148 Trans. Acad. Sci. of St. Louis 
nection with the rhythmie periodicity of each species, leads one 
into entanglements which are not easily solved. 
It would be best, therefore, before giving details of the ex- 
periments, to give a brief resume of the work that has been done 
on the rhythmic periodicity of organisms. 
‘Living matter is rhythmic; it is always doing something at 
intervals; these intervals often seem to have no relation to out- 
side influences, like breathing or the recurrent beats of the 
heart, but in many cases the intervals of the acts correspond 
with the cosmic changes. Night and day control sleep; the tides 
have a marked influence on the habits of many of the shore liv- 
ing invertebrates, and so ingrained are these periodic habits that 
they are retained even when the animal showing them is re- 
moved inland and kept in a perfectly still aquarium. Summer 
and winter, seed time and harvest play perhaps the greatest 
role in this rhythm. One has only to think of the breeding 
habits of most animals, and the annual appearance and disap- 
pearance of the foliage of deciduous trees to recognize this.’’ 
So says Arthur E. Shipley, in his introductory chapter of 
‘‘Life.’’ In a later chapter on Rhythm he interestingly touches 
upon various kinds and types of rhythms in both the animal 
and the plant world. He writes on the rhythm of cells, rhythm 
of parts of cells, rhythm in tissues, rhythm in organs, rhythm 
in organisms, and rhythm in communities. 
Our general interest in the present work is rhythm in insects, 
and especially in moths. In Shipley’s work there is no mention 
of this for moths. Bouvier has a chapter in his ‘‘Psychie Life 
of Insects,’’ entitled ‘‘Vital Rhythms and Organie Memory,’’ 
and while there is little mention of night and day activities of 
moths, he does discuss the work that has been done on rhythms 
of insects and other invertebrates from the time of Reaumur to 
the present day workers. 
Charles Elton, in his Animal Ecology, tells us that many 
animals in a community never meet, because of the fact that 
they become active at different times. This is because the 
environment is subjected to a number of rhythmical changes 
which result in corresponding variations in the nature of the 
animal communities at different times. There is a day and 
night rhythm which affects both free living animals and some 
parasites. This rhythm may be of practical importance, and 18 
