The mandibular gland secretion of the ant, Myrmica scabrinodis

ABSTRACT. The volatile secretion of the mandibular gland of the common elbowed red ant, Myrmica scabrinodis Nyl., is shown to consist of ethanal, ethanol, acetone, 3-hexanone, 3-hexanol, 3-heptanone, 3-heptanol, 3-octanone, 3-octanol, 6-methyl-3-octanone, 6-methyl-3-octanol, 3-nonanone, 3-nonanol, 3-decanone and 3-undecanone. The electroantennographic response to the major components was recorded and compared with some related compounds. Behavioural tests were carried out on the major constituents, showing that 3-octanol is an attractant for workers, that 3-octanone increases the effect of 3-octanol, and 3-nonanone augments the linear speed of the ants.     

Comparative study of the mandibular gland secretion of four species of Myrmica ants

The mandibular glands of the two species of ant, Myrmica ruginodis and Myrmica sabuleti contain a similar mixture of compounds, but the proportions are different. M. sabuleti produces ethanol, propanone, methylpropanal, 3-hexanone, 3-hexanol, 3-heptanone, 3-heptanol, 3-octanone, 3-octanol, 6-methyl-3-octanone, 6-methyl-3-octanol and 3-decanone. With the exception of 3-decanone these compounds were also found in M. ruginodis. These compounds were also found in M. rubra and M. scabrinodis.In both species now studied, the mandibular gland contents attract the workers and cause a large increase in their linear speed. In M. sabuleti these behavioural activities are due to 3-octanone and 3-octanol: the attraction of these two compounds in a synthetic mixture is exactly like that of an isolated mandibular gland; the compounds act in synergy to cause an increase in the ants' linear speed. Workers of M. ruginodis specifically respond to a mixture of ethanol, 3-octanone and 3-octanol: the alcohol only moderates the ethological action of the ketone, which is a true attractant and causes a very large increase in the ants' velocity; ethanol also attracts workers, acting in this respect in synergy with 3-octanone.These chemical and behavioural results are combined with those previously reported (Cammaerts-Tricot, 1973; Morganet al., 1978) to explain the responses of M. rubra, M. ruginodis, M. sabuleti and M. scabrinodis workers to isolated mandibular glands from each of these four species.     

Phéromones agrégeant les ouvrières de Myrmica rubra

The workers of Myrmica rubra aggregate around a source of one of their secretions, which can be called ‘alarm pheromone’, and also around workers of Lasius flavus. The mechanism of these aggregations differ.Both L. flavus workers and a solution in liquid paraffin of 3-octanol, one of the mandibular gland compounds, act as an arrestant for the workers of M. rubra. Both Dufour's gland secretion and a source of 3-octanone, the major compound of the mandibular gland secretion, are true attractants.The poison gland secretion, a mixture of 3-octanone and 3-octanol in liquid paraffin and a solution in liquid paraffin of 3-nonanone, a minor mandibular gland compound, all induce klinokinesis. The secretion of the mandibular glands and the secretion of the venom apparatus both cause positive klinokinesis and taxis. These locomotory reactions increase the probability that an object, marked by nest mates with these secretions, will be detected by several workers.When presented alone, 3-octanone is the only attractive compound in the mandibular gland secretion. However, a mixture of 3-octanone and 3-octanol (15 per cent of 3-octanol in the vapour phase) is detected more easily by the ants. The diffusion coefficients of the two compounds are different, and a mixture of these substances creates not only a quantitative but also a qualitative odour gradient. This may explain the synergy of the mixture.     

The volatile components of the mandibular gland secretion of workers of the ants Myrmica lobicornis and Myrmica sulcinodis

The mandibular glands of workers of M. lobicornis produce a mixture of 3-alkanones and 3-alkanols in the C₆–C₁₀ carbon chain length range, in addition to nanogram amounts of acetone, ethanal and 2-methylpropanal. Ethological studies have shown that the three major constituents, 3-octanol, 3-octanone and 3-decanol, are also the major pheromonally active components. When presented together they stimulate an alarm response in the workers similar to that induced by a worker's crushed head.In M. sulcinodis the mandibular gland secretion is composed of a mixture of the same ketones and alcohols, but in different proportions.     

