J. W. H. Harrison 255 



noteworthy fact that forcing operations in the genus Oporahia are futile, 

 and the possibility of crossing the two forms becomes very remote, but 

 still not absolutely excluded. Precocious individuals of 0. autumnata 

 and belated representatives of 0. filigrammaria occasionally overlap 

 and therefore^ if of opposite sexes, can be mated. Now this acts rather 

 curiously in the matter of reciprocal crosses. Tn all of the species in 

 the genus the males precede the females, with the necessary result that 

 such overlapping specimens usually include female filigrammaria and 

 male autumnata, and that combination is the one usually secured. 

 However, in excessively rare instances, one can cage up filigrammaria 

 males and phenomenally early autumnata, females as I did, for the second 

 time in my long continued work on the genus, in September 1918. 



When the opposite sexes of the two forms are caged together so close 

 are their pairing and physiological affinities that no matter how small 

 the cage they pair the same evening; the pairing, as is usual in the 

 genus, lasts for a few minutes. Eggs are deposited the following night 

 and three days later betray their fertility by changing from green to 

 pink. The percentage of fertile eggs does not deviate from that of the 

 pure species, and the same holds true of their successful hibernation 

 and subsequent hatching in spring. 



The latter operation commences between the periods of the early 

 hatching filigram,maria and the later autumnata but always inclining 

 distinctly towards the latter. This curious fact is important inasmuch 

 as it is apparent that the male parent is exhibiting the greater influence, 

 not, as Toyama^ found in the silk moth, Bomhyx mori, the female. 

 Opposed as this observation is to Toyama's results, nevertheless it agrees 

 completely with those in my reciprocal crosses between univoltine and 

 bivoltine races of Selenia bilunaria, in which the male habit determined 

 the fate of the ova. Precise dates of emergence are of little value, so 

 greatly do they oscillate from year to year according to the forwardness 

 of the season; in 1918, for example, 0. filigrammaria hatched on February 

 28th, autumnata on March 18th and the hybrid ova on March 14th ; in con- 

 trast with this today, March 15th, 1919, not a single ovum of any of the 

 species or hybrids evinces the slightest sign of movement. 



As they hatched the larvae were supplied with hawthorn {Crataegus 

 oxyacantha); this they accepted and fed on with such avidity that they 

 were in the ground early in April, that is, earlier than autumnata and 



1 Toyama, "On the Hybridology of the Silk-worm," Kept. Seric. Ass. Japan (1906). 

 Toyama, "On Certain Characters of the Silk-worm which are apparently non-Mendelian," 

 Biol. Centrbl. Vol. xxxii. (1912). 



