Boletín de Entomología Venezolana

Bol. Entomol. Venez. N. S. 5(20) :165-182 Diciembre, 1990

ON THE COMMUNICATION SYSTEMS OF THE DOLICHODERINAE ANTS

Aztecaforeli and Conomyrma sp.

Klaus Jaffe, María I. Alvarez and Ornar Colmenares*

RESUMEN •Ambas espcies tienen habitos de forrajeo diurnos. Conomyrma sp es monogínica y construyenidos en la arena hasta unos 50 cm de profundidad consistentes de numerosas camaraspequeñas. A. forelí es poligínica y anida en ramas huecas en árboles. Experimentos delaboratorio revelaron lo siguiente:

a.- Ambas especies utilizan reclutamiento químico masivo con una feromona de caminoproducida por una glándula abdominal que informa sobre la presencia y localidad delalimento. La concentración de la feromona regula la intensidad del redutallÚento.Laduración de la actividad de la feromona es de mas de una hora para A.foreli y menos de 30mino para Conomyrma sp.

b.- Los territorios son reconocidos en forma colonia-específica, gracias principalmente aseñales quíllÚcas. A. forelí marca su territorio con secreciones del tórax, llÚentras queConomyrma sp lo hace con secreciones del abdomen. La duración de la actividad de la marcaes de cerca de una hora paraA.foreliy de unos 30 minopara COllomyrma sp.

C.- Compañeras de nido son reconocidas gracias a un olor colonia especifíco, absorbido sobrela cutícula. El olor es producido en la región cefálica, probablemente por la glándulamandibular.

d.- Ambas especies producen feromonas de alarma cefálicas y abdominales.

Los resultados se comparan con los sistemas de comunicación de otras hOrllÚgasy se discutenalgunos aspectos ecoetológicos.

ABSlRACT

Both species have diurnal foraging habits. Conomyrma sp is monogynic and build nests withmany small chambers up to 50 cm deep in the sand. A.foreli is poligynic and uses ho1cs intrees as' nes!. Experiments in the laboratory revealed the following:

a.- Both species use chellÚcal mass recruitment with a traíl pheromone from an abdominalgland which gives information about the presence and localization of food. Its concentrationregulates the amount of recruitmen!. The fade out time of a traíl is over one hour for A. foreliand less than 30 min for Conomyrma sp.

* Departamento de Biología de Organismos. Universidad Simón Bolivar, Apartado 80659,Caracas 1080.Venezuela.

166 Bol. Entomol. Venez. N.S. 5(20): 1990

b.- The ants have a territorial behaviour in which territories are recognized colony-specifi­cally, mainly by chemical cues. AJoreli marks its territories with a pheromone from a thoracicgland, whereas COllomyrma sp does it with a pheromone from a gland in the gaster. Thefade-out time of the pheromone of A. foreli is about 1 h whereas for COllomyrmasp it isabout 30 mino

e.- Nestmates are recognized by colony specific odour, which can be adsorbed on the cuticle01'lhe insects. The odour is produced in the head, probably by the mandibular gland.

d.- Both ants produce cephalic and abdominal alarm pheromones .

.Rcsults are compared to the communicalion systems of other Formicidae and someeeoethologieal apecls are diseussed.

INTRODUCTION

Azteca spp. are one of the most common ants in the neotlOpics. They are reported to fonnclose associaton with plants, protecting them fromherbivores whereas the plant plOvide themwith shelters and/or food (WHEELER 1942). Besides casual observalions, little is knownabout their behaviour. Even less is known about the behaviour of COllomyrma spp., in spiteofthe fact that they seem to be common in the neotropics.

Few works on rccruitment and alarm-defense systems, mainly on Tapilloma spp. and¡ridomyrmex spp. (CAVILL & PHYLLIS 1965, TRAVE & PAVAN 1956, SZLEP &JACOBI 1967, COURET & PASSERA 1979, ROBERTSON et al., 1980) tell us about thebehaviour of the ants of the sub1'amily Dolichoderinae, in spite of the fact that they are oncthe most important members of neotlOpical ecosystems, competing in importance, regardingbiomass, with the Myrmicinae.

