104 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. lOfl 



mouth pint canning jars, jars measuring 140 mm. by 135 mm., 

 weighing bottles, and 4-ounce amber jars were used with bottoms 

 intact. The plaster-charcoal mixture was poured into these, 

 forming a base which varied in thickness from 5 mm. in the 

 weighing bottles to 35 mm. in the larger containers. Some wide- 

 mouth jars were completely lined with the mixture. One weigh- 

 ing bottle and one wide-mouth pint jar were lined with moist 

 cellulose wadding. Some containers were stoppered with cotton 

 plugs, others with solid lids. The plaster-charcoal was kept moist 

 with distilled water to maintain high humidity within the cul- 

 tures. 



Some cultures were established in containers without the addi- 

 tion of media or substrates for the mites. In most cultures some 

 material through which the mites could move was added. Screened 

 soil from forest and open field was used. In earlier cultures a film 

 of animal charcoal was placed on the plaster-charcoal base, and 

 the soil was poured over this. Mixtures of washed sand and soil 

 and stratified sand and soil were tried. Depths of these media 

 varied from 2 or 3 mm. to 50 mm. Some were autoclaved ; others 

 were not. Decayed wood from an oak log, leaf mold, and humus 

 were used without autoclaving. Vermiculite was used alone or 

 mixed in equal parts by volume with humus or the debris collected 

 under the bark of a decaying tree. 



A variety of foods were tried in an effort to find a kind that 

 the free-living stages would accept. The foods tried were pieces 

 of white potato, pieces of apple, moist fiber from a Neotoma 

 floridana (Ord) nest, mouse feces, ground beef, beef liver, flying 

 squirrel flesh, gelatin, ground beef in gelatin, beef liver in gelatin, 

 and pieces of earthworm. Ant larvae, bisected ant pupae, and 

 decapitated Onychiurus sp. and termites were offered. A female 

 Pediculoides mite producing young was placed in one culture. 

 Other offerings were Aedes eggs, Aedes eggs sterilized in White's 

 solution (Trager, 1937), Aedes eggs ruptured with a needle, 

 dissected Aedes eggs and ovaries, Culex eggs, ruptured Culex 

 eggs, large bug eggs punctured with a needle, dissected grass- 

 hopper eggs, spider eggs, eggs dissected from a small fly, dis- 

 sected soldier beetle eggs, dissected ant ovary, blowfly eggs, 

 crushed blowfly eggs, blowfly maggots hatched in the culture, 

 and May fly eggs. Living Onychhu-us sp. and other living un-' 

 identified apterous insects in variety were placed in cultures., 

 Fresh forest soil with all its contained organisms was used.. 

 Euschongastia nymphs were placed in Trombicula alfreddugesii 



