Molecular phylogeny of Vespidae (Hymenoptera) and the evolution of sociality in wasps

Characterization of Complete Mitochondrial Genome and Phylogenetic Analysis of a Nocturnal Wasps-Provespa barthelemyi (Hymenoptera: Vespidae)

Genus Provespa contains nocturnal wasps mainly found in the southeastern region of Asia. There are no complete genome resources available of this genus, which hinders the study of its phylogenetic evolution and the origin of nocturnal behavior in the Vespidae family. Through high-throughput sequencing, we obtained the mitochondrial genome of Provespa barthelemyi (Hymenoptera: Vespidae), which is 17,721 base pairs in length and contains 13 protein-coding genes (PCGs), 22 tRNAs, and two rRNAs. We identified four gene rearrangement events of P. barthelemyi that frequently occur in the Vespidae family. We used Maximum Likelihood (ML) methodologies to construct a phylogenetic tree based on the sequenced mitochondrial genome and the available data of reported species belonging to Vespinae. Our findings confirmed the monophyly of Vespinae. Our study reports the first complete mitochondrial genome of Provespa and compares its characteristics with other mitochondrial genomes in the family Vespidae. This research should shed light on the phylogenetic relationships and ecological characteristics of the Vespidae family.

Species morphospace boundary revisited through wing phenotypic variations of Antodynerus species (Hymenoptera: Vespidae: Eumeninae) from the Indian subcontinent

The main objective of this study was to investigate the taxonomic significance of wing phenotypic variations (size and shape) for classifying potter wasps. This is the first study investigating the wing size and shape variations, as well as wing asymmetry, sexual dimorphism, wing integration, and phylogenetic signal analysis of all known Antodynerus species from the Indian subcontinent: A. flavescens, A. limbatus, and A. punctatipennis. We used forewings and hindwings for geometric morphometric analysis, and we proved that each species’ wing had unique size and shape variations, as well as significant right–left wing asymmetry and sexual dimorphism across the Antodynerus species, as verified by discriminant function analysis. Wings of Vespidae are longitudinally folded; based on that, we tested two alternative wing modular hypotheses for evaluating the wing integration, using two subsets organization, such as anterior–posterior (AP) and proximal-distal (PD) wing modular organization. We proved that Antodynerus species wings are highly integrated units (RV > 0.5), and we rejected our hypothesis at p < 0.05. The morphospace distribution analysis revealed that each species has its unique morphospace boundary, although they share some level of homoplasy, which suggests to us that we can use wing morphometric traits for Antodynerus species delimitation. In addition, we revealed the phylogenetic signal of Antodynerus species. Surprisingly, we found a shape-related phylogenetic signal in the forewing, and there is no significant (p > 0.05) phylogenetic signal in forewing size, hindwing shape, and size. We observed that the Antodynerus species’ forewing shape is evolutionarily more highly constrained than the hindwing. We found that A. limbatus and A. flavescens with distinct geographical distribution share a similar evolutionary history, while A. punctatipennis evolved independently.

Next-Generation Sequencing of Four Mitochondrial Genomes of Dolichovespula (Hymenoptera: Vespidae) with a Phylogenetic Analysis and Divergence Time Estimation of Vespidae

The wasp genus Dolichovespula (Hymenoptera: Vespidae: Vespinae) is a eusocial wasp group. Due to the taxonomic and phylogenetic issues with the family Vespidae, more genetic data should be gathered to provide efficient approaches for precise molecular identification. For this work, we used next-generation sequencing (also known as high-throughput sequencing) to sequence the mitochondrial genomes (mtgenomes) of four Dolichovespula species, viz. D. flora, D. lama, D. saxonica, and D. xanthicincta 16,064 bp, 16,011 bp, 15,682 bp, and 15,941 bp in length, respectively. The mitochondrial genes of the four species are rearranged. The A + T content of each mtgenome is more than 80%, with a control region (A + T-rich region), 13 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes. There are 7 to 11 more genes on the majority strands than on the minority strands. Using Bayesian inference and Maximum-Likelihood methodologies as well as data from other species available on GenBank, phylogenetic trees and relationship assessments in the genus Dolichovespula and the family Vespidae were generated. The two fossil-based calibration dates were used to estimate the origin of eusociality and the divergence time of clades in the family Vespidae. The divergence times indicate that the latest common ancestor of the family Vespidae appeared around 106 million years ago (Ma). The subfamily Stenogastrinae diverged from other Vespidae at about 99 Ma, the subfamily Eumeninae at around 95 Ma, and the subfamily Polistinae and Vespinae diverged at approximately 42 Ma. The genus Dolichovespula is thought to have originated around 25 Ma. The origin and distribution pattern of the genus Dolichovespula are briefly discussed.

