2 Psyche [March- June 
It is the object of the present paper to describe the egg-laying of 
Odynerus ( Rygchium ) rugosus (Sauss) = foraminatus (Sauss) 
as observed and photographed by the glass-tube method. 
Bamboo tubes which served as sheaths for the glass tubes so as 
to afford the requisite darkness of the interior, were tacked on a 
tree-trunk or the side of the house or other comfortable shady 
place, and developments awaited. Light for instantaneous pho- 
tography was secured by reflecting sunlight on the tube by means 
of a mirror. 
The egg is always laid before the prey is captured and the cell 
stored. Trypoxylon and many others reverse this sequence. The 
signal for the egg-laying ceremony consists in the wasp’s turning 
around and backing into the tube. Egg laying is the only act for 
which this orientation is necessary. 
After entering the tube the more or less excitable female comes 
gradually to rest supinely on her wings, with tip of abdomen di- 
rected upward close to the mud partition. The rapid breathing 
movements (air temperature 90° F !) are soon accompanied by 
another type of movement, a comparatively slow, rhythmic con- 
traction of the abdomen, in which the abdominal segments seem 
alternately to telescope and evert as the tip of the abdomen is 
retracted and extended. In the words of the observant young 
assistants: “She’s pumpin’ an egg.” With each extension of the 
abdomen the tip comes in contact with the ceiling. Presently a 
drop of whitish secretion appears and is touched to the ceiling. 
There it sticks; and as the abdomen is withdrawn a thread is 
drawn out and instantly hardens, remaining flexible and tough, 
for subsequent movements of the abdomen do no injury to it. 
The abdominal movements continue uninterruptedly until 
gradually the egg begins to slide out. The motion picture shows 
the egg free for about one-third of its length when a sudden jump 
in the film occurs to the point where the egg is two-thirds emerged, 
the interval marking the time that the camera was being re- 
wound. 
As soon as the egg is free, it is seen to dangle by its thread like 
a tiny pendulum. 
Function of the Thread 
On the adaptive significance of the suspensory thread of the 
Eumenid egg or its possible phylogenic history, the writer has no 
contribution to make. Several observations, however, may be 
cited confirmatory of Ch. Ferton’s contention (Collected Works, 
