184 Annals Entomological Society of America [Vol. XV, 



August 12, the heads were examined for seed, and the 11 

 heads present, with 293 florets, yielded 90 seeds, or 30 per cent. 



These observations and experiments are simple but con- 

 clusive. They prove that Tetralonia dilecta poUenizes red 

 clover to an important extent in the latter part of May and in 

 June (in central Illinois), and that Melissodes himacidata also is 

 an efficient pollenizer of plants that bloom during July. 



The present summary is simply for the purpose of placing 

 these facts on record; a detailed account of further studies 

 being left for a future article. 



ARE THERE TWO SPECIES OF THE OYSTER-SHELL 



SCALE?* 



Grace H. Griswold. 



The Oyster-shell Scale (Lepidosaphes ulmi, L.) has been 

 a subject of study on the part of the writer since the spring of 

 1919. During the summer of that year, observations were 

 made on the biological development of this insect on lilac. 

 In the fall, while making egg counts from various host plants, 

 it was noticed that the scales formed on apple trees seemed to 

 differ in appearance from those on lilac and some of the other 

 ornamental shrubs and trees. It was therefore determined 

 to make a comparative study of the biological development 

 of the insect on apple and lilac the following summer. 



Studies of this insect have resulted in the finding of three 

 distinct differences between what may be called the apple 

 and lilac forms: 



1. Differences in the appearance of the scales. 



2. Differences in biological development. 



3. Differences in morphological characters. 



* Contribution from the Entomological Laboratory, Cornell University, 

 Ithaca, N. Y. 



