72 
Psyche 
[December 
spouses to anal glands were negligible. Furthermore, artificial trails 
made with 2-heptenone, the anal gland secretion of pruinosus (M. S. 
Blum, in litt. ) , caused negligible responses. 
In a third series of experiments, the hind-gut, poison apparatus, 
Dufour’s gland, and ventral organ were assayed in a laboratory 
colony of the primitive dolichoderine Monads bispinosa (Olivier).* 
The unusually restless and aggressive nature of the Monads workers 
required the following modification in procedure. Straight trails 
75 cm. in length were drawn down the middle of a clean glass plate. 
Three workers were then released, one at a time, and allowed to 
wander over the glass plate, crossing and re-crossing the trail. A 
positive response was recorded when the worker persistently followed 
the trail to its end. Of 18 workers thus exposed to trails made suc- 
cessively from 6 ventral organs, 17 gave positive responses. The re- 
sponses of workers in triplicated control experiments using the other 
abdominal organs were all negative. 
After the chief source of the odor trails in the three dolichoderine 
species had been located, bioassays were made across species, in order 
to determine the extent of species-specificity of the trail substances. 
As shown in table 2, each species appears to have a different substance. 
Table 2. Intra- and interspecific trail-substance tests employed in the 
present study. Only intraspecific tests produced positive responses ( + ). The 
results of all interspecific tests employed were negative ( ). Interspecific 
tests not attempted are 
Source 
Monads 
indicated by a question mark. 
Recipient 
Liometopum lridomyrmex lridomyrmex T apinoma 
bispinosa 
occidental humilis 
pruinosus 
sessile 
M. bispinosa + 
? — 
? 

L. occidentale ? 
+ 
? 
— 
/. humilis 
- + 
— 
— 
1. pruinosus ? 
? — 
_L 
1 
— 
T. sessile 
j> 
? 
+ 
Further, the Dufour’s glands and ventral organs of Monads bispinosa 
were assayed with laboratory colonies of the myrmicine ants Cremato- 
gaster lineolata (Sav), So/enopsis geminata (Fabr.), and S. saevissi- 
nia (Fr. Smith). The ventral organ induced no detectable response 
in these species. The Dufour’s gland caused no response in the 
Crematogaster but, quite unexpectedly, caused strong trail-following 
in Solenopsis saevissima! In fact, single Monads glands consistently 
drew out approximately the same number of S. saevissima workers as 
single saevissima glands. It was also determined that a single Monads 
Collected at Palmar, southern Costa Rica. 