First Comprehensive Analysis of Both Mitochondrial Characteristics and Mitogenome-Based Phylogenetics in the Subfamily Eumeninae (Hymenoptera: Vespidae)

The subfamily Eumeninae plays a significant role in the biological control of agricultural pests. However, the characteristics of eumenine mitogenomes that are important molecular markers for phylogenetics are not clearly revealed. Here, 52 eumenine mitogenomes are newly sequenced and annotated, and the phylogenetic relationships of the subfamily are comprehensively analyzed based on 87 vespid mitogenomes. Through the comparative analysis of the 54 eumenine mitogenomes, the gene compositions of about one half of the 54 species match with ancestral insect mitogenome, and remaining others contain two trnM which are highly similar, with 51.86% (Eumenes tripunctatus) to 90.65% (Pseumenes nigripectus) sequence identities, which is unique among the reported mitogenomes of the family Vespidae. Moreover, the translocation trnL1 upstream of nad1 is a common rearrangement event in all eumenine mitogenomes. The results of phylogenetic analyses support the paraphyly of the subfamily Eumeninae and the tribe Odynerini, respectively, and the monophyly of the tribe Eumenini, and verify that the tribe Zethini is a valid subfamily Zethinae. In this study, the relationships between some genera such as Allorhynchium and Pararrhynchium or the taxonomic status of the subgenera such as Eremodynerus and Dirhynchium are found to be confusing and there should be further inquiry with more samples.

Linking the Morphology of Sternal Glands to Rubbing Behavior by Vespa soror (Hymenoptera: Vespidae) Workers During Recruitment for Group Predation

The activities of social insect colonies are supported by exocrine glands and the tremendous functional diversity of the compounds that they secrete. Many social wasps in the subfamilies Vespinae and Polistinae have two sternal glands-the van der Vecht and Richards' glands-that vary in their features and function across the species in which they are found. Field observations suggest that giant hornets use secretions from the van der Vecht gland to chemically mark targeted nests when workers initiate group attacks on social insect prey. However, descriptions of giant hornets' sternal glands and details about their recruitment behavior are lacking. We describe the morphology of the sternal glands of the giant hornet Vespa soror du Buysson and consider their potential to contribute to a marking pheromone. We also assess the gastral rubbing behavior of workers as they attacked Apis cerana F. (Hymenoptera: Apidae) colonies. V. soror workers have well-developed van der Vecht and Richards' glands on their terminal gastral sternites, with morphologies that robustly support the synthesis, storage, and dissemination of their secretory products. Observations confirm that the van der Vecht gland is exposed during gastral rubbing, but that the Richards' gland and glands associated with the sting apparatus may also contribute to a marking pheromone. Workers briefly but repeatedly rubbed their gasters around hive entrances and on overhead vegetation. Colonies were heavily marked over consecutive attacks. Our findings provide insight into the use of exocrine secretions by giant hornets as they recruit nestmates to prey colonies for group attacks.

