1937] 
Notes on Ptecticus trivittatus Say 
141 
NOTES ON THE COURTSHIP AND MATING OF THE 
FLY, PTECTICUS TRIVITTATUS SAY 1 
By Phil Rau 
Kirkwood, Missouri 
During several summers before these notes were made in 
1930 and also several summers afterwards, large numbers of 
these attractive greenish-colored flies were seen hovering 
in courtship dances above garbage heaps on the rear of a 
lot. They were first observed on the 20th day of May of that 
year and they continued their activities over this restricted 
area until the middle of July; to be exact, they appeared in 
much reduced numbers on July 19th and had completely dis- 
appeared by July 25th. There are probably two generations 
a year, for they again appeared on August 22nd and were 
seen thereafter until September 11th. 
They spend much of their time flying slowly and noise- 
lessly over this “island’ 1 of color and odor commencing 
sometimes as early as 5 :30 in the morning when only a few 
may be seen ; they increase in numbers with the passing of 
the hours and the rising of the temperature. They dance 
almost incessantly throughout the long day, and even into 
the dusk may the motion of their frail forms be seen. To say 
that they dance incessantly is not wholly true for individuals 
often leave the throng to rest on a tin-can or bottle or canta- 
loupe skin. The temperature readings when these dances 
occur varies from 65 to 75 degrees F.; one can, however, 
hardly refer to the phenomenon as a “sun dance” because 
the flies are equally active in sunshine or shade, as well as in 
shadowy stretches splashed with spots of sunlight. Both 
males and females are present in the dance, and the sexes 
are about equal. 
It is, indeed, a pretty sight to see a flock of these flies 
moving in a horizontal plane in more-or-less irregular circles 
"Specimens were kindly identified by Mr. C. T. Greens of U. S. Dept, 
of Agriculture. 