Behavioural activity of pure chiral 3-octanol for the ants Myrmica scabrinodis Nyl. and Myrmica rubra L.

ABSTRACT. The mandibular glands of Myrmica ants contain, among other substances, 3-octanol, a chiral substance, 90% of it being the R -enantiomer in M. scabrinodis Nyl., ruhra L. and ruginodis Nyl. (Cammaerts et al. , 1985). Pure R and S 3-octanol has been prepared and tested on M. rubra and scabrinodis , workers. Both species react specifically only to the R enantiomer; in M. rubra this constituent arrests foragers briefly, and in M. scahrinodis it attracts them and incites them to walk more quickly. It is shown that, in M. scahrinodis , the naturally produced mixture of R and S 3-octanol (proportions of 9:1, v/v) is more active than the pure R enantiomer or a mixture of R and S 3-octanol (5:5 v/v).     

The pheromonal activity of chiral 3-octanol for Myrmica ants

ABSTRACT. The (R)-(-)-3-octanol from the mandibular glands of Myrmica ants is the only enantiomer active as an attractant pheromone for M.scabrinodis Nyl. The S enantiomer is inactive and its presence decreases slightly the response of M.scabrinodis to the R enantiomer. (R) and (S)-2-octanol are inactive.     

Alarm pheromones in the genus Manica derived from the mandibular gland

The alarm pheromones present in the mandibular glands of Manica mutica and M. bradleyi are dominated by a novel C₁₀ ketone, 4,6-dimethyl-4-octene-3-one (manicone). Two other new insect pheromones, 4-methyl-3-hexanone and 3-decanone, are also present. In addition, two characteristic myrmicine alarm pheromones, 3-octanone and 4-methyl-3-heptanone, have been identified as mandibular gland constituents. While manicone functions as a powerful releaser of alarm behaviour for Manica workers a much weaker response was obtained to the other identified 3-alkanones. The significance of the occurrence of 3-ketones in members of the genus Manica and species in other genera of the Myrmicinae is analysed in terms of the accepted phylogeny of this subfamily.     

Larvae of Maculinea rebeli, a large-blue butterfly and their Myrmica host ants: patterns of caterpillar growth and survival

Maculinea rebeli caterpillars spend their final instar as specific parasites of colonies of the ant Myrmica schencki . This paper describes 14 experiments in which 604 caterpillars were reared with six species of Myrmica . About 40% of caterpillars died during an initial period of integration: survival was significantly greater among the larger caterpillars, in M. schencki nests, and in nests that had ant-brood present. The growth of the survivors was extremely variable. After three weeks they had gained 2–18 times their initial body weight and appeared to belong to two distinct types: fast and slow developers. Only 11% of caterpillars died during the next 37 days of growth, before a fall in temperature to below c. 14 C caused them to overwinter. By then, the caterpillars weighed from 5–90 mg (mean 22 mg).
Caterpillars of all weights lost 33% of their mass during winter, and 8% died, before rising temperatures caused growth to resume in spring. Ofthe 363 that survived winter, 44% died during a period of spring growth and 12% pupated after about seven weeks. The latter came mainly from the largest caterpillars before winter and pupal size (mean weight 81 mg) was also related to prewinter caterpillar size. The remaining 44% of post-winter caterpillars continued to grow slowly and then entered another quiescent phase and were still alive after one year in the nest. A small number of these pupated in the second year, an average of 404 days after adoption.
It is calculated that an average-sized Myrmica schencki colony of 350 workers can produce 4–5 adult butterflies; this laboratory result agrees well with field observations. The results are discussed in the light of a previous behavioural study.     

Caste and colony variations in the chemical composition of the cephalic secretions of the African weaver ant, Oecophylla longinoda

ABSTRACT. Considerable differences were found in the composition of the volatile cephalic chemical of the castes of Oecophylla longinoda. The mandibular glands of minor workers contain a series of primary alcohols, predominantly 1-hexanol, 1-octanol and 1-nonanol, together with nerol and geraniol. Hexanal, 2-butyl-2-octenal and 3-undecanone (components of the mandibular gland secretion of major workers, and which are important stimuli in alarm communication) are absent. Major workers are attracted and arrested by high concentrations of nerol, which is part of a possible mechanism for communication within the nest. The heads of males contain a pungent secretion, which may be used in defence; the major constituents are five aliphatic acids. The quantities of both main and trace constituents of the mandibular gland secretion of major workers were found to vary between colonies collected in different areas of West Africa.     

