414 



GENERAL BIOLOGY 



Fig. 242. Nymph of a stonefly 

 (Perla). 



and easiest obtained, (see appen- 

 dix). 



2. A typical perlid nymph 

 (Perla, Neoperla or Acroneuria) . 



3. Any of the larger species 

 of mayflies. 



4. Any sialid larva (Sialis, 

 Chauliodes, or Corydalis; larvae 

 of the whirligig beetle would 

 answer the same purpose. 



5. A caddis-worm with abun- 

 dant development of gills. 



6 and 7. Damselfly and drag- 

 onfly, data for the addition of 

 which were obtained from the 

 preceding study. 



Study these 

 seven repre- 

 sentativ e 

 forms indi- 

 vidually, and 



write the characters with which we are 

 here concerned in columns in a table 

 prepared with the following column 

 headings: 



Name. 



Order (of Hexapoda). 



Gill type (blood gill, or tracheal gill). 



Number (of individual plates or fila- 

 ments) . 



On w^hat segments (use the Roman 

 and Arabic numerals as indicated 

 in fig. 10, p. 17, so far as possible). 



Form (filiform or lamellif orm) . 



Fig. 243. The larva 

 of an orl fly {Sialis). 