In this work we make a preliminary survey 01'the more conspicuous communication systemsand characlcrize in more detail the recnlitment syslem and the agonistic commucationsystems of two Dolichodcrinae ants. Thc results are compared to the behaviour known 1'orants from other subfamilies.

MATER1ALS AND METHODS

Nests of COllomyrma sr. (types of wich were deposited at Museo de Entomología, Institutode Zoología Agrícola, U.C.V., Maracay, Venezuela) were excavated flOm the beach ofHiguerote, whcreas nests A. foreli were collected from dry cocoa pods in Caucagua, EstadoMiranda, Colonies were established in the laboratory al 25 6 ºC and 40-70% RH, usingnatural illumination. The size of the colonies varíed between 500 and 10 000 individuals.

Twenty-two colonies of each species were kept in plastic containers (50 x 50 cm). Ants wereoffered a plaster of París nest, cast a 12 cm diameter Petri dish. This nest had excavatedchambers which were covered with a glass plate and a dark piece of paper. Ants occupiedthese nests with their brood and queen. They were offered water, honey and dead crickets.Details of experimental procedures will be given together with the results.

RESULTS

Ja[fe y otros, Communication in Dolichoderinae 167

General Observatíons:

Conornyrma sp. is monomorphic and builds its nests in the sand, nexUo the roots of treesand bushes. The main activity observed in the field was foraging on extrafioral nectariesof mangrove trees. The nests had 3 to 5 entrances, separated 50 to 60 cm from each other,interconnected through a complex system of galleries (2-4 mm internal diameter) which leadto several oval chambers (up to 20) 10 to 50 cm. deep. Sexual brood were always found inseparate chambers. Colonies in the field produced alates during February and March. A.foreli, which is also monomorphic, uses natural cavities of trees lo establish parts of theircolony. Trails run through the tree and between trees, from one cavity to anolher, were thebrood is kept. Dry cocoa pods are nearly always occupied by this an!. The dry seeds of thefruits are perforated with 2 to 3 small holes and used by the ants lo keep pupae. We foundup to 7 physogastric queens in one podo Sexual s and sexual brood occupied separate pods.In the lab. queens were found always in the same chamber. Field colonies produced alatesall year around, with an increased alate production between April and June.

The daily foraging rhythm, measured as the number of ants on a 90 cm2 área on Ihe foragingtable ofthe laboratory colonies, wa~ counted once each 60 min. Colonies were kcpt with foodat libitum beginning 24 h prior to the counting. Results showed that A. fin'eli had its foragingactivity mainly during the day with a peak of activity two hours before sunse!. At night,activity levels dropped to about 15% of that of peak hours. COllornyrrna sp. had a moreuniform foraging activity pattern. The activity peaked at sunset and never dropped below30% of the peak value during the 24 h. cycle.

Recruitment to food:

In both species, workers frnding the food retumed to the nest dipping the gaster on the ground.A few seconds afterward, nestmates emerged from the nest and walked to the food followingthe route the frrst scout made for homing. No leader ant was seen guiding the ants to the food.Removal of the frrst ants in the column did not interrupt recruitme!. Thus, chemical massrecruitmet was suspected to be used for recruitmet to food by both species (JAFFE et al..1985).

Bioassay 1: Food was offered to the colony on a specific place on the foraging table. Thenumber of ants going to the food and the number returning to the nest was counted during Imin intervals for 60 mino Time zero was the moment when food was made available to the

colony. The data obtained served to graphically (Fig. 1) determine the rapid increase phase(see also JAFFE & HOWSE, 1979), and to calculate the parameters on Table l.

Results: Data on Table I suggest that both species use chemical mass recruitmet (WILSON1962, JAFFE 1980). 80th regulate the amount of nestmates recruited in accordance to foodquality andjor the length of the previous starvation period. That is, more workers are recruitedto the food (greater Max. Nr. of ants recruited) or they are recruited faster (steeper slope ofthe recruitment curve) when the starvation period was longer or if the food quality was better.