Dufour's gland secretion of Myrmica rubra: Chemical,electrophysiological, and ethological studies

The major volatile compounds of the Dufour's gland secretion of the ant Myrmica rubra have been identified as acetaldehyde, ethanol, acetone, and butanone, in the approximate ratios of 35:3:40:25, with a total content of 12 ng per gland. Ethological tests have shown that three effects recognized earlier for the Dufour's gland can be attributed to these components. Acetaldehyde synergized by ethanol produces an attractive effect on foraging workers. Acetone induces an increased linear speed, and changes in sinuosity of movement are induced by ethanol synergized by butanone. Ethanol, butanone, or mixtures of all four induce the deposition of Dufour's secretion on the foraging area.     

Alarm pheromones of the Attini: Their phylogenetic significance

The volatile components present in the mandibular glands of a number of species of the attine genera Cyphomyrmex (1 species), Trachymyrmex (3 species), and Acromyrmex (2 species) were investigated and compared with those present in Atta. The extracts were found to consist of mixtures of a number of compounds. All but one of these mixtures contained some or all of the following compounds: 3-octanone, 4-methyl-3-heptanone, 3-octanol, and 4-methyl-3-heptanol. The behavioural responses of Trachymyrmex and Cyphomyrmex workers to these compounds were tested. A common chemical heritage based on 3-ketones and 3-alcohols appeared to exist among the genera studied. The chemical data were compared with an accepted phylogeny of these genera to see whether it supported the phylogeny.     

A comparison of mandibular gland volatiles from ants of the bull horn acacia,Acacia collinsii

GC–MS analyses of dichloromethane extracts of the mandibular glands from three obligate symbiotic Psuedomyrmex ant species of Acacia collinsii from Costa Rica: Pseudomyrmex flavicornis (synonym Pseudomyrmex belti), Psuedomyrmex spinicola, and Psuedomyrmex nigrocincta, showed distinct differences in the 16 ketones, 15 alcohols, 2 aldehydes and 2 carboxylic acids that were identified. Different compounds were the major component from each species: P. flavicornis, 3-octanone; P. spinicola, 4-methyl-3-heptanone; and P. nigrocincta, 3-methyl-2-hexanol. The secretion of P. flavicornis contained 10 compounds not found in the other species, including the two terpene alcohols, citronellol and geraniol. The secretions of P. spinicola and P. nigrocincta had 12 compounds in common, that were not found in P. flavicornis' secretion. The similarity of the mandibular gland secretion of P. spinicola and P. nigrocincta may indicate that they are more closely related to each other than either is to P. flavicornis. The components from the mandibular gland of Crematogaster rochai, another ant associated with this acacia, are 2- and 3-methylbutanoic acid, 3-octanone, 3-octanol, 6-methyl-3-octanol and 3-nonanone.     

Larvae of Maculinea rebeli, a large-blue butterfly, and their Myrmica host ants: wild adoption and behaviour in ant-nests

The behavioural interactions between caterpillars of Maculinea rebeli Hir. and their Myrmica ant hosts were studied, both in the wild at the time of adoption, and inside captive nests of six Myrmica species.
In the wild, freshly moulted, final instar caterpillars left their food-plants at a time of day that coincided with the peak foraging activity of Myrmica (18:00-20:00 h). Once on the ground, caterpillars made no attempt to search for Myrmica but settled and waited for foraging ants to find them, which took up to 1.5 h. There was no adoption ritual: foragers of any Myrmica species picked up the caterpillars within 1–4 sec of discovery, and carried them directly to their nests.
Caterpillars grew from < 2 mg to 110 mg in laboratory ant-nests. About 60 mg was gained in autumn but 40% of this was lost during the winter, while the temperature was < 14 °C. Although caterpillars survived best with their normal host, Myrmica schencki , they could also survive in the nests of other Myrmica species. The presence of queen ants had no effect upon survival. The behaviour of the caterpillars was described and illustrated: this included the production of secretions that were drunk by the ants, begging for food and direct feeding by ants. The preferred solid food was ant eggs.
The results are discussed in terms of the social biology of Myrmica ants. It is hypothesized that Maculinea rebeli caterpillars mimic the touch pheromones of ant worker-larvae. This would explain the inability of ants to recognize caterpillars before touching them, their immediate adoption by any Myrmica species after discovery, host specificity inside wild ant-nests, the absence of queen-effect and the intimate attention of host workers.     

