Reactions and Pkoducts in Inteespecific Crosses 147 



accustomed for generations, and their progeny and testing thereof was all done 

 under the same conditions, so that the conditions of the medium play little or 

 no part in the history of this combination. 



On July 18, 1907, a pedigreed L. decemlineata (F^^ female) was mated with 

 a pedigreed F,, male L. diversa. Both were young, freshly emerged, and typical 

 of their respective lines. These gave progeny that in the larval stages were in 

 all respects precisely that of the L. decemlineata type ; from these there emerged 

 on September 18, 11 male and 8 female adults that were all of the decemlineata 

 type. On July 12, 1908, a precisely similar mating was made that gave progeny 

 from which were obtained on September 16, 22 males and 25 females. In this 

 series all the juvenile stages in all respects were indistinguishable from decem- 

 lineata, and the adults were also fully of the female parent type. In both of the 

 series they were the only pairs out of 20 in the July 1907 mating, and out of 

 32 in the July 1908 series that gave progeny from which adults were obtained. 



In making these crosses it is necessary to have in the cage two different food- 

 plants — that of each parent ; otherwise the chances are entirely against obtain- 

 ing any reaction from the mating. Under these conditions the female decem- 

 lineata will deposit the eggs irregularly on both of the plants, with an average 

 larger number on the normal food than on the other. These eggs, when they 

 hatch, give larvse that do not feed on the succulent type with any degree of 

 success, and in those larvae that are on the potato the mortality is, if left thereon, 

 always 100 per cent. If on the woody type, or transferred thereto, they thrive 

 well and in the two series there were 75 larvae in the 1907 set and 82 in the 1908 

 set, all healthy, well nourished, and the progeny that came from them also were 

 fine, large specimens, and like the larvas would only feed upon the woody type 

 of food-plant. In the length of ontogeny F^ showed the rate characteristic of 

 the dvversa parent, which was about 60 days, whereas the same value in the 

 decemlineata parent in the strain used was 38 to 40 days. 



These Fj hybrids were clearly composites, showing in gross bodily qualities 

 entire dominance of the female parent's characteristics ; in rates of growth, and 

 in food preferences the strict limitations of the male parent. In other attributes 

 difiScult of statement, these individuals showed the type of reaction now of the 

 male, at other times of the female parent, but in all respects uniformly so, the 

 entire population composed of the two fraternities being strikingly uniform. 

 In both cultures the Fj fraternity entered into hibernation by the end of Sep- 

 tember, remaining until the following March, when they emerged, and were 

 tried first upon potato, which was not touched, then put upon Solanum chriso- 

 trichwm, which was at once eaten, and by April 1 reproductive activities had 

 begun. In April 1908, I mated 7 pairs of the first series that arose in 1907, 

 and these bred at once, all 7 pairs giving progeny, which emerged between 

 June 5 and 15, having an average ontogeny of 61 days. The record from the 

 pairs is shown in table 18. 



The larvse were without exception all pure decemlineata type, like the 

 female-parent stock, and the adults were all like the F^ fraternity, with no trace 

 of separation into types. Biometric tests, made of fraternities from matings 

 A and D, gave no indication of multimodal conditions, the findings in the 

 measurement of the form-index showing a monomodal polygon that was in all 

 respects precisely that of the pure decemlineata stock in position and distribu- 

 tion of frequencies. 



