256 



The Journal of Heredity 



THE INSECTS ARE STUDIED WITH A 

 BINOCULAR 



Adults of moths or wasps arc etherized for exannnation. 

 If it is desired to study the ovipositing wasps or to count 

 their eggs the paralyzed caterpillars are placed upon a piece 

 of glass which is set about three-quarters of an inch above a 

 mirror. IJy focusing either upon the insects directly or upon 

 the image, upper or lower sides may be observed at will. 

 (Fig. 11.) 



For individual niatings frcsJily 

 emerged pairs are set in tin boxes with 

 tightly fitting covers. A type of cylin- 

 drical slip co\er can, made by Mason 

 Manufacturing Co., Pro\ idence, R. I., 

 having a diameter of se\en and one- 

 half inches and depth of four inclies 

 has been foinid to be of con\enient 

 size and satisfactory for the purpose. 

 The can, containing a little cereal and 

 the isolated pair, is set away on a shelf. 

 No food for the adults is necessary. A 

 warm temperature, 27° to .^0° (\, gives 

 best results, l)Ut Inmiidilx- must be 

 fairly high or yoimg lar\ae will not 

 develop. During the winter, in pres- 

 ence of artificial heat, it is often 



necessary to place dishes of 

 water in cupboard where tins 

 are set. 



Contamination of the cul- 

 ture is prevented by toasting 

 or autoclaving the cereal and 

 l)\' placing a little vaseline in 

 1 lie crevice formed by the 

 ^(^■am at the cover. Beetles, 

 mites, bacterial and protozo- 

 an diseases may otherwise be 

 introduced, as well as unde- 

 -Ired caterpillars or moth 



The moths scatter their 

 eggs over the cereal and these 

 hatch in approximately a 

 week, the time varying ac- 

 cording to temperature. The 

 young larvae spin webs at- 

 taching particles of cereal 

 together. After tw^o or three 

 weeks, an inspection should 

 reveal webbiness of the cereal, 

 denoting successful pairing 

 and fertility. More cereal 

 should then be added and the 

 box set away again. If tem- 

 perature is high larvae will 

 attain full size in four weeks 

 from time of isolating the 

 parental pair. Pupae are 

 then formed in silken tubes. 

 The entire period from egg 

 laying to eclosion may be 

 reduced to five weeks, but 

 usually six weeks are required 

 for a generation in summer 

 weather. Eclosions begin at 

 tJie end of this time and moths will con- 

 tinue to emerge for three or four weeks 

 or longer if culture is crowded when 

 there will be many laggards. 



There seeins to be a diurnal cycle of 

 some sort in eclosion. Many more 

 moths emerge in the latter part of the 

 afternoon and in the evening than 

 during the rest of the day. It is there- 

 fore advisable to be on the watch at 

 this time if virgin females are desired 

 for mating. Copulation takes place as 

 soon as wings are dry, so that the 

 virginity of any female is never certain 

 unless wings are soft or imless there are 

 no males present. 