168 Bol. Entomo!. Venez. N.S. 5(20): 1990

Conomyrma sp. differs fromA.forel; in that the recruitment curve ofthe former showed twodistinct phases (Fig.l). For Conomyrma sp. the slope of the frrst phase, but not that of thesecond phase (Fig. 1, Table 1), differed statistieally when the food-nest distance was variedClose observation showed that during the first phase, the recruited ants eanle mainIy from theforaging arca, whereas during the second phase, the main body of workers carne from thenest. In the case of A. foreli ants from the nest participated in reruitment from the beginning.

Exocrine glans produeing the traíl pheromone:

In order to fmd the source of the trail pheromone, the following bioassay was developed:

Bioassay J/: Whatmann 42,4.25 cm filter papers, were placed at the nest entrance for 48 h.A. thinned Pastellr pipet was used to make a 3.5 cm diameter circle on the paper with one antequivalent (the extract of the glands of one ant in 0.5 mi methanol) of the different extraets.The number of ants lcaving the nest, and the number of them following the artificial traíl waseounted during l min intervals, as well as the number of consecutive 1/4 segrnents of theeircurnferenee fol1owed by those ants following the artificial trail.

Reslllts: Data on Table II showed that in both species, the trail pheromone comes from thegaster. It is probably produced by the Pavan's gland as in other doliehoderine (PAVAN &RONCHETTI 1955, WILSON & PAVAN 1959, WILSON 1965, JAFFE 1984). Gasterextracts of each speeies have an attractive effeet on nestmates and orientate them at the sametime. No interspecifie trail following between both species was observed.

Additional tests showed that higher eoneentrations of gaster extract recruited a greaternumber of workers. No saturation effeet or replllsive effect of concentrated gas ter extractseould be detected for the concentration range tested (0.5 to 5 ant equivalents/paper). Thus,the trail pheromone gives information about the presence of food, its spatial posilioB and itsquality, i.e. pheromone concentration regulates amount of recruilment.

The duralion of lhe orienlation effect of the trail pheromone, if applied as extraet, is aboutone hour in A.forel; and less lhan 30 min ConomymUl sp. (Table 111).

Territorial hchaviour:

When a worker 01' any of the lwo speeies was placed on Ihe foraging area of a differentconspeeific colony, an inerease in the speed of movements ofthis inlruder eould be observed.As the foreign ant was often but nol always attacked, Bioassay ID was developed in order totest the responses of anls to new and to alien conspecific territories and to study the reaction01' workers lo differcnt types of territories.

Bioassay llI: Two Whatmann 42, 4.25 cmdiameter filter papers (A and B in Table IV), weréplaced for 48 h on the foraging table, next to the nest entranee of the colonies. For the test,both filler papers ("sirnulated territories") were removed, and 10 mino later (unless statedotherwise in Table IV) were replaced by two other papers. These papers could be new (N),the same as the ones just removed (C), or they could come from a different conspecific colony(D), wich had explored them for at least 48 h. Five min after placing the papers in the arenat he number of ants on the two papers was counted during l mino

laffe y olros, Commwúcation in Dolichoderinae 169

When lesting extracts for territorial activily, the papers were impregnated with methanolexlracls (E) of one ant equivalent of lhe respective body part, or wilh pure solvenl (S), andleft at room temperature for 5 mino (or more, see Table Il) in order to allow lhe solvent loevaporate. The papers were then lested as describe above.

Results: The resulls (Table IV) show that workers of both species dislinguish between aterritory previously explored by themselves, and a new territory or one previously explorcdby another conspecific colony. Conomyrma sp. was also able to distinguish between a newpaper and one prcviously explored by another conspecific colony.

Experiments using extracts (Table V) suggest that the recognilion signal is produced by theants and thus, that they mark their lerritory with a pheromone. The possible source of Iheterrilori~l pheromone seems to be different for the two species. A. foreli seeIlL~to producethe pheromone from a thoracic gland, whereas COllomyrma sp. seems lo produce it from anabdominal gland. The effect of a lerritory marked with exlracts of these body parts, wasequivalent to that of territories previously explored by them, as measurcd by Bioassay ur.No dissection of glands was possible due to the small size of the workers.

