360 Phylum Arthropoda 



larger, mass-cultures should be divided up into smaller ones to reduce 

 the chances of disease epidemics. When the caterpillars are ready to 

 pupate it is especially important that they should not be too crowded. 



Lymantriidae* The nun moth (Lymantria monacha) and the gypsy 

 moth (L. dispar) overwinter in the egg stage. Eggs should be kept 

 through the winter in cotton plugged tubes held in a protected place out- 

 doors, as the eggs require a prolonged frost period. In the early spring, 

 the eggs are placed in an icebox and kept there until leaves of the food 

 plant become available. The eggs hatch very soon after being brought 

 to room temperature. Crataegus serves as food for both species of 

 Lymantria, although L. dispar will feed on oak, fruit trees, pine, and 

 larch, and L. monacha on beech and oak. Polyhedral virus diseases are 

 the chief difficulty to be overcome in the rearing of Lymantria. The 

 spread of these diseases is favored by overcrowding, excess heat and 

 moisture, and poor or insufficient nutriment. Breeding cages, before 

 being used for new cultures, should be washed with hot water or with 

 10% formalin in 50% alcohol, or some similar disinfectant. The pupae 

 of Lymantria, when several days old and sufficiently hard, are placed in 

 suitable combinations (depending on the purpose of the experiment) in 

 glass jars having blotting paper on the bottom and sides, and strips of 

 cardboard. The pupal stage lasts 2 to 3 weeks. Copulation and egg- 

 laying follow soon after emergence. The eggs are laid on the cardboard 

 strips, enabling subsequent convenient handling. 



Saturniidae. The moths of this family overwinter in a cocoon in the 

 pupal stage (with the exception of Anther aea yamamai which overwinters 

 in the egg stage). Some species (Saturnia pavonia, S. spini, and S. pyri) 

 require frost and should be kept outdoors during the winter, while other 

 species (of the Samia group) do not require frost and may be kept in 

 any cool place. [See also P. 00.] For purposes of mating, the cocoons 

 are placed in large breeding cages in the spring. Where special crosses 

 are to be made, and it is necessary to know the sex of the insects before 

 they emerge, the pupa may be removed from its cocoon, or better, the 

 cocoon may be opened just enough to reveal the posterior tip of the pupa. 

 Here in the genital region, the two sexes may be readily distinguished. 

 The moths mate soon after emergence and the female then begins laying 

 eggs. For most of the species the eggs hatch within 10 to 21 days of the 

 date of laying. European species are easily reared on Crataegus; An- 

 theraea on oak, apple, or hawthorn ; and Samia on Prunus or apple. Like 

 the Lymantriidae, Saturniidae larvae are susceptible to polyhedral dis- 

 eases, and the same prophylactic measures should be taken. 



♦Editor's Note: W. T. M. Forbes cautions that Lymantria is a very serious pest and 

 L dispar should be handled only in areas already infested. L. monacha should not be 

 handled at all in this country. M. E. D. 