Some characteristics of the visual perception of the ant Myrmica sabuleti

Abstract. Using classical conditioning techniques, this study aims to determine what the ant Myrmica sabuleti can see and discriminate. It appears that workers see distinctly vertical as well as horizontal segments 1, 2, 3, 5, 10 and 15 mm wide and 1, 2, 3, 5, 10 and 15 cm long. They can also see distinctly horizontal segments (0.5 × 3 cm) located at 1, 2, 3, 5 and 10 cm height, but do not see such a segment situated at 15 cm height. This allowed the assessment of their maximum distance of vision. Myrmica sabuleti workers also see distinctly vertical segments (0.5 × 3 cm) sloping backwards towards the horizontal at different angles (90, 60, 45, 30, 15 and 0 °). Consequently, M. sabuleti workers see cues lying horizontally on the ground and have a stereovision of a portion of their environment. The species also see distinctly black circles of different sizes located horizontally above them. Thus, they are able to see distinctly slightly modified patterns located aside, below, above as well as before them, and have a small area of binocular vision that both eyes can look at. Myrmica sabuleti workers' maximum distance of vision is directly proportional to the square root of the surface of the object observed. Consequently, the smallest vision angular subtense of an object needed to elicit a reaction in M. sabuleti workers is evaluated as being approximately 5 angular degrees.     

The control of Myrmica rubra workers by queens of their own and other Myrmica species and the interaction between queenless groups of workers

ABSTRACT. Queens of two species of the ant genus Myrmica bonded to workers of the species M. rubra L. as the latter emerge from the pupal skin can use these workers nearly 6 months later to arrest gyne formation in sex-competent larvae of the same species. Queens of M. ruginodis Nylander var. microgyria (Brian & Brian, 1949) are as good at this as the natural M. rubra , but those of M. sabuleti Meinert (of a race close to M. scabrinodis) are not. Though the M. sabuleti queens induce normal aggression against sexualizing larvae, they are unable to prevent some or all of the workers feeding larvae as though they were queenless. However, queens from different colonies of M. rubra adopted by queenless populations of workers in spring, control their brood-rearing behaviour perfectly. M. rubra workers from different colonies bring gynes to maturity from female sexual larvae at different average sizes. When workers from two such sources are mixed in equal proportions, the size of gyne larva produced after a week's culture corresponds with that of one of the worker populations; it is not intermediate in size. Also, large workers can rear larger gyne-larvae than small workers of the same age. This is only true if the workers have been living with queens all the time from emergence as an imago to the moment the experiment was set. Size mixtures only achieve the same size larvae as a pure culture of small workers would. A possible reason for this is that small workers exclude the larger ones from the nursery areas of the nest.     

Operant conditioning in the ant Myrmica sabuleti

Operant conditioning could be obtained in the ant Myrmica sabuleti by presenting to the workers, during a six-day period, an apparatus containing either sugared water or meat as a reward. The conditioning obtained using sugared water as a reward was short lasting. A reconditioning was more persistent and lasted four hours. The ants' response was very precise, since they exhibited it only in front of an apparatus identical to that used during the training phase. Operant conditioning obtained using meat as a reward was more pronounced than that obtained by using sugared water, probably because meat is more valuable as a reward than sugar for the species studied, which is essentially a carnivorous one. Such a conditioning was rather persistent. Indeed, a first operant conditioning obtained by using meat as a reward could still be detected after seven hours, and a reconditioning was still significant after eight hours. One day after this eight-hour period without rewarding the ants, the response was higher again and a further day later, it was still significant. Since the operant conditioning is easy to perform and quantify and since the ants' response is very precise, such a conditioning can be used for further studying M. sabuleti workers' visual perception.     