Experimenls with COllomyrma sp. showed that filter papers, placed in the foraging arena neaea pennanent food source, weretreated differently by the ants than papers placed in the arena,in places fae from the nest entrance and from the food (p < 0.01, Mann-Whitney's U- test).The latter were treated like new filler papers (p = 0.443, Wilcoxon's matched paies test). Nodifferences in the response to simulated territories placed on different parts of the foragingarena could be observed with A. foreli.

When two Collomyrma sp workers from different colonies were placed in a Petri dish outsidetheiTcolonies on a filler paper from Bioassay lIT, they showed aggression. The ant iniliatigthe fight was in 11 out of 12 ca"es the ant on its own territory, i.e. on the paper previouslyexplored by its colony (p < 0.008, Sign test). When testing papers with extracts in the sameway, the number of tests in which fights were initiated by an ant on its own territory; by anant on a foreign territory; and in which there was no fight, were as fo))ow: Head exlract,3:5:4; thorax, 2:3:7; gaster 6: 1:5. The only statistically meaningful ratio is the one for thegaster extract (p = 0.06, Sign test). Sirnilaely, for A. foreli for 15 replica/es, the number offights iniated by Ihe ant on its own territory was 7, and 2 for the foreign ant; whereas on anew paper, the same workers initiated only 2 fights each. This difference is highly significant(p < 0.001, Fisher's exact probability test).

Nestmate recognition:

Bioassay IV: Two workers drawn at random, one from the nest where the test was performed(C, forcontrol), and the other froma different conspecific colony (E, forexperimental), werepicked up with deodocized plastic forceps and placed anywhere on the foraging arca of thecontrol colony. The behaviour of the resident workers toward the intruders was observed andrecorded on a tape recorder for later quantification.

Results: When workers were placed on the foraging area of a foreign colony, they werefrequently attacked Not all the intruders were attacked to the same extent, but E ants were

170 Bol. Entornol. Venez. N.S. 5(20): 1990

always grasped by workers and carried to the borders of the foraging arena (Table VI, liveants).

No colony specific brood recognition (Nymphal stage) was detected for either ofthe species,as the time of removal, time of the duration of antennalion by workers, numbers of workersattracted and number of workers alanned was the sarne for nestmates and intruders (p > 0.1in all cases, Wilcoxon's rnatched pairs test).

Foreign Conomyrma sp. queens and males were attacked more vigorously than workers. Theywcre also hindercd from reentering their own nest, although not attacked by their nestmatesonce thcy Icft Ihe nest. A. foreli a polygynic species, attacked foreign queens only if Ihecolony had an active queen. Queenless colonies accepted in 4 out of 5 cases a foreign queen.That is. Ihe queen was seen alive for al least 6 weeks after introduction to the colony.

Reeognition Signals:

Bioassay V: Dead workers or parts ofthem were placed near the nest entrance on the foragingarca of the colonies. Always two workers or parts were presented simultaneously lo thecolonies. One of them originaled from a neslmate (C) whereas the other carne from a differenlconspecific colon y (E). The time resident workers took before removing each of Ihepresented objecls was measured for A. foreli. For Conomyrma sp, the occurrence or not ofremoval, during a 10 minoobservation period was noled.

Dead workers were freeze dried by applying pressures ofO.OO1mm Hg al -20ºC lo lhem usinga vacuum pump. Freeze dried workers were irnpregnated with odors from differenl bodyparts in the following way: Frceze dried anls were placed logether wilh two freshly crushedbody parts of workers from a specific colony in a 2 mI glass vial. Care was taken in orderlo avoid direct contact belween the freeze dried ant and the crushed body parto The vial wassealed and left al room temperature for 30 mino After tbis period, the freeze dried ant wastaken out and used for tests.

Results: The time a dead ant remained on the foraging area before it was picked up, wasdifferenl fm forcign conspecific anls compared lo nestmales, when bolh were presentedsimultaneously ([ahle VI). Only in the case of freeze dried ants, was the probability ofremoval 01' a residenl anl Ihe sarne as for a foreign ant. These experiments indicated thatfreeze drying removed lhe nestmale recognilion signal. This signal was present only in thehead of Ihe workcrs. Olher body parts were nol recognized colony-specifically. When afrceze dried A. foreli anl was impregnaled with vapors from head, thorax or gaster, andassayed, the recognition signal reappeared on the freeze-dried ant, only in the case ofvaporsfrom the head, reproducing the colony-specific behaviour.

