UNIT-CHARACTERS OF INSECTS 155 



color. Presence of pigments in the larval skin is dominant 

 over uncolored skin. Various patterns of the larval pigmen- 

 tation (spotting, striping, etc.) are dominant over 'their ab- 

 sence. Reddish-brown color of the larva is recessive to black. 

 The possession of knob-like outgrowths of the larval skin is 

 dominant over smooth skin. 



TABLE 20 



Unit-Characters of Silkworms 



1. Egg Characters, all Maternal in Origin 

 Duminant Recessive 



(1) Univoltine. Bivoltine. 



(2) Eggs oval. Eggs spindle-shape. 



(3) Eggs normal slate color. Eggs light brown or gray. 



2. Characters of the Larva or the Cocoon, of Biparental Origin 



(1) Tri-moulting. Tetra-moulting. 



(2) Blood (and silk) yellow.i Blood (and silk) white. 



(3) Silk white (European races) . Silk yellow. 



(4) Larval skin pigmented. Larval skin unpigmented. 



(5) Larva spotted or striped. Larva not spotted or striped. 



(6) Larva black. Larva reddish brown. 



(7) Larval skin with knob-like Larva not knobby. 



outgrowths. 



TMiite cocoon-color (silk) has been foimd in some races to 

 be a recessive character and in others to be dominant. The 

 two kinds of white have been shown to be genetically distinct. 

 One is probably a loss variation like albinism in rodents, the 

 other a white variation due to inhibition of color, like some 

 forms of white spotting in mammals. Certain variations in 

 the color and shape of the egg have been found to Mendelize, 

 but with the same complication as in the variation from 

 univoltinism to bivoltinism. Egg characters being deter- 

 mined entirely by the mother, the influence of the father does 

 not show in the Fi generation. Which of the contrasted 

 characters is dominant does not become evident until eggs 



' LMa has recently shown that yellow color of the blood is due to a single domi- 

 nant factor but that the silk will also be yellow only when a second and independent 

 factor is also present. When this second factor is lacking, white silk will appear to 

 be dominant over yellow silk, even though the blood is yellow. 



