191 ")] 
Miittkowski and Whedon: Gomphus Cornutcs 
97 
of the abdomen ( australis is not known to the writers) ; villosipes 
and furcifer usually have the dorsum of eight black, ten entirely 
yellow; cornutus and whedoni have a basal spot on eighteen with 
a yellow dorsal spot. 
ECOLOGY 
The material defining the life history of Gomphus cornutus 
Tough was collected at Mankato, Minn., on June 7th and 10th, 
1913. It consists of ten exuviae, and a male and a female freshly 
emerged. The photographs (figs. 3 and 5) illustrate the condi- 
tion of the imagoes when discovered. The pond from which 
they were taken, commonly called Front Street Pond, is a shallow 
body of water but a few rods in extent, retained on three sides by 
embankments for the accommodation of streets or railroads: 
a perpetuated fragment of one of the boggy branches of the 
Minnesota valley on the outskirts of the town. Half its area is 
occupied by Sagittaria, Typha and other rooted plants, while 
its open water is usually well-filled with green algae. On one side 
the shore and bottom are quite rocky, on the other, where most 
of the vegetation is found, deep mud. It was in the open water 
just off the rocky shore that the masses of algae floated, upon 
which this dragon fly transformed (fig. 7). Here the water was 
from two to three feet deep. All the exuviae were found in the 
same position, supported by thick mats of algae and half sub- 
merged in water. 
As to other conditions, the weather from June 1st to 10th 
was very bright and yet moderately cool. This may bear some 
relation to the hour of the day when the unhardened individuals 
were discovered clinging to their cast skins: about 2 p.m. in 
each case, the female on June 7th and the male on the 10th. 
Both were very soft and entirely helpless. The male, which had 
crawled upon a floating, water-logged cat-tail stem, was scarcely 
able to retain his hold. A fairly heavy wind swept the pond 
every day and may have been one of the factors governing the 
transformation of the nymph at the surface. However, some 
search failed to reveal a single case of transformation upon an 
erect stem. 
Although Anax, Leucorrhinia and other dragon flies were 
very plentiful about the pond on these dates, there was no sign 
