76 CARNEGIE INSTITUTIOX OF WASHINGTON. 



In previous Year Books there have been noted the modifications of 

 the antennaj in L. signalicollis, which was produced in experiments at 

 Chicago as the result of desert conditions. This year in one of the cul- 

 tures of our mutant forms we found one female with antennse having 

 the same type of antennal modification. She is now mated with a 

 normal male and already a large progeny is assured. Whether the 

 change, which is a profound one in an invariable racial character, is 

 gametic or not is not yet known, but it is of extreme interest that this 

 same type of change in the same organ should arise upon two unlike 

 experimental stocks as the result of the impact of essentially the same 

 set of conditions in the medium. That the changes are the direct 

 result of the action of the conditions in a desert complex there can be 

 no justifiable doubt. Of the thousands of specimens of this material 

 that have passed through my hands, in experiment and from nature, 

 no examples of this conspicuous change have been seen, and in the 

 materials stored in the museums in America and Europe there is not 

 to my knowledge a single example of this iy^Q of antennal character 

 known in Leptinotarsa or in any other species of the phytophagous 

 Coleoptera. 



In the reports for 1912 and 1913, progress was noted in the series of 

 experiments concerning the water relations of pure cultures of L. decem- 

 lineata. During the past year these experiments have been continued 

 and expanded. Cultures that have been at Tucson only four genera- 

 tions failed to pass the winter conditions of 1913-1914 at Chicago, and 

 were entirely eliminated, as were those that had been at Tucson under 

 desert conditions for longer periods. It was found, however, that a 

 culture that was sent to Chicago, and reproduced there, showed the 

 beginning of a reversal of the process, three individuals emerging out of 

 nearly 700 that went into hibernation, and we now have their progeny 

 at Chicago, which will be tested concerning their resistance during the 

 coming winter. Next year we shall be in a position to make prelimi- 

 nary tests to determine, if possible, the nature of this change in these 

 materials when there will be available materials that range from freshly 

 introduced stock to those that have been at Tucson for 15 generations. 



All of these stocks of L. decemlineata are showing marked gradual 

 movements towards an albinic condition and other indications that 

 the pressure of desert environment is beginning to have an action that 

 may soon show itself in other changes. 



The introduction of species from the rain-forests or from the monsoon 

 climate conditions have thus far proved failures, as none have been 

 able to persist for more than a generation. The pure stocks are far 

 more delicate and do not seem to be able to exist at all, but when two 

 are crossed and the Fi hybrids are introduced, these seem in most 

 experiments to be able to survive and reproduce. During the winter 