The first divergence time estimation of the subfamily Stenogastrinae (Hymenoptera: Vespidae) based on mitochondrial phylogenomics

In this study, the mitochondrial genomes of three Stenogastrinae species, Eustenogaster scitula, Liostenogaster nitidipennis and Parishnogaster mellyi were sequenced and annotated, and a total of 16 vespid mtgenomes are comparatively analyzed. Our results indicate that codon usage bias is mainly dominated by mutational pressure, and affected only slightly by natural selection. Selective pressure analysis of protein-coding genes (PCGs) shows that the highest evolutionary rate is present in NADH complex I, and the lowest in cox1. Compared with the reported mtgenomes of other Vespidae, in Stenogastrinae, trnH is shifted to a new position. Phylogenetic analyses are performed using Bayesian method and Maximum Parsimony. Phylogenetic analysis further confirms that the Stenogastrinae is the sister group of all remaining Vespidae. Divergence time of Stenogastrinae from other Vespidae is estimated at ~ 166 Mya. Our results also support that eusociality evolved twice in the family Vespidae.

Phylogenomic Evidence Overturns Current Conceptions of Social Evolution in Wasps (Vespidae)

The hypothesis that eusociality originated once in Vespidae has shaped interpretation of social evolution for decades and has driven the supposition that preimaginal morphophysiological differences between castes were absent at the outset of eusociality. Many researchers also consider casteless nest-sharing an antecedent to eusociality. Together, these ideas endorse a stepwise progression of social evolution in wasps (solitary → casteless nest-sharing → eusociality with rudimentary behavioral castes → eusociality with preimaginal caste-biasing (PCB) → morphologically differentiated castes). Here, we infer the phylogeny of Vespidae using sequence data generated via anchored hybrid enrichment from 378 loci across 136 vespid species and perform ancestral state reconstructions to test whether rudimentary and monomorphic castes characterized the initial stages of eusocial evolution. Our results reject the single origin of eusociality hypothesis, contest the supposition that eusociality emerged from a casteless nest-sharing ancestor, and suggest that eusociality in Polistinae + Vespinae began with castes having morphological differences. An abrupt appearance of castes with ontogenetically established morphophysiological differences conflicts with the current conception of stepwise social evolution and suggests that the climb up the ladder of sociality does not occur through sequential mutation. Phenotypic plasticity and standing genetic variation could explain how cooperative brood care evolved in concert with nest-sharing and how morphologically dissimilar castes arose without a rudimentary intermediate. Furthermore, PCB at the outset of eusociality implicates a subsocial route to eusociality in Polistinae + Vespinae, emphasizing the role of mother-daughter interactions and subfertility (i.e. the cost component of kin selection) in the origin of workers.

Molecular phylogeny of Orthetrum dragonflies reveals cryptic species of Orthetrum pruinosum

Dragonflies of the genus Orthetrum are members of the suborder Anisoptera, family Libellulidae. There are species pairs whose members are not easily separated from each other by morphological characters. In the present study, the DNA nucleotide sequences of mitochondrial and nuclear genes were employed to elucidate the phylogeny and systematics of Orthetrum dragonflies. Phylogenetic analyses could not resolve the various subfamilies of the family Libellulidae unequivocally. The nuclear 28S rRNA gene is highly conserved and could not resolve congeneric species of Orthetrum. Individual mitochondrial genes (COI, COII, and 16S rRNA) and combination of these genes as well as the nuclear ITS1&2 genes clearly differentiate morphologically similar species, such as the reddish species pairs O. chrysis and O. testaceum, and the bluish-coloured species O. glaucum and O. luzonicum. This study also reveals distinct genetic lineages between O. pruinosum schneideri (occurring in Malaysia) and O. pruinosum neglectum (occurring north of Peninsular Malaysia from India to Japan), indicating these taxa are cryptic species.

Distinct genetic clades of Malaysian Copera damselflies and the phylogeny of platycnemine subfamilies

The phylogenetic relationships of some taxa in the Platycnemidinae at the species and generic levels have been investigated. Phylogenetic trees were generated from both individual mitochondrial encoded COI, COII, 16S rDNA and nuclear encoded 28S rDNA and also combined sequences; these data indicate that the component taxa of the genus Copera belong to two distinct genetic clades - the marginipes group and the annulata group. There was no distinct genetic difference between the red-legged and yellow-legged morphs of C. vittata. Molecular data showed that the annulata group is considered a member of the genus Platycnemis, as originally proposed. The genus Coeliccia, a member of the subfamily Calicnemiinae (Platycnemididae), is not grouped with the Platycnemidinae. The Disparoneurinae of the 'Protoneuridae' showed a closer relationship to the Platycnemidinae than the Calicnemiinae. The dataset supports the placement of the Disparoneurinae as a subfamily of the Platycnemididae. This resolves the monophyly of Platycnemididae.

