Impact of the invasive ant Wasmannia auropunctata (Formicidae: Myrmicinae) on local ant diversity in southern Cameroon

The little fire ant, Wasmannia auropunctata Roger, is one of the world's most destructive invasive ants. It has been present in Cameroon for more than four decades, but its impact on local ant diversity is not known. We studied impact of W. auropunctata in three disturbed habitats located in rural and urban areas. We monitored ant diversity in both invaded and noninvaded zones in each area using a combination of three sampling methods: bait, pitfall traps and visual catch in quadrat. We collected 28 species in urban area and 64 in rural area. In invaded zone, W. auropunctata made up 97.72% and 99.96% of all ant fauna and ant species richness decreased to 7 and 2 in urban and rural area, respectively. In accordance with others findings in introduced environments, the presence of W. auropunctata has severely reduced abundance and richness of local ant species in both urban and rural environments in Cameroon. Measures should therefore be put in place to prevent its introduction in natural environment as forest reserves and natural parks.     

The First Cytogenetic Data on Strumigenys louisianae Roger, 1863 (Formicidae: Myrmicinae: Dacetini): The Lowest Chromosome Number in the Hymenoptera of the Neotropical Region

In the present study, the first cytogenetic data was obtained for the ant species Strumigenys louisianae, from a genus possessing no previous cytogenetic data for the Neotropical region. The chromosome number observed was 2n = 4, all possessing metacentric morphology. Blocks rich in GC base pairs were observed in the interstitial region of the short arm of the largest chromosome pair, which may indicate that this region corresponds to the NORs. The referred species presented the lowest chromosome number observed for the subfamily Myrmicinae and for the Hymenoptera found in the Neotropical region. Observation of a low chromosome number karyotype has been described in Myrmecia croslandi, in which the occurrence of tandem fusions accounts for the most probable rearrangement for its formation. The accumulation of cytogenetic data may carry crucial information to ensure deeper understanding of the systematics of the tribe Dacetini.     

Alkylpyrazines: alarm pheromone components of the little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera, Formicidae)

The previous identification of 2,5-dimethyl-3-(3-methylbutyl)pyrazine as the mandibular alarm pheromone of the little fire ant Wasmannia auropunctata (Roger), has been found to be incorrect. Gas chromatography–mass spectrometry (GC/MS) of ant extracts suggested the correct structure to be the regioisomer 2,5-dimethyl-3-(2-methylbutyl)pyrazine, which was confirmed by comparison with the synthetic pyrazine. GC/MS analysis also revealed the presence of an additional disubstituted alkylpyrazine which was identified as 3-methyl-2-(2-methylbutyl)pyrazine. Headspace sampling of confined ants with SPME and Porapak Q followed by GC/MS analysis showed 2,5-dimethyl-3-(2-methylbutyl)pyrazine as the major volatile released by W. auropunctata workers while 3-methyl-2-(2-methylbutyl)pyrazine was only detected in trace amounts. In laboratory bioassays, W. auropunctata workers were attracted and arrested by both pyrazines, although the results were not always consistent. Synthetic pyrazines generally attracted as many W. auropunctata workers as were attracted to a single crushed ant. However, higher numbers of W. auropunctata were arrested by crushed ant treatments than by synthetic pyrazines in all bioassays but one.     

Experimental Evidence of Large-Scale Unicoloniality in the Tramp Ant Wasmannia auropunctata (Roger)

We examined intraspecific colonial aggressiveness in Wasmannia auropunctata (Roger), a tramp species originating from the neotropics. By observing the results of one-on-one confrontations, we compared the behavioral responses of workers originating from six New Caledonian locations (introduced range) and four Brazilian cocoa plantations (original range). We recorded interindividual aggressive behavior on four levels ranging from physical contact, with no aggressive response, to prolonged aggressiveness, including stinging by one or both ants. In Brazil, we often observed high intraspecific aggressiveness between populations originating from distant locations, indicating that W. auropunctata may behave as a multicolonial species in its native range. In New Caledonia, paired encounters resulted in low agonistic behavior, as shown by the absence of full attacks (which include stinging by one or both opponents). Our results suggest that W. auropunctata behaves as a single supercolony throughout New Caledonia and that the scale of its unicoloniality (widespread colonies with interconnected nests without aggressiveness between workers originating from distant areas) is different in introduced and native populations. According to the present study, it seems likely that differences in intraspecific aggressiveness between native and introduced populations of W. auropunctata contribute to its invasive success.     

