Medric-Louis-Elie Moreau de Saint-Mery, a French-refugee in America between 1793 and 1798, wrote this account of Philadelphia: Another veritable torture during Philadelphia's hot season is the innumerable flies which constantly light on the face and hands, stinging everywhere and turning everything black because of the filth they leave wherever they light. Rooms must be kept closed unless one wishes to be tormented in his bed at the break of day, and this need of keeping everything shut makes the heat of the night even more unbearable and sleep more difficult.

And so the heat of the day makes one long for bedtime because of weariness, and a single fly which has gained entrance to your room in spite of all precautions drives you from your bed.

Isay one fly because many among them are a sort of blisterfly, and once they have attacked you, you can...