These experiments indieate the presence a colony-specific odour, which has to be a complexof volatile substances in order to evaporate and impregnate a freeze dried anl colony-speci­fically. The source of Ihe odour is in both cases a cephalic gland.

laffe y otros, Conununication in Dolichoderinae 171

Alann pheromones:

Bioassay VI: One body part (head, thorax or gas ter) was crushed over the center of a 9 cmdiameter Whatmann 42 filter paper. The paper had concentric circles, one cm apart, drawnwith a pen, in order to facilitate observation. The paper was placed in the foraging arena ofa colony and the behaviour of the workers was observed during 10 mino and recorded on atape recorder for posterior quantification. Eight replicate observations for each experimentalsituation were perfomed.

Results: For CmlOmyrma sp., alann behaviour, characterized by fasl Illovernenls of Iheworkers and lifting ofthe head and anlennae, was induced by crushed hcads and abdomens.Crushed thoraces produced no visible reaction by the workers. The crushed heads producedalann for 3 mino (range 2-3 min.) and to distances up to 6 cm. from Ihe source. After Ihistime an increascd exploration ofthe paper was observed for up to 9 mino Crushed abdornensinduced alann for only 0.5 min (range 0.4-0.55 min) at distances of up to 2 cm, but attractedants, i.e. orientated to the center of the paper, for up to 15 mino

A. foreli also showed alann behaviour toward crushed head~ and abdomens, but nollowardthoraces. Alann behaviour in this species was characterized by fast movements ofthe workersand lifting of the gaster. Heads induced alann at distances from the source of up to 1 cm. for10 mino (range 8-10 min.), Gasters alanned workers at distances up to 2 cm. for 15 mino(range 10-16 min.). Heads induced orientation toward the center ofthe paper but gasters didnoto

DISCUSSION:

The comunicati~n system used for recruitment to food of the two Dolichoderinae speciesstudied is very similar. Both have colony- specific recognition systems, prohably based oninter-colony differences of the different components of the cephalic alann pheromones, asis the case in the advanced Myrmicinae (1AFFE 1983) and Formicinae (JAFFE & SANCrIEZ1984).

Territorial Behaviour:

Both have territorial marking behaviour fulfliling the criteria for a territorial pheromone(lAFFE & PUCHE 1984), which are:

1.- Workers secrete a pheromone on the territory.

2.- Workers recognize the territorial mark colony- specificaUy.

3.- Workers on territories with the pheromonal mark from its colony have some kind ofadvantage, compared to foreign conspecific workers on the same territory.

4.- A marked atea should be respected by conspecifics. The end result should be a reductionin aggressive interactions between colonies, because colonies are spaced out more than wouldbe expected from a random occupation of suitable habitats.

172 BoL Entomol. Venez. N.S. 5(20): 1990

Criteria 4 is a sufficient but not necessary condition for territory. I.e., criteria 3 could befulfilled without fulfillment of criteria 4.

The presence of terntorial marking behaviour seems to be a characteristic shared only byadvanced Formicidae (HOLLDOBLER & WILSON 1977, JAFFE & PUCHE 1984, JAFFE& SANCHEZ, 1984, JAFFE, 1987).

The two species of ants use different glands to produce their territorialpheromone. Thissupports previous suggestions (JAFFE & PUCHE 1984, JAFFE & SANCHEZ 1984, JAFFE1987) that teritorial marking behavioUT is a relatively recent feature in ant phylogeny.Different ant species have different territorial pheromone sources, even if they belong to thesame subfarnily, eontrary to what OCCUTSwith trail pheromones, in wich the same gland isused by a broad spectrum of related species (JAFFE 1984). However, we can not exclude

other glands as SOUTcesofterritorial pheromones, as our bioassays were performed in the lab.and ás different markers eould be used by the species to mark different types of teritories.

