396 Wisconsin Academy of Sciences, Arts, and Letters. 
rower, and its fore-legs show a distinct spatulation for the pur¬ 
pose of burrowing in sand and gravel. It is worthy of inter¬ 
est that there is a change in habitat with the growth of the 
larvae. Young larvae frequent the sandy bottoms at depths 
exceeding one meter, hence are distinctly ammophilous (sand- 
loving) ; I have no records of young larvae from rocky areas 
or from any part of the shore line. Older larvae, however, are 
found chiefly in rocky and stony areas, especially on the shore 
line,—hence are petrophilous. 
The situation amounts practically to this: the adults ap¬ 
pear during the first days of June, young larvae will be found 
several weeks later in the deeper sandy bottoms, while at the 
same time an occasional full grown larva may be found in the 
rocky regions of the shore line; after the middle of August 
older larvae will be very common on gravel and rocky shores, 
and exceedingly rare on sandy bottoms, especially those below 
the rachion. A second flight of adults occurs in early August; 
that is, the specimens which failed to emerge in June emerge 
in August. 
C. Order Odonata. (Table 5, p. 475.) 
From the standpoint of adaptation to amphibious life the 
Odonata as a unit have reached the highest development among 
insects. Amphibious existence is ancestral with them, and 
they have equipped themselves for both terrestrial and aquatic 
life during their larval state. For aquatic respiration they 
have the rectal gills (Anisoptera) or caudal gills (Zygoptera), 
while both suborders possess open thoracic spiracles for aerial 
respiration. The latter are impermeable to both water and 
miscible oils (Portier 1911) so that an exchange from an aqua¬ 
tic to an aerial medium, and vice versa, can be effected immedi¬ 
ately. 
In spite of their perfect adaptation to any type of aquatic 
life the Odonata are very sparsely represented in the lake com¬ 
plex. I believe that this is due to the ovipositional habits of 
the adults. Odonata lay their eggs on a free substratum or 
in plants. It is of course obvious that in the second case the 
eggs must be laid in plants which emerge from the water. 
Hence we find this type of species restricted more or less to 
habitats showing emergent vegetation; this includes most Zy- 
