96 
Psyche 
[June 
engendered on the paper. The mixture used as an indicator was an 
aqueous solution of ferric chloride and potassium ferricyanide. In 
the presence of secretion this mixture turns to an intense blue (the 
secretion acts as a reducing agent, causing formation of Prussian blue) 2 . 
Several beetles were subjected to traumatic stimulation, either by 
pinching single legs or antennae with forceps, or by touching various 
regions of the body with a hot probe. Any one such stimulus invariably 
induced a prompt aimed discharge (Plate IO, figs. 1-4). As expected, 
the discharge was always from one gland alone, providing the stimu- 
lus had been a unilateral one. Thus, stimulation of a leg or antenna 
of one side, was followed by an ejection from the gland of that side 
only. Similarly, when one side of the head or abdomen was touched 
with a hot needle, only the gland from the corresponding side dis- 
charged. But when the head was touched on both sides simultaneously, 
or when the abdomen was seized with broad-tipped forceps, then the 
discharge was a synchronous one from both glands. 
Chlaenius cannot revolve its abdominal tip upward and around so 
as to spray upon its back. Touching the thoracic dorsum or elytra with 
a hot needle caused the animal to discharge forward under the abdo- 
men in the usual fashion. Under such circumstances the traumatized 
region is likely to receive at best an incidental spattering of droplets. 
A fair idea of the usual range of the spray can be obtained from 
figures 1-4 in Plate 10. Range is determined by the downward angle 
at which ejection occurs, hence the most anteriorly directed discharges 
are the farthest reaching. Maximum spray impact was within a 
radius of 10 cm., although occasional droplets nearly always surpassed 
this range, and sometimes reached as far as 50 cm. away. 
The number of discharges that could be elicited from each gland 
of beetles that had remained undisturbed for two previous weeks 
ranged from two to four (five beetles tested). As a rule, the bulk 
of the secretion is expended with the first discharge; a much more 
scanty spray pattern is produced by the second discharge, and the 
third and fourth leave no more than a few scattered spots at close 
range. 
Only three specimens were available for dissection, but this suf- 
ficed to establish the overall similarity of the glands to those of 
Chlaenius velutinus Duftschmid, briefly described and diagrammed 
by Dierckx (1899). The two glands are situated symmetrically on 
both sides of the midline in the posterior dorsal abdomen (Plate 11, 
2 We are indebted to George M. Happ for suggesting the use of this par- 
ticular indicator mixture. 