Mitochondrial genome organization and phylogeny of two vespid wasps

We sequenced the entire mitochondrial genome of Abispa ephippium (Hymenoptera: Vespoidea: Vespidae: Eumeninae) and most of the mitochondrial genome of Polistes humilis synoecus (Hymenoptera: Vespoidea: Vespidae: Polistinae). The arrangement of genes differed between the two genomes and also differed slightly from that inferred to be ancestral for the Hymenoptera. The genome organization for both vespids is different from that of all other mitochondrial genomes previously reported. A number of tRNA gene rearrangements were identified that represent potential synapomorphies for a subset of the Vespidae. Analysis of all available hymenopteran mitochondrial genome sequences recovered an uncontroversial phylogeny, one consistent with analyses of other types of data.

Origins of asexuality in Bryobia mites (Acari: Tetranychidae)

Background

Obligate asexual reproduction is rare in the animal kingdom. Generally, asexuals are considered evolutionary dead ends that are unable to radiate. The phytophagous mite genus Bryobia contains a large number of asexual species. In this study, we investigate the origin and evolution of asexuality using samples from 111 populations in Europe, South Africa and the United States, belonging to eleven Bryobia species. We also examine intraspecific clonal diversity for one species, B. kissophila, by genotyping individuals from 61 different populations. Knowledge on the origin of asexuality and on clonal diversity can contribute to our understanding of the paradox of sex.

Results

The majority (94%) of 111 sampled populations reproduces asexually. Analysis of part of nuclear 28S rDNA shows that these asexuals do not form a monophyletic clade. Analysis of the mitochondrial COI region shows that intraspecific variation is extensive (up to 8.8%). Within B. kissophila, distinct clades are found, which are absent at the nuclear 28S rDNA level. Moreover, paraphyletic patterns are found at the mitochondrial DNA.

Conclusion

Asexuality is widespread in the genus Bryobia, signifying that some animal taxa do contain a high number of asexuals. We argue that asexuality originated multiple times within Bryobia. Wolbachia bacteria cause asexuality in at least two Bryobia species and may have infected different species independently. The high intraspecific clonal diversity and the patterns of paraphyly at the mitochondrial DNA in B. kissophila might be explained by a high mutation fixation rate and past hybridization events. Reproductive parasites like Wolbachia and Cardinium might influence these processes. We discuss the role these bacteria could play in the evolutionary success of asexual species.

R, Quicke DLJ. Molecular phylogeny and historical biogeography of the cosmopolitan parasitic wasp subfamily Doryctinae (Hymenoptera:Braconidae)

The phylogenetic relationships among representatives of 64 genera of the cosmopolitan parasitic wasps of the subfamily Doryctinae were investigated based on nuclear 28S ribosomal (r) DNA (~650 bp of the D2–3 region) and cytochrome c oxidase I (COI) mitochondrial (mt) DNA (603 bp) sequence data. The molecular dating of selected clades and the biogeography of the subfamily were also inferred. The partitioned Bayesian analyses did not recover a monophyletic Doryctinae, though the relationships involved were only weakly supported. Strong evidence was found for rejecting the monophylies of both Doryctes Haliday, 1836 and Spathius Nees, 1818. Our results also support the recognition of the Rhaconotini as a valid tribe. A dispersal–vicariance analysis showed a strong geographical signal for the taxa included, with molecular dating estimates for the origin of Doryctinae and its subsequent radiation both occurring during the late Paleocene–early Eocene. The divergence time estimates suggest that diversification in the subfamily could have in part occurred as a result of continental break-up events that took place in the southern hemisphere, though more recent dispersal events account for the current distribution of several widespread taxa.