Immediate impacts of invasion by Wasmannia auropunctata (Hymenoptera: Formicidae) on native litter ant fauna in a New Caledonian rainforest

Abstract For the last 30 years, Wasmannia auropunctata (the little fire ant) has spread throughout the Pacific and represents a severe threat to fragile island habitats. This invader has often been described as a disturbance specialist. Here we present data on its spread in a dense native rainforest in New Caledonia. We monitored by pitfall trapping the litter ant fauna along an invasive gradient from the edge to the inner forest in July 1999 and March 2000. When W. auropunctata was present, the abundance and richness of native ants drops dramatically. In invaded plots, W. auropunctata represented more than 92% of all trapped ant fauna. Among the 23 native species described, only four cryptic species survived. Wasmannia auropunctata appears to be a highly competitive ant that dominates the litter by eliminating native ants. Mechanisms involved in this invasive success may include predation as well as competitive interactions (exploitation and interference). The invasive success of W. auropunctata is similar to that of other tramp ants and reinforces the idea of common evolutionary traits leading to higher competitiveness in a new environment.     

Field suppression of the invasive ant Wasmannia auropunctata (Hymenoptera: Formicidae) in a tropical fruit orchard in Hawaii

The little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae), is an invasive ant that forms supercolonies when it successfully invades new areas. W. auropunctata was first reported in Hawaii in 1999, and it has since invaded a variety of agricultural sites, including nurseries, orchards, and pastures. Amdro (hydramethylnon; in bait stations), Esteem (pyriproxyfen; broadcast bait), and Conserve (spinosad; ground spray) were tested for their efficacy against W. auropunctata in a rambutan, Nephelium lappaceum L. and mangosteen, Garcinia mangostana L., orchard by making treatments every 2 wk for 16 wk. Relative estimates of ant numbers in plots was determined by transect sampling using peanut butter-baited sticks. Significant treatment effects were observed on weeks 13-17, with reductions in ant counts occurring in the Amdro and Esteem treatments. During this period, the reduction in ant numbers from pretreatment counts averaged 47.1 and 92.5% in the Amdro and Esteem plots, respectively, whereas ant numbers in the untreated control plots increased by 185.9% compared with pretreatment counts. Conserve did not cause a reduction in ant counts as applied in our experiment. No plots for any of the treatments achieved 100% reduction. Pseudococcidae were counted on branch terminals at 4-wk intervals. The two predominant species, Nipaecoccus nipae (Maskell) and Nipaecoccus viridis (Newstead) were significantly lower in the Amdro and Esteem treatments on week 16 compared with controls. Many W. auropunctata were found nesting in protected sites in the orchard trees, which may have compromised the ground-based control methods. Absolute density estimates from shallow core samples taken from the orchard floor indicated the W. auropunctata supercolony exceeded 244 million ants and 22.7 kg wet weight per ha.     

Acute exposure to low-dose radiation disrupts reproduction and shortens survival of Wasmannia auropunctata (Hymenoptera: Formicidae) queens

Irradiation is a postharvest quarantine treatment option to control ants and other hitchhiker pests on fresh horticultural products exported from Hawaii. The radiotolerance of the invasive little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae: Myrmicinae), was studied to determine a dose sufficient for its control. Queens from each of five laboratory microcolonies started from five geographic locations in Argentina were irradiated at 20, 50, 70, or 100 Gy or left untreated as controls and then followed for 13 wk to observe colony growth. In general, queen survivorship, and the number of eggs, larvae, and pupae observed in the microcolonies decreased with increasing irradiation dose. In the 50-, 70-, and 100-Gy treatments, the number of eggs observed was reduced by 68, 66, and 76%, respectively, compared with untreated control microcolonies. The number of larvae in the 50-, 70-, and, 100-Gy treatments was reduced by 99.6%, and only one pupa was observed in the 50-Gy treatment and none in the 70- and 100-Gy treatments during the 13-wk experiment. Queens in the 100-Gy treatment had significantly reduced longevity compared with queens in the other treatments. Radiation doses > or = 70 Gy stopped reproduction in W. auropunctata queens and should be sufficient as a phytosanitary treatment. Information from additional invasive ants in Myrmicinae and other subfamilies is needed before recommending a generic irradiation treatment for ants.     

