12 
Psyche 
[June 
In essence, the technique consists of applying the test substances 
topically to decapitated cockroaches, and timing the onset of the 
grooming reflexes that follow. The delay to onset of grooming is a 
criterion of the irritant effectiveness of the sample : the quicker the 
onset, the greater the irritability. 
The droplets of sample were applied with a constant-volume micro- 
pipette (0.4 jul) to any one of three loci: the fifth abdominal sternite 
(on one side of the midline), a tarsus of a metathoracic leg, and a 
cercus. For each locus the grooming reflex induced is unmistakably 
distinct (Eisner, 1961). Each roach was tested three times, once at 
each locus, but the sequence of loci tested was not fixed, nor was the 
same sample necessarily used at each locus. Recovery of 15 to 20 
TABLE I 
O /77-cresol y p - cresol 
# Ch/aenius secretion Y Abacion secretion 
sternal 
O • 
reflex 
V f 
( n.r. = no response) 
tarsal reflex 
O • V ▼ 
cereal 
O • 
reflex 
V f 
4' 22“ 
2' 43" 
2' 17" 
3‘l8" 
r 1 " 1 " 1 " 
1 " 1 " 
1" 2 « 
n. r. 
n.r. 
n. r. 
3'40" 
1 " 2 " 2 " 
1 " 
r 
n r 
n. r. 
n. r. 
n. r. 
1 " 2 " 
2 " 
3 " 
n. r. 
n.r. 
n. r. 
n. r. 
2* 4" 
2 " 
4- 
n. r. 
n.r 
n. r. 
n. r. 
6" 5' 
4“ 
4' 
Table I. Sensitivity of Per'iplaneta americana to the secretions of Chlaenius 
and Abacion, and to the corresponding phenols. Sensitivity is expressed as 
the delay to onset of a grooming reflex (sternal, tarsal, and cereal) following 
topical application of a given sample. The times of delay for the three reflexes 
and four samples tested are given in the vertical columns. For full explana- 
tion see text, part IV. 
minutes was allowed between consecutive tests on the same roach. 
Failure to induce a reflex within five minutes of application was con- 
sidered a negative response (n. r.). Adult female roaches were used 
exclusively. The secretions were obtained by the same techniques as 
used for the chemical analyses (see part II, above). 
The results are plotted in Table I. Unfortunately, with the actual 
secretions, the amount of material available sufficed for only relatively 
few tests. Still, some safe inferences can be made. First of all, as 
expected, the tarsi and cerci, with their relatively thin cuticle, are 
much more sensitive than the abdominal sternite: the reaction was 
always within seconds of application. By contrast, when application 