Multigene phylogeny reveals eusociality evolved twice in vespid wasps

Eusocial wasps of the family Vespidae are thought to have derived their social behavior from a common ancestor that had a rudimentary caste-containing social system. In support of this behavioral scenario, the leading phylogenetic hypothesis of Vespidae places the eusocial wasps (subfamilies Stenogastrinae, Polistinae, and Vespinae) as a derived monophyletic clade, thus implying a single origin of eusocial behavior. This perspective has shaped the investigation and interpretation of vespid social evolution for more than two decades. Here we report a phylogeny of Vespidae based on data from four nuclear gene fragments (18S and 28S ribosomal DNA, abdominal-A and RNA polymerase II) and representatives from all six extant subfamilies. In contrast to the current phylogenetic perspective, our results indicate two independent origins of vespid eusociality, once in the clade Polistinae+Vespinae and once in the Stenogastrinae. The stenogastrines appear as an early diverging clade distantly related to the vespines and polistines and thus evolved their distinctive form of social behavior from a different ancestor than that of Polistinae+Vespinae. These results support earlier views based on life history and behavior and have important implications for interpreting transitional stages in vespid social evolution.

Monophyly and phylogenetic relationships of Thereva and therevine genus-groups (Insecta:Diptera:Therevidae) based on EF-1α, 28S rDNA and mitochondrial 16S rDNA sequences

Phylogenetic analyses using 28S rDNA, elongation factor (EF)-1α, and mt 16S rDNA sequences were performed to test the monophyly of Thereva Latreille. Two of the three Afrotropical Thereva species groups lack the genitalia characters that unambiguously diagnose Thereva in the Holarctic Region, but phylogenetic relationships among Thereva species groups and therevine genera are poorly understood. Using an extensive taxonomic sample (39 of the 62 therevine genera) and Thereva, sensu lato (15 spp.), simultaneous analyses of all three gene partitions recovered Nearctic and Palaearctic Thereva species in a well supported clade that includes the Afrotropical seminitida-group but excludes the Afrotropical analis- and turneri-groups. Stronger phylogenetic signal from the EF-1α partition, measured by the skewness statistic and proportion of total parsimony informative characters, dominated conflicting signal from the 16S partition and weaker, but more congruent, signal from 28S. Reducing the taxonomic sample in analyses of Therevinae reduced homoplasy, increased phylogenetic structure and partitioned Bremer support values and reduced incongruence with 28S for the 16S partition. Although molecular analyses yielded partial recovery of informal therevine genus-groups, morphological diagnoses of higher-level groups are poorly supported with the exception of Cyclotelini. The ‘Holarctic radiation’ refers to a diverse clade of genera closely related to Pandivirilia Irwin & Lyneborg and Acrosathe Irwin & Lyneborg widely distributed throughout the Holarctic Region that is the sister-group to Thereva, sensu stricto. Results from these analyses underscore the importance of male and female genitalia characters in recognising monophyletic groups and regional endemism in therevine diversification.

The structure of a single unit of ribosomal RNA gene (rDNA) including intergenic subrepeats in the Australian bulldog ant Myrmecia croslandi (Hymenoptera: Formicidae)

A complete single unit of a ribosomal RNA gene (rDNA) of M. croslandi was sequenced. The ends of the 18S, 5.8S and 28S rRNA genes were determined by using the sequences of D. melanogaster rDNAs as references. Each of the tandemly repeated rDNA units consists of coding and non-coding regions whose arrangement is the same as that of D. melanogaster rDNA. The intergenic spacer (IGS) contains, as in other species, a region with subrepeats, of which the sequences are different from those previously reported in other insect species. The length of IGSs was estimated to be 7-12 kb by genomic Southern hybridization, showing that an rDNA repeating unit of M. croslandi is 14-19 kb-long. The sequences of the coding regions are highly conserved, whereas IGS and ITS (internal transcribed spacer) sequences are not. We obtained clones with insertions of various sizes of R2 elements, the target sequence of which was found in the 28S rRNA coding region. A short segment in the IGS that follows the 3' end of the 28S rRNA gene was predicted to form a secondary structure with long stems.

