Chemical Releasers of Social Behavior. X. An Attine Trail Substance in the Venom of a Non-Trail Laying Myrmicine, Daceton armigerum (Latreille).
Psyche 73:150-155, 1966.
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CHEMICAL RELEASERS OF SOCIAL BEHAVIOR.
X. AN ATTINE TRAIL SUBSTANCE IN THE VENOM OF A NON-TRAIL LAYING MYRMICINE)
DACETON ARMIGERUM (LATRE1LLE)l.
BY M. S. B L U ~
C. A. PORTOCARRERO~~
Although the poison gland secretion may provide species in several myrmicine genera with a readily available source of odor trail phero- mone, this venom doe9 not represent a highly species-specific secretion. It has been demonstrated recently that odor trails prepared from extracts of the poison gland are non-specific even among unrelated genera) although specificity may be absolute when these extracts are tested on species in the same genus (Blum and Ross, 1965). 'The lack of specificity of the poison gland extracts appears to be due to the fact that trace constituents. which are common to different venoms. are employed by different genera as odor trail releasers. Thus, al- though members of .two genera may be employing different trail sub- stances, they will follow trails prepared from each other's poison glands because their odor trail compounds are present in both venoms. Since some of the trace conlpounds in the venoms synthesized by un- related trail-laying myrmicines appear to be similar) it would not be surprizing if the venom of a non-trail laying species contained a trace constituent which was the same as the odor trail pheromone employed by trail-laying members of this subfamily. The purpose of this present paper is to report on the occurrence of just such a case. Daceton armigemm (Latreille) a primitive member of the tribe Dacetini, contains in its venom a powerful releaser of trail following for membeis of three attine genera as well as for an inqui- line cockroach which is associated with one of these genera. The biology of Dizceton has been studied in detail by Wihon ( 1962). Daceton workers hunt singly and no evidence of trail laying or recruitment was observed either in the field or in the laboratorv. The large eyes of Daceton workers appear to endow them with 'This work was supported in part from two grants from the University Council on Research of Louisiana State University 'Department of Entomology, Louisiana State University, Baton Rouge, Louisiana.
'Present address: Department of Communications, Michigan State Uni- versity, East Lansing, Michigan.
Manuscript received by the editor June 29, 1966.
19661 Bluuz and Portocarrero - Chemical Releasers 151 Table I. Response ~f attine species and a species of Attaphila to artificial trails prepared from extracts of the poison gland of Daceton armiuerum.
I Test species
1 Daceton armigerum
' Acromyrmex coronatus
1 Acromyrmex nr. coronatus
' Atta texana
1 Atta9hiZa sp.
No. of workers
No. of workers
exceptional vision and they are able to pursue their prey for con- siderable distances (Wilson, I 962).
The two colonies of Daceton that Wilson studied were strictly aboreal and in no instance did he see workers move from the trees to the ground. However, in the single Daceton colony which we observed we noted three workem on the leaf litter adjacent to the base of their nest tree, making no apparent effort to forage on the leaves, and two other workers some distance from their colonial tree. Under the nest tree there were two small shrubs separated from the overhanging tree by at least three feet. A Daceton worker was rest- ing on each shrub. These workers only could have reached these shrubs by walking across the leaf litter under their nest tree or by falling from the tree onto the shrubs. These observations suggest that under certain conditions Daceton workers may not be totally arboreal.
METHODS AND MATERIALS
A nest of Daceton was located in a large tree in a nursery at Buenos -4ires, 25 kilometers south of Pucallpa, Peru, near the Rio Ucayalli. The colony consisted of three fragments in two branches of the tree. Approximately 600 workers were collected from the nest and were transported to Pucallpa for odor trail studies. Their poison glands were extracted in absolute ethanol. These ethanolic extracts were employed for preparing circular trails (Moser and Blum, 1963) and Daceton and Atta cephaloies (L.)4 workers were tested on these trails. The living Daceton workers were transferred 4Collected at Pucallpa, Peru.
to Tingo Mai-ia, where further artificial trail testing was performed using chloroform solutions of the Daceton poison glands. The fol- lowing species were :dso tested on the trails: Acromyrmex coronatus Acromyrmex nr. coronatus (F.) 5, and a cockroach, Attaphila SP.~, which was found in the fungus garden of A. coronatus. The Daceton worlcers then were frozen and packed in dry ice for aii- ti-ansport to the United States. Workers of Trachymyrmex se@tentrionaZis ( M(:Cwk) 6, Sericomyrnzex urichi Fore17, and Atta texana buckle^)^ were tested on artificial trails pi-epared from methylene chloride solutions of poison glands dissected from the frozen Daceton workers.
Although Daceton workers do not follow artificial trails prepared from their own polson gland secretion, these trails release strong trail following in attine members of the genera Trachymyrmex, Acromyrmex, and Aita (Table I). On the other hand, workers of Serico??~jv-mex urichi did not follow trails prepared from the venom of Daceton. The concentration of the attine odor trail pheromone in thr venom of Dacct~n appears to be the same as it is in the venoms of the attines. Extracts which were prepared from Daceton and Atta poison glands of equivalent size exhibited about the same odor trail potencies after serial dilution.
It is quite likely that the Attaphila are responding to the same compound in the vencin of Daceton as are the attines. &loser (1965) has shown that AtiaphiZa fungicola Wheeler will follow artificial trails prepared from the venom of both A. texana and T. septentrio- nalis. Although hqcser reported that A. texana workers were more sensitive to the odor trail pheromone than the cockroaches, we noted that the Attaphila held to the artificial trails much more tenaciously than the ant workers in any of the genera. Since Sericonzyrmcx urichi did not follow artificial trails prepared from the venom
of Daceton, we wished to determine whether or not this attine would respond to artificial trails prepai-ed fi-om the poison glands of other attines and vice versa. Assuming that the venom of Daceton contains a compound which is si~nilar to those en~ployed by several of the attine genera as trail substances, then 5Collected at Tingo Maria) Peru.