四川省蚂蚁区系研究（膜翅目：蚁科）

研究了四川（含重庆）蚂蚁的种类和分布,得知目前分布于四川的蚂蚁共有78种,分别隶属于5亚科27属,并发现1新种;古蔺立毛蚁Paratrechina gulinensis,sp.n。提供了新种的特征描述,根据地貌环境和气候的差异。将四川蚂蚁分为4个动物地理域,并讨论了四川蚂蚁区系的特点。     

Lenomyrmex, an enigmatic new ant genus from the Neotropical Region (Hymenoptera: Formicidae: Myrmicinae)

Abstract. We describe a new myrmicine ant genus, Lenomyrmex , with four new species: L. mandibularis (type species) and L. foveolatus from Colombia, L. wardi from Ecuador and Colombia, and L. costatus from Panama. The new taxon is clearly distinguished from other myrmicine ants by the following combination of characters: (1) mandibles elongate-triangular, with crenulate masticatory margin three times longer than basal margin, and bearing a series of ten to twenty minute peg-like denticles that arise along and immediately behind the masticatory margin; (2) frontal lobes poorly expanded laterally, partly covering the antennal fossae; (3) large and deep antennal fossae; (4) antennal scrobes absent; (5) eyes protuberant; (6) petiole pedunculate, with poorly defined node and with an anteroventral subpetiolar process pointed anteriorly. The affinities of this new taxon within Myrmicinae remain unclear and the observed characters do not permit it to be included satisfactorily in any of the known tribes or genus groups of the subfamily.     

Food abundance and foraging patterns of natural colonies ofPolyrhachis vicina Roger (Hymenoptera: Formicidae)

The foraging pattern ofPolyrhachis vicina Roger, the composition of food collected, and the abundance and distribution of food sources were studied. Results showed:

Complex Nesting Behavior by Two Neotropical Species of the Ant Genus Stenamma (Hymenoptera: Formicidae)1

Two Neotropical ant species, Stenamma expolitum Smith and S. alas new species (described here), exhibit three unusual nesting behaviors: (1) they build architecturally sophisticated nest entrances that elevate the nest opening away from the surface; (2) they maintain multiple identical nests but occupy only one of them; and (3) they keep a round “door pebble” at the nest entrance, with which they plug the opening in response to army ants. Adaptive hypotheses for these behaviors are discussed, including the possibility that there are multiple lines of defense against army ant predation.     

小火蚁的形态特征、分布危害及监测与防控

小火蚁Wasmannia auropunctata Roger被世界自然保护联盟（IUCN）列为最具危害性的100种入侵物种之一,已从其原产地南美洲扩散到除南极洲以外的每个大陆,近期被报道成功入侵中国。本文对小火蚁的分类学与形态特征进行了描述;简要探讨了小火蚁的原产地范围和在全球的扩散历史,进一步阐述其对农业生产、人类健康、生态系统等方面的影响;同时,介绍了小火蚁的监测与调查方法;最后就小火蚁的检疫、化学防治与生物防治等防控技术进行了归纳,以期提升大众对小火蚁的认识并为积极应对小火蚁的入侵提供参考。     

Further records of ants (Hymenoptera: Formicidae) from Iran

Wide ranging surveys of the ant fauna of Iran have enabled us to add a further 30 named species to the country list. A review of almost all the published literature and of photographs of unidentified specimens within the public domain gives a grand total of 248 species, from seven subfamilies and 37 genera. In the majority of instances, our own specimens were compared with type images available from antweb.com. This has led us to propose new or revised status for Cataglyphis turcomanica Crawley 1920, Lepisiota integrisquama (Kuznetsov-Ugamsky, 1929), Lepisiota surchanica (Kuznetsov-Ugamsky, 1929) and Messor obscurior Crawley 1920. We note that the total includes a number of what may be misidentifications and a small number of named species that seem unlikely to occur in Iran.     

郑氏红蚁Myrmica zhengi雌性生殖蚁新发现（膜翅目：蚁科）

记述了郑氏红蚁Myrmica zhengi Ma & Xu雌性生殖蚁新发现。该蚁与工蚁相似,但头部具3枚单眼;复眼大,具深色斑块。唇基圆凸成球状,端缘平直。中胸背板发达,遮盖前胸背板,背侧平坦,后胸背板明显;并胸腹节刺粗大,基部宽,约为并胸腹节基面长的一半。上颚具有光泽;并腹胸具纵形刻纹;腹柄,后腹柄背面和腹部光亮。体棕色,中胸背板边缘具直立毛,后腹柄后部具1列横直立毛。其余刻纹被毛的分布情况似工蚁。标本存放于陕西师范大学动物研究所。     

