Bombycidae 367 



If the eggs are at all crowded, dispersion of the larvae as widely as 

 possible over the food-plant must be undertaken after the first molt; 

 later, when the foliage becomes sparse or covered with aphids, the larvae 

 must be transferred to a fresh pot of clover. 



Even though the caterpillars are sedentary, as in Colias, the pots 

 carrying a culture must be covered with cages, or, better, with a single 

 large cage extending over all the pots of the culture. Such a cage may be 

 made of a wooden frame covered internally with fine black netting (white 

 is too opaque) and accurately fitting the surface of the table. This 

 should be as flat as possible and preferably of cement, so that it may be 

 washed frequently with a hose. 



Most caterpillars are subject to diseases corresponding to flacherie 

 and pebrine of the silkworm. If a green, naked caterpillar is off-color or 

 slightly pale, it should immediately be isolated, for "polyhedral disease," 

 resembling flacherie, is highly contagious, and the leaves near the sick 

 caterpillar soon become contaminated. If the disease does not kill the 

 larva, it slows up development, the suspended caterpillar later droops and 

 dies, or the pupa turns black and purulent. 



The healthy full grown larvae usually leave the plants and pupate on 

 the walls of the cage, though some will be suspended on the plants. The 

 cage, with all the pupae, may now be removed to any laboratory table, 

 preferably in a cool, dark room where the emerging butterflies will not 

 mate. 



On emergence, it is desirable to mark each one with a letter designating 

 the brood and a number indicating the individual. This may be done 

 with a stub pen and India ink diluted with 50% alcohol to make it flow 

 freely. I regularly mark the ventral side of the right hind wing. The 

 date of emergence having been recorded, the butterfly's age is always 

 accurately known. The males and females of any brood are now kept in 

 separate cages in a cool, dark room with adequate humidity. Once or 

 twice a day they should be brought into the sunlight and allowed to feed 

 on moistened flowers. 



Mating is easily brought about by placing a few individuals of each sex 

 together in a cage of the dimensions mentioned or others 15" x 15" x 15". 

 The cage is set upon a square wooden tray (16" x 16" inside), with sides 

 about 2" high to prevent the escape of flying butterflies when the edge of 

 the cage is lifted. The cage upon its tray is then put into the sunlight; 

 pairs are taken out and isolated as soon as they form. Mating lasts from 

 a half hour to several hours, usually one or two. The same male may be 

 mated again the next day with a different female. This is important 

 in testing a male's genetic make-up. Females known to be impregnated 

 are thus ready to set over potted food plants, or are kept in reserve for 

 use if others prove sterile. A female requires only a single mating. 