Ncstmate Recognition:

The nestamate reeognition system seems to be independent ofthe number of queens in the

eolony. The polygynie speeies A. foreli has the same recongnition mechanism as monogyniespecies such as CmlOmyrma sp. or Atta spp. (JAFFE 1983). This eontradicts the suggestionofCROZIER & DIX (1979) and HOLLDOBLER & MICHENER (1980), who proposed thatpolygynic speeies should use a kind of gestalt OdOUTin order to reeognize their nestmates.This is certainly not the case fm A. foreli where on1y the cephalic alarm pheromone is used

as a recognition signaL Chernieal composition of pheromones are very probably genetically[¡xed, and leaming ofthe odour ofthe colony (i.e. the OdOUTof the nestmates) is required inorder to recognize ncstmates.

Alarm Conununication:

A. foreli seems to havc a more complex alarm communieation system compared to eonomyr·nw sp. as hoth. cephalic and abdominal secretions, eomplemcnt each other. The ceph¡¡liepheromone orientates the ants but has a short-Iasting effect, whereas the abdominal alarmpheromone is long lasting hut does not orientate the workers toward the SOUTCCof emission.

In COllomyrma sp. the role ofthe abdominal alarm pheromone is not elear. Its short-lastingeffeet makes it doubtful to be a true alarm pheromone. The attractive effeet produced by thecrushed gasters may be due to the trail pheromone. In any case, a more detailed study ofthe alarm behavioUT of these species is needed.

Reeruitmcnt to food.

Also the recruitment system of these Dolichoderinae seeIlls to be fairly advanced. That is,the chernical rnass recruitment system (WILSON 1962, JAFFE, 1980) found is similar tothat whieh had been described for the Dolichoderinae Iridomyrmex humilis (See Robertsonet al., 1980), whieh has been classilied as ofthe more advaneedamong the Formieidae (JAFFE

Jaffe y otros, Conummication in Dolichoderinae 113

1984). As in the maJonty of ants, the Dolichoderinae studied seem to use the democraticdecision making system during chemical mass recruitment (JAFFE et al, 1985).

Ethoecological Considerations:

The two species differ in the fade-out timc ofthe different pheromones. Aforeli has longerlasting trail, alarm aud territorial pheromones, compared to C01l0mymUl sp. llÚs is likelyto be related to the different habitats they exploit. A. foreli lives exclusivcly 011 trees. whereasCollomyrma sp. is a terrestrial aut, although foraging also on trees. A.foreli exploits mainlyspalially and temporally predictable resources (Aphid colonies ami extratloral neclarics),whereas Conomynna sp. seems to be a more generalized forager. collecting dead arthropods,and extraOoral neetar of mangrove trees and food residues leti behind by beach tourisls. A.foreli seems to have a more developed lerritorial behaviour comparcd lo C01l"myrnza sp.Evidence forthis is the faet that C01wmyrma sp. does not advertise all theirforaging arena inthe laboratory with territorial pheromone, as A. foreli does. It is known lhat A. foreli is adominant ant in cocoa planlation eeosystems, excluding nearly all other anl speeics fram thetrees they inhabit (JAFFE et al, 1986). Thus, territorial bchaviour seems to be related to lhetype of resourees exploited by thc spceies, Le. each spccies seems to optimizc cnergyexpenditure in marking their territory.

174 Bol. Entorno!. Venez. N.S. 5(20): 1990

p (anova)

24

9

42

meat

24

honey(10%)

10

42

24 .

12

23

honey

12

42

72

honey

11

42

24

No. of replicates:

Fooo-nest distance:

(cm).

t (h) without foodbefore the test.

TABLE 1: Effect of food quality, duration of previous starvation and food-nest distanceon recruitrnent. (Mean and standard deviation of the different parameters usedto characterize the recruitrnent curves. (Bioassay 1).

A: Azteca Foreli.

Food offered: hooey

Max. No. of antsrecruiled in 1 mino

intervals. 34 ± 14. 42 ± 18. 4l± 15. 16± 15b 3 ± le < 0.01

1.3±0.9. 2.4±1.7b 2.3±\.2h 0.7±0.2e 0.1±0.2d

t lomaximunreccruilmenl

(min)

Slope oftherapid increasephase.