The phylogeny of the social wasp subfamily Polistinae: evidence from microsatellite flanking sequences, mitochondrial COI sequence, and morphological characters

BACKGROUND

Social wasps in the subfamily Polistinae (Hymenoptera: Vespidae) have been important in studies of the evolution of sociality, kin selection, and within colony conflicts of interest. These studies have generally been conducted within species, because a resolved phylogeny among species is lacking. We used nuclear DNA microsatellite flanking sequences, mitochondrial COI sequence, and morphological characters to generate a phylogeny for the Polistinae (Hymenoptera) using 69 species.

RESULTS

Our phylogeny is largely concordant with previous phylogenies at higher levels, and is more resolved at the species level. Our results support the monophyly of the New World subgenera of Polistini, while the Old World subgenera are a paraphyletic group. All genera for which we had more than one exemplar were supported as monophyletic except Polybia which is not resolved, and may be paraphyletic.

CONCLUSION

The combination of DNA sequences from flanks of microsatellite repeats with mtCOI sequences and morphological characters proved to be useful characters establishing relationships among the different subgenera and species of the Polistini. This is the first detailed hypothesis for the species of this important group.

Molecular phylogenetic analysis of ant subfamily relationship inferred from rDNA sequences

The relationships among ant subfamilies were studied by phylogenetic analysis of rDNA sequences of 15 species from seven subfamilies. PCR primers were designed on the basis of the rDNA sequence of the Australian bulldog ant, Myrmecia croslandi, previously determined. Phylogenetic trees were constructed using sequences of a fragment of 18S rDNA (1.8 kb), a fragment of 28S rDNA (0.7 kb excluding variable regions) and a combination of the 18S and 28S rDNAs, by neighbor-joining (NJ), maximum parsimony (MP) and maximum likelihood (ML). rDNA sequences corresponding to the same fragments from three non-ant hymenopteran species (a sawfly, a bee and a wasp) were employed as outgroups. These trees indicated that the ant subfamilies were clustered singly, and, among the seven subfamilies examined, Ponerinae and six other subfamilies are in a sister-groups relationship. The relationship among the six subfamilies, however, was not clarified. The phylogenetic trees constructed in the present study are not in contradiction to the tree from cladistic analysis of morphological data by Baroni Urbani et al. (1992) and the tree from morphological and molecular data (Ward and Brady, 2003), but are inconsistent with the traditional phylogeny. The present results thus raise a question as to the status of some traditionally employed "key" morphological characters. The present results also call for a reexamination of Amblyopone traditionally treated as a member of Ponerinae as belonging to a new subfamily.

Nestmate recognition in Parischnogaster striatula (Hymenoptera Stenogastrinae), visual and olfactory recognition cues

The recognition of nestmates from alien individuals is a well known phenomenon in social insects. In the stenogastrine wasp Parischnogaster striatula, we investigated the ability of females to recognize nestmates and the cues on which such recognition is based. Recognition of nestmates was observed in naturally occurring interactions between wasps approaching a nest and the resident females on that nest. This recognition was confirmed in experiments in which nestmates or alien conspecifics were presented to resident females. In naturally occurring interactions, nestmates generally approach their nest with a direct flight, while aliens usually hover in front of the nest before landing. In experiments in which the presented wasps were placed close to the nest in a direct manner, antennation of the presented wasp generally occurred, indicating that chemical cues are involved. Experiments in which dead alien individuals, previously washed in hexane, and then reapplied with extracts were recognized by colonies giving further evidence that chemical cues mediate nestmate recognition. Epicuticular lipids, known to be nestmate recognition cues in social insects, were chemically analysed by GC-MS for 44 P. striatula females from two different populations (13 different colonies). Discriminant analysis was performed on the data for the lipid mixture composition. The discriminant model showed that, in the samples from these two populations, 68.2% and 81.9% of the specimens could be correctly assigned to their colony.

