APPENDIX 525 



if the galls be wetted about once a week, (as by holding 

 them under the water tap, or by immersing them for a 

 minute in a bowl of clean water). Data given in chapter 

 I, (pages 44 and 45), will suffice for distinguishing the 

 midge larvae from their parasites (which are sure to be 

 numerous) and from the other occupants of the galls. (See 

 figure 36 on page 46.) 



A biological garden, while not absolutely required, is the 

 best possible equipment for the sort of a course this book 

 proposes. It need be a little more than a pond or a brook, 

 and a few little border plantings. There should be enough 

 of it for supplying stores of fresh materials for class use, 

 and enough for connecting the work of the student upon 

 living things with the world of which they are a part. 



If time can be taken for but one of the introductory 

 studies on the relations between flowers and insects, Study 

 5 is the one that should he chosen. Full blooming clumps 

 of flowers (preferably of some specialized bumble-bee 

 flower, such as the snap-dragon, the great blue lobelia, 

 butter and eggs, or turtle-heads) will be needed. If not 

 accessible in nature, they may be easily provided Avith a 

 little forethought at planting time: all give handsome 

 landscape effects in border plantings. 



For the series of ecological studies on diving beetles 

 (studies 55 to 58 inclusive), some means of determining the 

 beetles being needed, a key to the North American genera in 

 the family Dytiscidas is presented on the following pages. 

 The number of our species in each genus is indicated by 

 the arabic numeral standing before the name of the genus 

 (in parenthesis) : and limited distribution is indicated by 

 abbreviations for the name of the region in which it is known 

 to occur. 



