DEPARTMUNT OF EXrERI MENTAL EVOLUTION. 79 



inasmuch as it was probably the only self-fertilized lata under cultivation in 

 America at that time. 



Two points of especial interest have been brought out by these preliminary 

 studies : First, the large number of chromosomes found in pure-bred O. 

 gigas arising as a mutant from O. lamarckiana {laniarckiana, 14; gigas, 28), 

 Second, the strong indication of variation in the number of chromosomes of 

 the somatic cells of each species studied. A large number of pure-bred 

 Oenothera seedlings are now growing in the greenhouse for the study of 

 chromosome variation during the ensuing year. 



Variation and Heredity in CoccineUids. — Roszvell H. Johnson. 



The removal, in March, of my breeding experiments with coccinellids from 

 an inadequately heated and lighted room in the main building to the newly 

 completed vivarium was sorely needed. Many new pedigrees were started 

 at that time from the variations found in a large lot of living beetles taken 

 from a hibernating mass on a hill-top in eastern Washington. These were 

 successfully bred until August, when excessive humidity caused many deaths. 

 It may be possible to avoid this another season. 



While the increased facilities for providing food make it possible to raise 

 many more beetles, the labor of the daily individual feeding of any consider- 

 able number of these carnivorous insects becomes a serious item. This 

 feature, together with the difficulty of keeping the aphid supply at all times 

 adequate, will restrict breeding operations with the carnivorous coccinellids, 

 hereafter, mainly to the testing and interpretation of the variations found. 

 Studies on heredity involving m.any consecutive generations will therefore be 

 carried on with the less interesting leaf-eating coccinellid genus Bpilachna 

 and the leaf-eating spotted chrysomelid genus Chelymorpha. 



I published in the Entomological News for May, 1907, an article entitled 

 "Economic notes on aphids and coccinellids." Besides various notes, this 

 contained a list of aphids on previously unrecorded hosts, found in seeking 

 available food for the beetles. This data is of value to economic entomolo- 

 gists, and was separately printed. The principal results up to August, 1907, 

 were briefly presented in a paper on "Heredity in color pattern in coccinellid 

 beetles" at the Seventh International Zoological Congress. The main points 

 of this paper follow : 



Hippodaniia convergens is found throughout the United States. In various 

 regions, however, it is accompanied by varieties characterized by decided dif- 

 ferences in elytral coloration. For example, in the lower altitudes of Cali- 

 fornia the associated variety has spotless elytra. The species and its variety 

 are in direct competition and regularly interbreed with little or no assortative 

 mating, yet by alternative inheritance the variety resists assimilation and 

 maintains its identity. In this case imperfection of dominance leaves a trail 

 of individuals with spots impaired, yet the segregation in the second genera- 

 tion saves the variety. Without the direct evidence of witnessing the origin 

 of these forms by mutation, we may nevertheless conclude that evolution is 

 taking place here by that process. A further consequence is that these strik- 

 ing differences in color pattern are without selective values, else the varieties 

 would have been eliminated or have replaced the parent species. Knowing 

 these things, the otherwise extraordinary result that some H. qninquesignata 

 females from the mountains gave me young H.lecontei, as well as H. qnin- 

 quesignata, can be understood. I find that H. qninquesignata and H. leeontei 

 have similar ranges and often interbreed. Intergrades in nature and in the 



