Tachinid (Diptera, Tachinidae) parasitoids of sawflies (Hymenoptera, Symphyta)

A list of 31 genera of tachinid parasitoids of sawflies is given. Despite the ecological and habitual similarity of sawflies and Lepidoptera, utilization of sawflies by tachinids was not as successful from the evolutionary point of view as utilization of Lepidoptera. Parasitism of tachinids in sawflies is evidently secondary; it appeared repeatedly and originates from parasitism in Lepidoptera. Most genera of tachinids are polyphagous. Endoparasitic Hymenoptera are koinobionts similarly to tachinids. The direct contact of the parasitoid with active mobile host larva not only results in complication of behavior and its specialization, but also promotes formation of different morphological innovations faster than that in idiobionts.     

Seasonal flight activity of sawflies (Hymenoptera, Symphyta) in submontane region of the Western Carpathians, Central Slovakia

Species representation and seasonality of adult sawflies (Symphyta) were studied using Malaise traps at three submontane study sites (Hriňová — HR, Mošovce — MO and Štefanová — ŠT) in the Western Carpathians (Central Slovakia). One trap was operated at each study site continuously during the growing season, in MO in 1992, in HR in 1995 and in ŠT in 1996. A total of 9,281 adults representing 244 species in 9 families were collected. Very rich sawfly assemblages were found. The highest species richness was in MO (181 species), followed by ŠT (153 species) and HR (118 species). Pseudodineura fuscula was recorded from Slovakia for the first time. Adults were present in traps from the end of April through the first half of October. Most species occurred from the second half of May through the first half of June and finished flight activity by the end of June. Seasonal flight activities of the 16 most abundant species are analysed and discussed.     

An apterous female sawfly (Hymenoptera: Symphyta) from Papua New Guinea

Abstract. A new species of sawfly, Cladomacra terricola , belonging to the family Pergidae, is described from an apterous female from mid-montane Papua New Guinea. The profoundly modified thorax of the female is compared with the thorax of other wing-reduced and macropterous Hymenoptera. The ovipositor is greatly reduced and lacks the typical, symphytan, saw-like valves. The ordinal, family, subfamily and generic classification of C. terricola is discussed. Diagnostic features of the pergid subfamilies Pterygophorinae, Euryinae and Perreyiinae are reviewed. The egg and larva of C. terricola are described. Egg brooding by the female is reported. Larvae of C. terricola may feed on dead plant material in forest litter.     

Host plant adaptations in myrtaceous-feeding Pergid sawflies: essential oils and the morphology and behaviour of Pergagrapta larvae (Hymenoptera, Symphyta, Pergidae)

Australian pergine sawflies typically feed on eucalypts and other closely-related Myrtaceae, which are known for their high content of essential oils. We describe a novel morphological adaptation of the inner mandibular surface of larval stage Pergagrapta species, which feed on leaves of Melaleuca quinquenervia (Myrtaceae). This 'scopa mandibularis' forms an extensive mesh of setaceous papillae on what is usually the grinding surface of the mandible. Behavioural, chemical and morphological investigations of the sawfly- Melaleuca system suggest that the scopa may function in the physical separation of toxic leaf oils from the diet. The oils are stored in a pharyngeal diverticulum from where they are ejected under two circumstances. Oil from the diverticulum is voided prior to feeding and/or during feeding at night, which indicates a mechanism to eliminate host-associated oils. Larvae rest in close aggregations during the day, when they retain a full diverticulum, but the oils may be emitted for defensive purposes when larvae are disturbed. Chemical evidence suggests that 1,8-cineole, the major component in the M. quinquenervia leaves, is selectively metabolized to a more soluble hydroxycineole. We postulate that the separation and regurgitation of oils is not only a defence mechanism against predators, as usually stated, but also a mechanism by which pergid larvae eliminate oils from their diet, to reduce the toxicity of their food plants.     