26± 6. 26± 8. 22± 6. 24± 8. < 0.05

< (W1

B: ConornyrnIa sp, Food offered: meat.No. of replicates(n): 9 9

Fooo-nest distance: (cm). 32 32

t (h) without foodbefo~ the test. 24 168

9

64

24

p(anova)

Max. No. of ¡mIs recruiledin 1 min inlervak

22 ± 4.27 ± 4b18 ± 4e

t tomaximulI recmitmcnl (min).

40± 440± 544± 5

Slope of lhe phase 1 ofthe recruitment curve.

1.7 ± 0.9. 1.6 ± 0.3. 0.7± 0.3b

Slope of the phase 11ofthe recruitment curve(Fig. 1).

1.5 ± 0.61.6± 0.61.1 ± 0.4< 0.01

> 0.1

< 0.01

> 0.05

Means in each row which differ statistically bctween thern, as determined by Student's t-test(p < 0.05 ), are indicated with different letters (a, b. c, & d). Ifthey have the same letter, theyare not statiscal1y different (p > 0.1). ANOV A indicates the probability of al1 groups beingequal given by a one way analysis of variance.

]affe y otros, ConunwlÍcation in Dolíchoderinae 175

TABLE Il: Number of ants attracted to an artificial trail and number of them followingit (Bioassay 1I).

A: Azteca ¡orel; (n = 7):

Extraet: Methanol Head Thorax Gaster Gaster

('otunnyrma s.p.

Ants/min attracted

(Mean of first 10 min).

19 a29 a18 a31 b

Ants/min followingtraíl (Mean after 30 min).

17a8 a18 a29 [,

1/4 sections foIlowed

12163

(Median, range).

(O-4)a(O-2)a(0-4)a(3-I1)b(0- 5)ab

B: COllomyrma sp. (o = 6):

Extraet:

MethanolHeadThoraxGasterGasler

A·fárdiAnts/min attracted

(Mean of first 10 min).

21 a31 a12 a102 b

Ants/mio. foUowing

traíl (Mean after 10 nlin).

16 a16 a7 a40 [,

1/4 sectioos foUowed

662103

(Median, range).

(0-4)a(0-12)a(0-4)b(3-II)c(2- 5)a

a,b & c indicate statistical1y different medians for each row given byMann- Whitney' s U-test(P < 0.05 ). Medians which do not differ statistcally (p > 0.1) are indicated with the sameletter.

176 Bol. Entornol. Venez. N.S. 5(20): 1990

TABLE ID: Duration of the effect of the trail pherornone extracted from the gaster;Number of 1/4 sections of trail followed. (Bioassay ll).

Time after A. ¡oreli (n = 10)Conomyrma sp (n=6)applieation

MethanolGasterpMethanolGasterp(h)

(Control)extraet (Control)extraet

0.1

6.010.0<0.05

(3-10)(8-16)

0.5

1.2512.0<0.0053.05.0> 0.1

(0.5-3.5)(10-15) (0- 5)(1- 6)

LO

3.07.8<0.002(1.0-5.0)

(4 -11)

2.0

3.03.8>0.05 -

(0.5-8.0)(2.0-11)

pis the probability ofrejeeting HO calculated by Wi1coxon's matched pairs test. n indicatesthe nurnbcr of replicates for each experimcnt.

laffe y otros, Conuuunication in Dolichoderinac 177

TABLE IV: Number of ants attracted lo filter papers previously explored by differenlcolonies. (Bioassay IlI).

A: Azteca foreli (n=20):

Pairs oí papers(A vs B)

Median and range on:A B

pWikoxon's test

CvsNCvsDDvsNC after lit vs NC after 21t vs N

25 (3-102)

30 (6-81)22 (7-261)10(1-30)31(1-59)

61 (9-278)34(7-165)31 (2-294)15 (162)21 (O-57)

<0.0 I

«>-05>0.10d1.05

>0.10

B: Conomyrma sp. (n=IO):

Pairs oí papers(A vs R)

Median and range un:A R

pWikoxon's test

CvsNCvsDDvsNC after 30 mino vs NC after lh vs N

2 (0-4)2 (0-5)2 (0-4)1 (0-4)

2 (0-3)

5 (1-8)3 (1-7)5 (0-8)2 (1-4)

2 (0-4)

dW02«/.001d/.OO 1

dU)02>0.10

The papers had been explored previously by memt>ers ofthe same colollY in which lhe assaywas performed (C), by ants oí a conspecific colony (D), or they were new papcrs (N).