No sympatric speciation here: multiple data sources show that the ant Myrmica microrubra is not a separate species but an alternate reproductive morph of Myrmica rubra

No aspect of speciation is as controversial as the view that new species can evolve sympatrically, among populations in close physical contact. Social parasitism has been suggested to yield necessary disruptive selection for sympatric speciation. Recently, mitochondrial DNA phylogeography has shown that the ant Myrmica microrubra is closely related to its host, Myrmica rubra, leading to the suggestion that sympatric speciation has occurred. We investigated the relationships between the two ant forms using mitochondrial and nuclear DNA sequences, microsatellite genotyping and morphometrics. Molecular phylogenetic and population structure analyses showed that M. microrubra does not evolve separately to its host but rather shares a gene pool with it. Probability analysis showed that mitochondrial DNA data previously adduced in favour of sympatric speciation do not in fact do so. Morphometrically, M. microrubra is most readily interpreted as a miniature queen form of M. rubra, not a separate species. Myrmica microrubra is not an example of speciation. The large (typical M. rubra) and small (M. microrubra) queen forms are alternative reproductive strategies of the same species. Myrmica microrubraSeifert 1993 is consequently synonymized here with M. rubra Linnaeus, 1758.     

Tetracosane on the cuticle of the parasitic butterfly Phengaris (Maculinea) nausithous triggers the first contact in the adoption process by Myrmica rubra foragers

Phengaris (Maculinea) butterflies are social parasites of Myrmica ant colonies. Larvae of the parasite are adopted by the ant workers into the colonies. Apparently, chemical signals are used by Phengaris nausithous Bergsträsser larvae to mimic those of the host brood to be recognized by the ants. In the present study, chemical extracts of ant brood and butterfly larvae using four different solvents are tested in behavioural choice assays in search of compounds involved in the adoption process. Tetracosane is the main shared compound in all brood extracts of Myrmica rubra L. and in all larvae of P. nausithous. The attractiveness of tetracosane for M. rubra workers is confirmed by testing synthetic tetracosane in behavioural choice assays, suggesting that the adoption ritual may be initiated by tetracosane.     

Isolation, identification, synthesis and biological activity of volatile compounds from the heads of Atta ants

S-(+)-4-methyl-3-heptanone has been identified as the principal alarm pheromone of Atta texana and Atta cephalotes. Both enantiomers of 4-methyl-3-heptanone have been synthesized and their biological activities have been compared on both species of ants. Comparison of the geometric averages of response ratios, at threshold concentration levels on A. texana, showed S-(+)-4-methyl-3-heptanone to be about 100 times more active than the (?) enantiomer. A similar analysis also showed no inhibition of the activity of S-(+)-4-methyl-3-heptanone by the (?) enantiomer. A less rigorous study on A. cephalotes showed S-(+)-4-methyl-3-heptanone to be about 210 times more active than R-(?)-4-methyl-3-heptanone.Both ant species produce 3-octanone, possible trace amounts of 3-octanol, and both diastereomers of 4-methyl-3-heptanol. A. texana also produces (+)-2-heptanol, 2-heptanone, and 3-heptanol. A. cephalotes contains trace amounts of 2-heptanone.     

Field trapping of Metamasius hemipterus with synthetic aggregation pheromone

The five synthetic pheromone components of the West Indian sugarcane borer (WISB), Metamasius hemipterus (L.) (Coleoptera, Curculionidae) were tested in the field. The combination of sugarcane (SC) and the major pheromone compound, 4-methyl-5-nonanol (1) was attractive. However, the addition of 2-methyl-4-heptanol (2) or 2-methyl-4-octanol (3) was required to reach high catch levels while 5-nonanol (4) or 3-hydroxy-4-methyl-5-nonanone (5) did not enhance WISB attraction. The redundancy phenomenon, here reported for the first time in rhynchophorinous species, was observed between compounds 2 and 3. SC +1 +3 was more attractive than living male baits, however, the sex-ratio of the catches was equivalent between both treatments. The sex-ratio of catches was affected by the qualitative composition of the pheromone formulation. Compound 3 had a sexual role, attracting more females while 5 seemed to play an aggregation role, luring both sexes in the same proportion.