinfestation could be greatly reduced and even remedied entirely by wearingfor one to twent}-four hours a broad band of felt or rough wool underthe clothes, with the idea that lice would collect on this, and they andtheir eggs could then be destroyed by burning. But the preference oflice for such material and the difference between this and the uniform isnot marked enough to make it really effective.In practical control work the question is likely to arise as to howlong disc;arded but untreated clothing will remain infective. The answerto this, of course, depends. on how long lice can live without foodand hOlY long it takes for all the eggs to hatch. Experiments showthat lice can live without food from two to three days at 55° C., threedays at 50° C., three to five days at !!2° C., and about seven days at10 0 C. The lice cannot live long without food unless at ineffective temperatures,the longest period recorded being ten days at 5° C.(41 0 F.). The longest record of fed adults is 46 days for a femalerecorded by Bacot. One male lived 5!! days and fertilized eighteen females.As stated above, eggs will hatch in sixteen days at !!5° C., butbelow !!!!O C. they usually do not hatch. How long a period of low temperaturesthey can endure, and still hatch when the temperature is againraised, is not known beyond a statement by Nuttall that he delayed hatchingto 55 days by low temperatures. Certainly the safest plan would beto allow 30 to 40 days of cool weather or-two weeks of hot weather forall the eggs in discarded clothing to hatch.There are three larval stages, or possibly we may