February, '15] 



DAVIS: STUDYING UNDERGROUND INSECTS 



137 



which has been sifted to make certain it is free from insects, and seeded 

 with a mixture of timothy and blue grass. Pieces of old corn stalks 

 are usually included since the young grubs {Lachno sterna, Cyclocephala, 

 Anomola, etc.) like to feed on decaying vegetation, and for grubs which 

 are partially or wholly scavengers manure is added. Pots thus pre- 

 pared are buried in the soil almost to their tops, and covered with 

 cyUnder-shaped tops as in the accompanying illustration (PL 3, fig. 

 4). Beetles, preferably pairs collected in copula are introduced and 

 in the case of leaf-eating beetles, foliage is supplied as needed. It is 

 necessary at various times to reseed or plant corn in the cages and, 

 above all, it is essential to watch them and water as required, for they 

 do not hold the moisture as does soil under natural conditions. It is 

 equall}^ necessary to water the wire cloth cylinder cages during the 

 warmer and drier parts of the year for they do not retain the moisture 

 any better, if as well, as the pots. During the winter, covers are 

 removed and the pots covered with straw and this with strawy manure 

 to a depth of one foot, which will gradually pack down to a compara- 

 tively thin layer (PI. 5, fig. 9). Since the grubs do not, in flower pot 

 cages, have an opportunity to go down to their normal depth for hiber- 

 nation, this precaution is desirable and does not materially affect the 

 conditions as found in nature. Cages such as these, which are used 

 to obtain the total life-cycle, are examined for grubs only once or twice 

 in a year in order to obtain specimens of the different aged grubs, and 

 duplicate cages are invariably left undisturbed until the summer the 

 beetles are to appear. 



For obtaining eggs and records of individual pairs, 12-inch three- 

 quarter or standard size pots filled with finely sifted soil are used. 

 They are covered with w^re screen tops within which single pairs are 

 placed. The soil in these cages is not seeded nor are the pots sunk in 

 the soil, but foliage is suppHed as needed and a record kept of the 

 amount of each kind of foliage eaten by the beetles. The pots are 

 kept in .a shaded or partially shaded location and every day or every 

 few days the cages are sifted, using a 16-mesh riddle. If the soil 

 contains the proper moisture content, the small balls of earth contain- 

 ing the eggs will remain intact, the loose soil sifting through. ^ The 

 balls of earth are broken in half and the part containing the egg or 

 eggs placed in boxes of soil, or small cavities, resembling the original 

 egg cavity, are made in the boxes of earth and the egg placed therein, 

 a damp camel's hair brush being used to dampen the eggs. The earth 

 in the egg boxes is moistened as necessary and kept in a cool place 

 comparable with natural soil conditions. We have also used shallow 



1 This is the case with Lachnosterna, Allorhina, Euphoria, Diplotaxis, etc., but a 

 few beetles do not make such a compact ball and the eggs appear in the riddle free. 



