E.L. Karlstrom Bufo collecting, etc. April 5 making a grip on a forelimb if possible. Some grass may help to insulate bulb from your hand. 2) Substratum. Bulb just below surface. 3) Air temperature. One inch above ground. Shade the bulb from direct sunlight and keep dry to avoid wet-bulb effect. Good trick is to prop thermometer in position, go on writing notes, until recording at equilibrium. 4) Water. Just below surface in shallows but note effect of different bottom composition. For reptiles an air temperature 3 feet above ground may show variation.