Oct. 22, iQji Hopkins Host-Selection Principle 217 



HYPERPI/ATYS MACUIvATUS. EXPERIMENTS XXVI, XXVIII, AND XXIX 



Hyperplatys maculatus Hald. occurs throughout the eastern United 

 States and west through the Rocky Mountain region. Two very similar 

 species have been described, H. maculatus Hald. and H. aspersus Say, 

 but the distinction is not drawn here, as each has many variations in 

 color and maculation. It feeds on a great variety of hardwood deciduous 

 trees. Probably any wood is attacked, provided it is in the proper 

 condition for infestation. Smaller twigs and branches are usually pre- 

 ferred. Those that have died during the fall and lain on the ground so 

 that a certain amount of fermentation has taken place in the bark give 

 the optimum condition. 



The larvae feed entirely beneath or in the bark, only entering the sap- 

 wood to make a very shallow pupal cell. Adults fly in the early summer, 

 late May, and early June. Two distinct variations occur in the length of 

 the seasonal history. One form takes an entire year to complete the 

 development, only one generation appearing each year. Another ma- 

 tures from one-half to three-fourths of the brood in August and Sep- 

 tember, the adults emerging and infesting new wood. This may be a 

 basis on which to separate the two confused species. Four host strains 

 have been experimented with, chestnut (Castanea dentata), gooseberry 

 (Ribes), dogwood (Cornus florida Linn.), and yellow poplar (Liriodendron 

 tulipifera lyinn.). 



HYPERPLATYS MACULATUS, LIRIODENDRON HOST STRAIN. EXPERIMENT XXVIII 



The colony was started by collecting infested tulip branches in No- 

 vember, 1916, at Falls Church, Va. The following June adults emerged 

 and were isolated in a cage containing yellow poplar, maple, dogwood, 

 chestnut, and gooseberry cut in the fall of 1916. The original host, 

 yellow poplar, was well infested, and a few larvae were found in goose- 

 berry, but no other woods were attacked. In 1918, 1919, and 1920 the 

 colony was continued in yellow poplar; the selection was not repeated. 



Only one generation of this form occurs each year. 



Castanea. Experiment XXVIII ^ — ^June 4, 1917, ten adults from 

 yellow poplar were caged on chestnut cut in November, 1916. A very 

 good infestation was secured, forty-five adults emerging in 1918. Eight 

 of these adults were isolated in a cage containing yellow poplar and 

 chestnut cut in November, 191 7. 



Examination in August showed the yellow poplar to be heavily 

 infested, while no larvae were present in the chestnut. 



June I, 1 919, two pairs from yellow poplar were isolated on chestnut, 

 and in 1920 thirty-six adults emerged. Ten were caged on optimum 

 cuts of chestnut, and the yellow poplar was heavily infested. 



HYPERPLATYS MACULATUS, RIBES HOST STRAIN. EXPERIMENT XXVI 



This colony was started in December, 191 5, with infested gooseberry 

 stems sent to Falls Church, Va., from Colorado Springs, Colo., by G. 