Web-spinning sawflies of the sylvaticus-group of Pamphilius (Hymenoptera: Pamphiliidae)

Abstract The Pamphilius sylvaticus group is redefined to include seventeen species in the Holarctic: sylvaticus (Linnaeus), fumipennis (Curtis) and nemorum (Gmelin) from Europe; alnicola Ermolenko, daisenus Takeuchi, volatilis (Smith), benesi sp.n., gracilis sp.n., japoni-cus sp.n. and montanus sp.n. from northeastern Asia (mainly Japan); burquei (Provancher), cinctus Harrington, middlekauffi Shinohara & Smith, ocreatus (Say), rileyi (Cresson) and semicinctus (Norton) from eastern N. America; and persicum MacGillivray from eastern N. America and the Caucasus. Each species is described and figured and a key for identification is given.     

Giant sawflies and their kin: morphological phylogeny of Cimbicidae (Hymenoptera)

The Cimbicidae is a small family including the largest extant true sawflies (Tenthredinoidea). It comprises four subfamilies, three of which have a northern hemisphere distribution (Abiinae, Cimbicinae – Holarctic/Oriental; Corynidinae – Palaearctic), whereas the Pachylostictinae are restricted to South America. No previous attempts have been made to evaluate the subfamily classification in a cladistic context. In the present paper, 144 morphological characters from the adult anatomy for a total of 95 species of Cimbicidae and 26 outgroup taxa are scored. All subfamilies and all genera of Cimbicidae except one are represented; all families of Tenthredinoidea are represented in the outgroup. Equal weights (EW) and implied weights (IW) analyses are conducted in tnt . The results largely corroborate the existing subfamily classification, except for Pachylostictinae which are paraphyletic in IW analyses with low K‐values. Abiinae + Cimbicinae is always retrieved and strongly supported; Corynidinae + Pachylostictinae is retrieved in most analyses but weakly supported. Revised diagnoses of the subfamilies are provided. Several genera are retrieved as monophyletic, notable exceptions being Praia and Trichiosoma, which are polyphyletic. The evolution of large body size in Cimbicidae is briefly discussed; possible related phenomena are intrasexual competition and mimicry, i.e. resemblance to large apids or vespids.     

Variations in silk gland morphology among sawfiy larvae (Hymenoptera: Symphyta)

An account is given of the occurrence of different types of secretory cell and storage reservoir in the larvae of 45 species of Symphyta.     

Revision of the Australasian genus Orussobaius Benson (Hymenoptera: Symphyta: Orussidae)

Abstract The Australasian genus Orussobaius Benson is revised. Seven species are recognised: Orussobaius paniculus sp. n. from Papua New Guinea, and six species from Australia: O. badius sp. n., O. caligneus sp. n., O. mesembrinus Benson, O. minutissimus sp. n., O. minutus Benson, and O. wilsoni Benson. Orussobaius normani Rayment (new synonymy) is removed from synonymy with O. wilsoni and treated as a junior synonym of O. minutus instead. With a body length of only 2 mm, O. minutissimus sp. n. is the smallest currently known sawfly species in the world. A key is provided and distribution maps are shown for all species. The genus Orussobaius is redefined on the basis of all species currently included.     

Morphology of the pretarsus of the sawflies and horntails (Hymenoptera: 'Symphyta')

The pretarsal structures have been studied in representatives of 13 families of 'Symphyta' by means of light microscopy. The pretarsal sclerites (manubrium, planta, and unguitractor) vary in shape among different families. The shape of the manubrium is triangular in representatives of Xyelidae and Orussidae and bifurcated in those of Tenthredinoidea. For representatives of Siricomorpha, an elongated shape of the manubrium is typical with such variations, as distally expanded, proximally expanded, clavate, spear-shaped. Plantae of different Symphyta vary in shape and level of sclerotization. In representatives of Siricidae, the female manubrium and arolium are significantly reduced, and arcus and dorsal plates are completely absent. Siricid males possess all pretarsal sclerites and a well-developed arolium. Auxiliary sclerites are absent in representatives of Orussidae. Trichoid sensilla are absent on the plantae in representatives of Cephidae and Orussidae. Other studied Symphyta possess two trichoid sensilla on the planta. Representatives of all investigated families bear two campaniform sensilla on the manubrium, with the exception of Siricidae having three sensilla. Kinematics of the pretarsus with bifurcated manubrium are modeled and discussed.     

