Formicidae 



509 



nest and a water moat around it to prevent the escape of the ants, has 

 proven very successful (Fig. 82). 



A water-tight pan, 12" x 12" x 2" deep, is used. In the center is 

 placed a water-tight enclosure, 6" x 6" x 2%" or 3" deep, in which moist, 

 black soil is provided for nest build- 

 ing. Over each edge of this center 

 nest section is hung a strip of tin, 

 bent at an angle and reaching 

 down to the surface of the water. 

 This bent strip prevents the ants 

 from drowning as they rush precip- 

 itately over the edge of the nest to 

 attack the disturber whenever the 

 cover is lifted or the nest is otherwise 

 disturbed. It also provides easy 

 access to the water and might even 

 be used for feeding. The surrounding 

 space, 3 inches in width, is kept filled 

 with water to prevent the escape of 

 the ants. The nest is kept covered 

 with a piece of tin or other opaque 

 material, or may be covered with a 

 glass plate if closer observation is de- 

 sired; the cover prevents too rapid 

 evaporation from the soil, which must be kept moist at all times. 



Feeding may be done in small tin covers, or other small, shallow re- 

 ceptacles, placed in the nest on the surface of the soil. 



The accumulating excavated soil in the moat may be flushed out 

 with water from a rubber tube attached to a faucet. A small hole in 

 each corner of the moat as close to the bottom as possible, is con- 

 venient for cleaning purposes. The holes may be kept stoppered with 

 small corks when the moat is not being cleaned. The water in the moat 

 must be changed from time to time, as a thick film soon covers it and 

 this may become strong enough to allow the ants to escape by walking 

 on it. 



Observation nest. Several observation nests are available at bio- 

 logical supply houses. These are often elaborate and more expensive 

 than necessary. A simple, inexpensive way to observe ants is to estab- 

 lish colonies in glass finger bowls. The ants are confined to the bowl 

 by a glass plate over the top of the bowl. Moist filter paper or blotting 

 paper covers the bottom. An extra folded piece of filter paper provides 

 a place for hiding and for storage of the young. 



When feeding the ants or cleaning these nests, the finger bowl is 



Fig. 82.— Diagram of stock nest for 

 Formica ulkei in the laboratory. 