Microsatellites for the Neotropical ant,Camponotus leydigi (Hymenoptera: Formicidae)

Ants (Hymenoptera: Formicidae) are dominant social insects that play important ecological roles in terrestrial ecosystems. Camponotus leydigi (Forel) is widely distributed in the Neotropical region and is frequently found in the Brazilian cerrado savanna interacting with plants and other insects. Field observations indicate that C. leydigi has a polydomous nesting habit, but little is known about the genetic relationship among workers. In this study, we identify the first nine microsatellite loci for C. leydigi that will allow further investigation on its genetic diversity. We used a microsatellite-enriched library method. According to this method, repetitive sequences are captured with (CT)₈ and (GT)₈ biotin-linked probes, with subsequent recovery by streptavidin magnetic-coated beads. We observed that eight loci were polymorphic. The mean (± standard error) observed and expected heterozygosities were 0.55 ± 0.23 and 0.73 ± 0.28, respectively. The rarified allelic richness ranged from 1 to 5.32. The polymorphism contents were similar to diversity estimates found in markers previously developed for other Camponotus ants. These markers will be useful for future studies on population genetics and ecology of Camponotus ants in cerrado, including nesting ecology, colony structure, dispersal and conservation.     

Five polymorphic microsatellite markers for the study of Cardiocondyla elegans (Hymenoptera: Myrmicinae)

We describe primer sequences for five microsatellite markers in Cardiocondyla elegans, an ant species with ergatoid males. Polymorphism of these loci was investigated using 236 individuals from 22 colonies from four locations. The microsatellites are dinucleotide repeats with four to 16 alleles, and the observed heterozygosity ranges from 0.244 to 0.720. We characterized these markers for the study of the population as well as the social structure of colonies.     

Control of mango seed weevils (Sternochetus mangiferae) using the African Weaver Ant (Oecophylla longinoda Latreille) (Hymenoptera: Formicidae)

The mango seed weevil, Sternochetus mangiferae (Fabricius), is among the major threats to mango production in Tanzania. Sternochetus mangiferae is primarily a quarantine pest whose presence inside the fruits restricts access to new foreign markets and leads to rejections of fruits destined for export. Management options for the pest have largely been dependent on field sanitation and application of synthetic insecticides with some success. Thus, more sustainable methods are needed to substitute insecticides, as this may also open up opportunities for organic markets. We conducted field experiments for two fruiting seasons in a mango plantation at Mlandizi, Kibaha district, along the coastal belt of Tanzania to evaluate and compare the effectiveness of the predaceous ant Oecophylla longinoda Latreille with foliar insecticidal sprays of Dudumida (70 WDG Imidacloprid) in controlling S. mangiferae. Mango seed weevil infestation was assessed fortnightly based on infestation marks on developing fruits starting eight weeks after fruit set to early ripening phase. Between 50 and 64 fruits were sampled, well labelled in jute bags, secured and transported to the laboratory at Kibaha Biological Control Unit (KBCU) for incubation at room temperature using rearing transparent containers. Two weeks later, the fruits were dissected and inspected for the presence of S. mangiferae developmental stages. Field and laboratory results indicated that fruits from trees that were occupied by O. longinoda and from those treated with insecticide showed significantly (P < 0.0001) lower incidences and infestation rates by S. mangiferae than from untreated trees. Furthermore, there were no significant differences between the insecticide and the weaver ant treatments. We conclude that in our experiments, O. longinoda is an efficient biological control agent for a long‐term control programme and is comparable to insecticide (Dudumida) in suppressing S. mangiferae and may be used in Tanzanian mango plantations.     

Raiding behavior of the dulotic antChalepoxenus muellerianus (Finzi) in the field (Hymenoptera: Formicidae,Myrmicinae)

Summary Little information is available regarding the raiding behavior in nature of dulotic ants belonging to the tribeLeptothoracini. Between July 17 and 24, 1991, several raids ofChalepoxenus muellerianus (Finzi) were observed in nature near Tignale/Lago di Garda, Italy. Apparently, this species raids frequently during its summer raiding season (5 raids were observed during 7 days spent observing 8 colonies). A singleChalepoxenus colony sometimes raids more than one host colony more or less simultaneously. Observations during which oneChalepoxenus colony raided another and captured slavemaker brood indicate that intraspecific raids can occur either accidentally, or as a result of competition or territoriality when there is a sufficient dense slavemaker population.