Evolution of gall morphology and host-plant relationships in willow-feeding sawflies (Hymenoptera: Tenthredinidae)

Abstract.— There are over 200 species of nematine sawflies that induce galls on willows (Salix spp.). Most of the species are monoor oligophagous, and they can be separated into seven or eight different groups based on the type of gall that they induce. We studied the evolution of different gall types and host plant associations by reconstructing the phylogeny of five outgroup and 31 ingroup species using DNA sequence data from the mitochondrial cytochrome b gene. Maximum-parsimony and maximum-likelihood analyses resulted in essentially the same phylogeny with high support for important branches. The results show that: (1) the galling species probably form a monophyletic group; (2) true closed galls evolved only once, via leaf folders; (3) with the possible exception of leaf rollers, all gall type groups are mono- or paraphyletic; (4) similar gall types are closer on the phylogeny than would be expected by a random process; (5) there is an apparent evolutionary trend in galling site from the leaf edge towards the more central parts of the host plant; and (6) many willow species have been colonized several times, which excludes the possiblity of parallel cladogenesis between willows and the gallers; however, there are signs of restrictions in the evolution of host use. Many of the patterns in the evolutionary history of nematine gallers have also been observed in earlier studies on other insect gallers, indicating convergent evolution between the independent radiations.     

Host plant influence on chemical defense in conifer sawflies (Hymenoptera: Diprionidae)

Host diet affects the defensive efficacy of Neodiprion sawflies. In laboratory assays with wood ants (Formica obscuripes), secretions from larvae reared on Pinus banksiana were the most repellent, while those from P. resinosa feeders were the least so. This was explained diterpene resin acid content, but not total monoterpene content. The terpene content of regurgitant generally reflected dietary concentrations. Compounds were sequestered nonselectively by larvae. Host-based differences in defense persisted at the behavioral level. P. banksiana feeders regurgitated greater volumes of fluid and were less likely to be disabled or killed by ants in one-on-one interactions than were larvae fed on P. resinosa. The defensive advantages of host diet conflicted with developmental requirements. N. sertifer reared on P. banksiana (the best diet for defense in all cases) had lower cocoon weights (a correlate of fecundity) than those reared on other diets, and had prolonged larval development compared to insects fed P. sylvestris. No such tradeoff was detected in N. lecontei. Larvae of both species strongly preferred P. banksiana over P. resinosa in feeding choice assays.     

Phylogenetics and evolution of host-plant use in leaf-mining sawflies (Hymenoptera: Tenthredinidae: Heterarthrinae)

The habit of mining within leaves has evolved convergently in numerous plant-feeding insect taxa. Many leaf-mining groups contain a large number of species with distinct feeding preferences, which makes them highly suitable for studies on the evolutionary history of host-plant use and on the role of niche shifts in speciation. We aimed to clarify the origin, classification, and ecological evolution of the tenthredinid sawfly subfamily Heterarthrinae, which contains c. 150 leaf-mining species that collectively feed on over 20 plant genera around the world. For this, we reconstructed the phylogeny of representative heterarthrine species and diverse outgroups from the superfamily Tenthredinoidea on the basis of DNA sequence data collected from two mitochondrial (CoI and Cytb) and two nuclear (EF-1α and NaK) genes. Thereafter, we inferred the history of niche diversification within Heterarthrinae by plotting larval host-plant associations on the trees, and by contrasting a time-calibrated leaf-miner phylogeny with the phylogeny of their host plants. The results show that: (1) heterarthrine leaf-miners constitute a monophyletic group that arose from external-feeding blennocampine lineages within the Tenthredinidae c. 110-80 million years ago; (2) heterarthrines generally radiated well after their host taxa, and extant host-plant associations therefore result from a combination of host conservatism and occasional shifts among available plant taxa; and (3) diversification in Heterarthrinae apparently occurs by multiple mechanisms, including sympatric or allopatric ecological speciation, non-ecological allopatric speciation, and possibly allochronic speciation. Overall, both present and historical host-use patterns within the Heterarthrinae exhibit striking similarities to patterns found in co-occurring herbivore taxa.     

