16 PROC. ENT. SOC. WASH., VOL. 20, NO. 1, JAN., 1918 



also claimed that there was evidence showing that four-fifths of 

 the newly formed protein in the chrysalids obtained its nitrogen 

 from the surrounding atmosphere. 20 These claims are most 

 unusual and the present writer is not aware that the original 

 claimant has received the support of other investigators. 



An interesting case of a single problem attracting the attention 

 of a number of investigators is shown by the references to papers 

 regarding fire flies and other light producing insects. These 

 papers began to appear, in the literature under discussion at 

 least, in 1911 and have continued to appear up to the present 

 time. The work referred to covers the manner in which light is 

 produced, the nature of the light, and that of the substances 

 concerned in its production. 21 



One of the main purposes in publishing this paper, and in 

 reviewing the work that has been done recently, in the field of 

 entomological chemistry, is to call attention to the fact that 

 this field is not overcrowded and that it affords many attractive 

 opportunities for study and experiment. It is very gratifying 

 to note that one of our most eminent scientists, Jacques Loeb, 

 during the last three years has been engaged in researches which 

 come within the scope of this review. In 1915 there appeared 

 an article by him on the simplest constituents required for growth 

 and the completion of the life cycle in an insect. 22 In 1916 another 

 was published on the salts required for the growth of insects 2 * 

 and, in 1917, a third in which he shows, in an investigation re- 

 garding the growth of certain flies, that yeast is a necessary food 

 for species of the genus Drosophila, and that, while these flies 

 may be kept alive on other foods, yeast is necessary for the pro- 

 duction of offspring. 24 



The very broad nature of the problem which Loeb is helping 

 to solve should be here noted. What is required in the food of 

 insects for their growth and reproduction? This is indeed a 

 difficult question and one which may never be completely an- 

 swered. It would seem however, judging by Loeb's success with 

 the lesser problem, in the case of Drosophila, that the necessary 

 food of a particular insect may in some cases be determined. 



In the case of the Lepidoptera, with which the writer is more 

 familiar, one finds at his disposal a vast amount of data with 

 regard to the food of a very great number of the species listed. 

 That these lists of foods, supposedly required, are not always 

 satisfactory is a matter of common knowledge. 



20 M. v. Linden, same as (19) b. above. 



21 Thirteen references may be found in Chemical Abstracts in volumes 

 5, 6, 7, 8, 9, 10, and 11. 



22 Loeb, Science, 41, 169-70 (1915). C. A. 9, 1944. 

 83 Loeb, J. Biol. Chem., 23, 431-34. C. A. 10, 354. 

 24 Loeb, J. Biol. Chem., 27, 309-12. C. A. 11, 851. 