The evolution of color vision in insects

We review the physiological, molecular, and neural mechanisms of insect color vision. Phylogenetic and molecular analyses reveal that the basic bauplan, UV-blue-green-trichromacy, appears to date back to the Devonian ancestor of all pterygote insects. There are variations on this theme, however. These concern the number of color receptor types, their differential expression across the retina, and their fine tuning along the wavelength scale. In a few cases (but not in many others), these differences can be linked to visual ecology. Other insects have virtually identical sets of color receptors despite strong differences in lifestyle. Instead of the adaptionism that has dominated visual ecology in the past, we propose that chance evolutionary processes, history, and constraints should be considered. In addition to phylogenetic analyses designed to explore these factors, we suggest quantifying variance between individuals and populations and using fitness measurements to test the adaptive value of traits identified in insect color vision systems.

Use of Dufour's gland secretion in nest defence and brood nutrition by hover wasps (Hymenoptera, Stenogastrinae)

Social wasps of the subfamily Stenogastrinae produce an abdominal secretion that is used in two distinct biological contexts. First, the secretion plays an important role in larval nutrition where it serves as a substrate in which food is placed by the adults for eventual consumption by the larvae. Second, in several species, females apply the same secretion to the substrate on which their nests are constructed, where it constitutes a sticky barrier that defends the immature brood from predation by ants. This paper describes for the first time ant guard construction behaviour of three species of stenogastrine wasps belonging to the genera Eustenogaster and Liostenogaster. The identification of compounds making up these secretions was also performed by gas chromatography-mass spectrometry. Ant guards and brood secretions were similar, with saturated and unsaturated long chain hydrocarbons and alcohols as major components. We further confirm that the glandular source of abdominal secretion is the Dufour's gland. This gland contains the same hydrocarbons, and in the same proportions as ant guards and brood secretion. We discuss the fundamental importance of Dufour's gland secretion in the social life of these wasps by comparing species with and without ant guards within the subfamily.

The current state of insect molecular systematics: a thriving Tower of Babel

Insect molecular systematics has undergone remarkable recent growth. Advances in methods of data generation and analysis have led to the accumulation of large amounts of DNA sequence data from most major insect groups. In addition to reviewing theoretical and methodological advances, we have compiled information on the taxa and regions sequenced from all available phylogenetic studies of insects. It is evident that investigators have not usually coordinated their efforts. The genes and regions that have been sequenced differ substantially among studies and the whole of our efforts is thus little greater than the sum of its parts. The cytochrome oxidase I, 16S, 18S, and elongation factor-1 alpha genes have been widely used and are informative across a broad range of divergences in insects. We advocate their use as standards for insect phylogenetics. Insect molecular systematics has complemented and enhanced the value of morphological and ecological data, making substantial contributions to evolutionary biology in the process. A more coordinated approach focused on gathering homologous sequence data will greatly facilitate such efforts.

A comparison of the composition of silk proteins produced by spiders and insects

Proteins that are highly expressed and composed of amino acids that are costly to synthesize are likely to place a greater drain on an organism's energy resources than proteins that are composed of ingested amino acids or ones that are metabolically simple to produce. Silks are highly expressed proteins produced by all spiders and many insects. We compared the metabolic costs of silks spun by arthropods by calculating the amount of ATP required to produce their component amino acids. Although a definitive conclusion requires detailed information on the dietary pools of amino acids available to arthropods, on the basis of the central metabolic pathways, silks spun by herbivorous, Lepidoptera larvae require significantly less ATP to synthesize than the dragline silks spun by predatory spiders. While not enough data are available to draw a statistically based conclusion, comparison of homologous silks across ancestral and derived taxa of the Araneoidea seems to suggest an evolutionary trend towards reduced silk costs. However, comparison of the synthetic costs of dragline silks across all araneomorph spiders suggests a complicated evolutionary pattern that cannot be attributed to phylogenetic position alone. We propose that the diverse silk-producing systems of the araneoid spiders (including three types of protein glues and three types of silk fibroin), evolved through intra-organ competition and that taxon-specific differences in the composition of silks drawn from homologous glands may reflect limited or fluctuating amino acid availability. The different functional properties of spider silks may be a secondary result of selection acting on different polypeptide templates.