Sawfly taxa (Hymenoptera,Symphyta) described by Edward Newman and Charles Healy

Type specimens of seven nominal species of sawfly described by Edward Newman and one by Charles Healy were studied. This material is housed in the Oxford University Museum of Natural History, United Kingdom. The following new synonymies are proposed (valid names in parentheses): Hartigia Schiødte, 1839 (Phylloecus Newman, 1838), Cephus helleri Taschenberg, 1871 (Phylloecus faunus Newman, 1838) and Euura gallae Newman, 1837 (Euura mucronata (Hartig, 1837)). The type species of Euura Newman, 1837 and Euura subgenus Gemmura E. L. Smith, 1968 belong to the same taxonomic species, Euura mucronata (Hartig, 1837), so that these genus group names become new synonyms. Lectotypes are designated for Phyllotoma tormentillae Healy, 1868, Fenusa ianthe Newman, 1837, Fenusa parviceps Newman, 1837, Selandria pallida Newman, 1837 and Phylloecus faunus Newman, 1838. 26 new combinations are proposed for species formerly placed in Hartigia and here transferred to Phylloecus, and 4 original combinations are re-instated as valid.     

Larval habits, host-plant associations, and speciation in nematine sawflies (Hymenoptera: Tenthredinidae)

Adaptive radiations consist of two intertwined processes, diversification of species and diversification of their ecological niches, but it is unclear whether there is a causal link between the processes. In phytophagous insects, ecological diversification mainly involves shifts in host-plant associations and in larval feeding habits (internal or external) on different plant parts, and several observations indicate that speciation is facilitated by host shifts. Data on host use in individual species suggest that internal feeders are less likely to colonize new hosts than external-feeding taxa and, consequently, increases in collective host ranges and species numbers should be slowed down in endophagous lineages. We tested these related hypotheses by using phylogenetic information to reconstruct the evolutionary history of larval resource use in the sawfly subfamily Nematinae, a group of 1000 plus species with a broad range of niches: the subfamily's combined host range includes over 20 plant families, and larvae may feed externally on leaves or needles, or internally, for example, in buds, fruits, leaves, or galls. The results show that: (1) Most internally feeding groups have evolved independently from external-feeding ancestors, but several distinct internal habits have appeared convergently multiple times; (2) Shifts among host taxa are clearly more common than changes in larval habits; (3) The majority of host switches have occurred among phylogenetically close plant groups, but many shifts are manifest among distantly related, ecologically proximate hosts; (4) Although external feeding characteristic of the common ancestor of Nematinae is associated with relatively high rates of host-shifting, internal feeders are very conservative in their host use; (5) In contrast, the effect of endophagy on speciation probabilities is more variable: net speciation rates are lowered in most internal-feeding groups, but a striking exception is found in species that induce galls on Salicaceae. The loose connection between collective host ranges and species diversity provides empirical support for theoretical models suggesting that speciation rates are a function of a complex interplay between "intrinsic" niche width and resource heterogeneity.     

Egg Deposition Behavior in the Haplodiploid Sawfly Athalia rosae ruficornis Jakovlev (Hymenoptera: Symphyta: Tenthredinidae)

The egg deposition behavior of the turnip sawfly, Athalia rosae (Hymenoptera: Symphyta), is described. Both unmated and mated females lay eggs individually inside of fresh young leaves of cruciferous plants. During an oviposition event, females exhibit a distinct pause in abdominal contractions just before the actual egg deposition act. Unmated females show a longer pause (11.31 s on average) than mated females (4.38 s on overall average). By employing an eye color mutation, the sex of the eggs laid by females was ascertained. Females mated once lay mostly fertilized (diploid female) eggs initially but begin to lay a considerable number of unfertilized (haploid male) eggs later in life. The laying of an unfertilized egg is associated with a longer pause (6.98 s on average) than the laying of a fertilized egg (3.76 s on average). These results are in contrast to previous reports on apocritan Hymenoptera, where the presence of a pause or a longer pause during oviposition was associated with the deposition of fertilized eggs rather than unfertilized eggs. The possibility that mated Athalia rosae females control fertilization and its implications for sex allocation strategies are discussed.     