178 Bol. Entornol. Venez. N.S. 5(20): 1990

TABLE V: Median (and range) of the nurnber of ants altraeted to two ftlter papers, plaeedsimultaneously in the foraging arena of a eolony (Bioassay ID).

A: Azteca foreli (n=20):

Extraet

E(C)S(tested after lh.)

Newpaper

17(1-91)20 (1- 70)Head

27 (0-190)21 (4-178)Thorax

21 (0- 66)28(1-67)Abdomen

43 (8-200)59 (8-136)

(tested artcr 5 min)

E(C)E (O)

Head

56 (11-151)43 (6-240)Legless thorax

48 (0-163)58 (7-303)Legs

12 ( 3-307)13(3-128)Abdomen

36 (3-202)39 (5-188)

B: COllomyrnUJ sp. (n=10):

p (Wilcoxon's test)

>0.10>0_10<0.01>0.10

>0.10<0.02>0.10>0.10

Extraet(temed after 30 mim.)

New paperHead1l1Orax

Abdomen

HeadThoraxAbdomen

E (O) S

4 (0- 8)

5 (0- 9)5 (0- 8)

6 (1- 8)4 (0- 7)

6 (1- 9)3 (1- 4)

4 (O- 6)

E(C)

E(D)

4 (0- 5)

4 (1- 7)4 (0- 6)

4 (0- 6)3 (0- 6)

5 (2- 8) p (Wilcoxon' s test)

>0.10<0.05<0.01<0.02

>0.10>0.10<0.03

The eards were impregnated with either an extraet (E), or with pure solvent (S). E(C) standsfor extraets frorn ants of the C colony, whereas (D) corresponds to extracts frorn ants of a Ocolony.

Jaffe y otros, Communication in Dolichoderinae 179

TABLE VI: Time before an ant or a body part of an ant was picked up from the foragingarea of a conspecific colony (or number of ants picked up) during a 10 minperiodo (Bioassay IV & V).

A: Aztecaforeli (n=15):

Part presentedMedian of t (8)C E

pSign test

Live ant >600

Whole body 300Head 1801llOrax 85Abdomen 30Freeze dried ant 30

Freeze dried and impregnated with:Head 71Thorax 25Abdomen 25

B: COllomyrrna sp.:

300

125180120

120

30

281830

<'0.05

<1UH

<0.05>0.10

>0.10

>0.10

<1>'<)05

>0.10

>0.10

Number of ants (out of n) removed

Part presented.

Live ant

Whole bodyHeadThoraxAbdomenHead - thoraxThorax - abdomenFreeze died ant

e

oO

6O

O

275

E

22

161633

21

85

n

24243424

24

24

3416

p

Fisher' s test

<1UlOI

<1>-001

<1).(l01

>0.10

>0.10

<1).001

>0.10

>0.10

C (Control) indicates that the test ant carne from the same colony of the test, whereas E(Experimental) indicates that the test ant carne from a different conspecific colony.

RAPtO IHCREASE PHASf0100OO•••~

80~ ~lit

10

lE~...

40O •z20

10

PHASE 1~

20

130

pHAS( D 140

AZTECA

CONOM'I'RMA

­00O

txl

~l:'t1

lao

~t-

~z¡nVIÑ-$-8

TIME AFTER '000 WAS Of'FEREO (mil\.)

Figure 1. Recroitment curves obtained with Bioassay I.

Jaffe y olros, Communicalion in Dolichoderinae

ACKNOWLEDGEMENTS:

181

Thanks are given lo Alberto Meza for rus lechnical assislance, lo Dr. C. Bosque for crilicallyR::ading an early draft oflhe manuscript, and lo CONICIT, Venezuela for fmancial supportlhrOUgh lhe granl SI-1336. Aztecaforeli was ienlified by John Laltke and Conomyrma sp.by lhe lale Dr. W.F. BUR::n, who thoughl il wa~ probably an a~ yel undcscribed COllomyrmaspecies, c10se lo Conomyrma biconnis.

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