6Collected at Baton Rouge, Louisiana.
7Collected at Trinidad by Prof. Neal A. Weber) Department of Biolcgy, Swarthmore College, Swarthmore) Pa.
sCollected at Pineville, Louisiana.
19661 Blunz and Portocarrero - Chemical Releasers I53 Table 2.
Numbers of SericomyrmexJ Tra~hy~myrmex, and Atta workers responding to the poison gland secretion in the artificial test. Number of replication,^ in parenthesesg. Test s~ecies
Trachymyrmex A tta
0 (8) 44 10)
the failure of Sericomyrmex to follow Daceton trails would indicate that its trail pheromone was different from those of the other attines. Circular trails were prepared from extracts of the poison glands of 8. urichi,
T. septentrionalis and A. texanaJ and the response of workers of each species to the trails was determined. The results, presented in Table 2, demonstrate that S. urichi does not follow the odor trails of A. texana or T. septentrionalis. Similarly, the trail sub,stance in the poison gland secretion of Sericomyrmex releases virtually no trail following in workers of T. septentrionalis and is only slightly active when tested with workers of A. texana (Table 2). DISCUSSION
Although Daceton armigerum does not lay odor trails, its venom contains a substance which is either similar or identical to the trail pheromones employed by attines in the genera Trachymyrmex, Acromyrmex, and Atta. In all probability this substance is a trace constituent of the poison gland secretion produced by Daceton. The venom of Daceton is rich in proteins which solidify when the poison vesicle is ruptured in the air. An attine odor trail pheromone can be readily extracted from the solidified venom without a measur- able weight loss occ~irring and it is probable that a trace component is being removed dLiring the extraction process. Similarly) the odor trail pheromones can be extracted from the solidified attine venoms without causing any detectable weight loss in the venomous residues. The attine venoms) like that of Daceton, are rich in proteins but in addition, the poison gland secretions of the attines contain large series of free amino acids which cannot be detected in the venom of Daceton.
More evidence that the venom of Daceton contains an attine odoi- trail ph~romme is derived from the fact that the Attaphila follow - -
'Ten workers per replicate.
I54 Psyche [June
the artificial Daceton trails.
Moser ( I 965 ) has demonstrated that
another cockroach species, Attaphila ftdngicola, follows artificial at- tine trails, and Echolls (1965) has seen this cockroach on trails of A. texana in the early morning (I a#m.)
Obviously these blattids
can maintain a close mociation with their Atta hosts because of their ability to follow the odor trails of the ants. Thus, since members of the genus Attaphila appear to be following the same trail substance as the attines employ, these cockroaches would be expected to follow artificial Daceton trails if their venom contained an attine trail pheromone. It should be added that the Attaphila also follow artificial trails of both Acromyrmex species, as they woulld be expected to do.
The evidence concerning Sericomyrmex is also circumstantial but is equally pel-suasive. Previously it had been shown that there was no specificity in the trail substances produced by four attine genera which encompassed the broad phylogenetic spectrum of the tribe Attini (Blum et al., 1964). Since these attines follow each other's odor trails, then they would be expected to follow the artificial Daceton trails if these trails contained a substance which was chemi- cally similar to their ctpparently common odor trail pheromones. On the other hand, if an attine produced a trail substance which was different from the one being employed by these several attine genera, then this attine wou!d respond neither to the artificial trails of these other attine genera nos to the Daceton trail. Sericomyrmex urichi is the first member of an attine genus which has been shown not to respond to the artificial trails prepared from the poison gland secre- tions of other attine genera. Weber ( 1966) considers Sericomyrmex a somewhat aberrant member of the higest genera and it is certainly distinguished from at least two of the other higher attine genera by this apparent emploj~ment of a different trace constituent as an odor trail pheromone.
The other gland zssociated with the sting, Dufour's gland, also has been shown to be an unexpected source of a myrmicine trail phero- mone. Wilson and Pavan (1959) reported that the Dufour's gland secretion of the dolichoderine Monacis bispinosa (Olivier) contained a powerful trail substance for the fire ant Solenopsis saevissima (Fr. Smith) which produces its trail substance in Dufour's gland. How- ever, M. bispinosa synthesizes its own trail pheromone in Pavan's gland, a special orgm which lies on the sixth abdominal sternite. Thus the function of the Dufour's gland secretion in M. bispinosa is completely unknown but it is obviously not employed for laying odor trails. It seems eveident that M. bispinosaJ like DacetonJ pro-
19661 BZum and Pwtocar~ero - Che17z icaZ Releasers 1 55 duces some natural products in its sting-associated glands which are also produced by nxmbers of the Myrmicinae. It is not unlikely
that the natural products' chemistry of the glands associated with the ant sting will continue to be characterized by the presence of common products, some of which are employed as trail substances. Under these circumstances we may anticipate that the Formicidae will continue to be a rich source of unsuspected trail substances whose specificities wi11 be at best, unpredictable. SUMMARY
Artificial trails prepared from the poison gland of Daceton armi- gerum (Latreille) , a rnyrmicine which does not lay odor trails, cause trail following in attine species in the genera Trachymymex, Acro- nzyrmex, and Atta.
An inquiline cockroach, Attafihila sp., also fol- lows trails prepared from the venom of Daceton. The poison gland secretion of Daceton apparently contains a trace constituent which is similar or identical to the odor trail pheromone used by these attine genera. An attine species in the genus Serico.myrmex responds neither to artificial Dmeton trails nor the odor trail pheromones of Atta or Trachymyrmex.
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1966. Private communication.
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