Phylogenetic analyses elucidate the inter‐relationships of Pamphilioidea (Hymenoptera,Symphyta)

The phylogeny of the superfamily Pamphilioidea is reconstructed using morphology and DNA sequence data of living and fossil taxa by employing two phylogenetic methods (maximum parsimony and Bayesian inference). Based on our results, the monophyly of Pamphilioidea and Pamphiliidae are corroborated, whereas two extinct families, Xyelydidae and Praesiricidae, are not monophyletic. Because members of Praesiricidae together with Megalodontes form a monophyletic group, we propose that the paraphyletic Praesiricidae is synonymized under Megalodontesidae (syn. nov.). The origin of Pamphilioidea is hypothesized to be as early as the Early Jurassic. To better understand morphological evolution in the early lineages of Pamphilioidea, ancestral states of the first flagellomere and the first and second abdominal terga are reconstructed on the morphology‐based tree. In addition, three new genera (Medilyda, Brevilyda, Strenolyda) with five new species (Medilyda procera, M. distorta, Brevilyda provecta, Strenolyda marginalis and S. retrorsa) are described based on well‐preserved xyelydid fossils from the Middle Jurassic Jiulongshan Formation of north‐eastern China.     

The position of the Hymenoptera within the Holometabola as inferred from the mitochondrial genome of Perga condei (Hymenoptera: Symphyta: Pergidae)

We sequenced most of the mitochondrial genome of the sawfly Perga condei (Insecta: Hymenoptera: Symphyta: Pergidae) and tested different models of phylogenetic reconstruction in order to resolve the position of the Hymenoptera within the Holometabola, using mitochondrial genomes. The mitochondrial genome sequenced for P. condei had less compositional bias and slower rates of molecular evolution than the honeybee, as well as a less rearranged genome organization. Phylogenetic analyses showed that, when using mitochondrial genomes, both adequate taxon sampling and more realistic models of analysis are necessary to resolve relationships among insect orders. Both parsimony and Bayesian analyses performed better when nucleotide instead of amino acid sequences were used. In particular, this study supports the placement of the Hymenoptera as sister group to the Mecopterida.     

Mitonuclear discordance is caused by rampant mitochondrial introgression in Neodiprion (Hymenoptera: Diprionidae) sawflies

We investigate the pervasiveness of hybridization and mitochondrial introgression in Neodiprion Rohwer (Hymenoptera; Diprionidae), a Holarctic genus of conifer-feeding sawflies. A phylogenetic analysis of the lecontei species group revealed extensive discordance between a contiguous mitochondrial region spanning three genes (COI, tRNA-leucine, and COII) and three nuclear loci (EF1alpha, CAD, and an anonymous nuclear locus). Bayesian tests of monophyly and Shimodaira-Hasegawa (SH) tests of topological congruence were consistent with mitochondrial introgression; however, these patterns could also be explained by lineage sorting (i.e., deep coalescence). Therefore, to explicitly test the mitochondrial introgression hypothesis, we used a novel application of coalescent-based isolation with migration (IM) models to measure interspecific gene flow at each locus. In support of our hypothesis, mitochondrial gene flow was consistently higher than nuclear gene flow across 120 pairwise species comparisons (P < 1 x 10(-12)). We combine phylogenetic and coalescent evidence to identify likely cases of recent and ancient introgression in Neodiprion, and based on these observations, we hypothesize that shared hosts and/or pheromones facilitate hybridization, whereas disparate abundances between hybridizing species promote mitochondrial introgression. Our results carry implications for phylogenetic analysis, and we advocate the separation of high and low gene flow regions to inform analyses of hybridization and speciational history, respectively.