Species Of Sawflies Research Articles

A new genus and species of Australian pergid sawfly (Hymenoptera: Symphyta, Pergidae) causing damage on grass (Poaceae)

Dalia graminis, new genus and species, is described from the Darwin area in the Northern Territory, Australia. The new species belongs to the subfamily Euryinae and is most closely related to the genera Clarissa and Diphamorphos. Dalia graminis sp. nov. is the first record of an Australian pergid sawfly feeding on grass (Poaceae) causing severe damage on economically important crops.

Defence effectiveness of easy bleeding sawfly larvae towards invertebrate and avian predators

Easy bleeding is a phenomenon discovered in some tenthredinid insects which possess a particularly low mechanical resistance of the integument, leading under mechanical stress to haemolymph exudation. It has a defensive effect against ants and wasps through harmful plant compounds which are sequestered in the haemolymph. Here we describe etho-ecological and some chemical aspects of the defence of easy bleeders and specify the range of predators to which easy bleeding might be effective. Beside a high haemolymph deterrence associated with low integument resistance across sawfly species, we also detected toxicity of the haemolymph of some species to workers of the ant Myrmica rubra. The behaviour of easy bleeders is to move slowly and, once disturbed, to become motionless, thereby probably impeding the tendency of a predator to attack. This behaviour had no beneficial effect for easy bleeders when attacked by the predatory bug Podisus maculiventris. Bugs could successfully and without harm prey on sawfly larvae without evoking easy bleeding. For the easy bleeder Athalia rosae, host plants with different secondary metabolite profiles, and, consequently, changes in haemolymph chemistry only slightly affected the feeding behaviour of the bugs. To test the effectiveness of easy bleeding towards a vertebrate predator, easy bleeders were offered to birds, Sturnus vulgaris. The body colouration of the sawfly larvae was of prime importance in determining the predator’s response when testing birds in a group. It is likely that easy bleeding is a defence strategy directed primarily towards foraging insects with biting-chewing mandibles and that it is much less active towards predatory insects with piercing-sucking mandibles as well as birds. The involvement of chemical and/or physical cues in the strategy is discussed with respect to these types of predators.

Structure and mechanical strength of larval cuticle of sawflies capable of “easy bleeding” a defence strategy against predators evolved in Tenthredinidae (Hymenoptera)

The cuticle of Tenthredinidae (Hymenoptera) larvae is ruptured after a very mild mechanical stress and hemolymph is released. This phenomenon, called “easy bleeding” is considered as a defence strategy against predators. We investigated the cuticle structure of some selected species capable of “easy bleeding” by light-, transmission- and scanning microscopy and compared it with phylogenetically-related sawfly species without this defense strategy (control). Cuticle thickness has no major influence on mechanical stability, but pronounced local differences in thickness seem to be inversely correlated with mechanical strength. The density of chitin fibrils is considerably reduced in animals capable of easy bleeding and the fibres form a loose 3D network in contrast to the densely packed layers seen in related “non easy bleeding” species like Strongylogaster multifasciata, where a pressure of 2584 kPa is needed to pierce the integument , and which served as a control. Efficient bleeders like Phymatocera aterrima (203 kPa) and Rhadinoceraea nodicornis (219 kPa) are devoid of any defined layers or other structural elements. In Athalia rosae (Allantinae) (539 kPa), and Aglaostigma discolor (Tenthredininae) (1494 kPa) – bleeders with medium efficiency – a reduced number of layers are observed by LM and TEM and a loose network of chitin fibres is visible after treatment with KOH.

Variable responses of folivorous sawflies to leaf quality of mountain birch

We studied whether the larval performance of four sawfly species feeding on mountain birch (Betula pubescens subsp. czerepanovii (Orlova) Hämet-Ahti) leaves at different times of the growing season was related to the same chemical and physical leaf traits. In the three phenologically earliest species, larval growth was related to the same set of leaf traits. In contrast, consumption of leaf material was related to different leaf traits in all of the four species. Leaf suitability for herbivore growth and tree resistance to herbivore consumption were thus not always determined by the same leaf traits. Leaf water content and toughness had the strongest associations with larval performance. Phenolics, which are often considered the main resistance compounds in deciduous trees, explained only a small part of the variance in leaf consumption, but some groups of phenolics were negatively related to larval growth. In conclusion, the same mountain birch trees were not resistant to all of the studied sawflies in terms of leaf consumption, but low leaf suitability, which was related to the same set of leaf traits in the case of three sawfly species, may serve birch resistance, e.g., by exposing larvae to natural enemies for a longer period.

Phylogeography of two parthenogenetic sawfly species (Hymenoptera: Tenthredinidae): relationship of population genetic differentiation to host plant distribution

This study compares the population genetic structure of two obligate parthenogenetic sawfly species, Aneugmenus padi (L.) Zhelochovtsev and Eurhadinoceraea ventralis (Panzer) Enslin (Hymenoptera: Tenthredinidae). Allozymes were used to detect genetic differences in larvae collected at different sites in six European countries. For A. padi, scoring six polymorphic enzymes revealed the existence of five dominant, widely distributed clones and several more with only very few individuals occurring locally. The clonal diversity and identity differed across collection sites, with up to at maximum eight clones coexisting at a single locality. In contrast, in E. ventralis, individuals from different localities were all monomorphic for at least six different enzymes and are therefore assumed to belong to the same clone. Differences in population genetic structure of these sawfly species can be related to the differing distributions of their host plants: the fern, Pteridium aquilinum, the host of A. padi, has been an invasive species for more than two hundred years. Spread of clones of A. padi is likely to have closely followed the complex invasive pattern of spread of the plant. Larvae of E. ventralis were collected from local, horticultural plantings of Clematis spp. of recent origin probably with gardeners having traded plants infested with the sawfly. (C) 2004 The Linnean Society of London.

Release of phylogenetic constraints through low resource heterogeneity: the case of gall‐inducing sawflies

Abstract. 1. A group of six unusual sawfly species, which do not conform to the phylogenetic constraints hypothesis as it has been applied to sawflies, was examined in natural populations. All species were in the genus Pontania (Hymenoptera: Tenthredinidae), which induce galls on leaves of willow species (Salicaceae). An understanding of these non‐conformist species was important as a test of the validity of the general hypothesis.2. The six species of sawfly, Pontania mandshurica, P. cf. arcticornis, P. aestiva, P. arcticornis, P. pacifica, and P. nr. pacifica, showed no oviposition preference for long, vigorous shoots, in contrast to 37 documented tenthredinid species that have demonstrated such a preference. Rather, the non‐conformist species attacked the shortest shoot length classes more frequently and larval establishment in galls was successful.3. The evident escape from the phylogenetic constraint, which commonly limits sawfly attack to the most vigorous shoots in a willow population, resulted from low apparent heterogeneity of the resources exploited by these Pontania species. At the time of female oviposition, shoots and leaves were too uniform to allow discrimination by females among shoot length classes, resulting in random, or near random attack of shoots.4. The unusual relative uniformity of resources to which sawflies were exposed resulted from several characteristics. (1) Females emerged early relative to shoot growth phenology, making discrimination among shoot length and vigour difficult or impossible. (2) Low heterogeneity in leaf length resulted in resource similarity independent of shoot length. (3) Abscission of leaves occurred after emergence of larvae from leaf galls so that differential abscission of leaves in relation to shoot length became irrelevant. (4) In some cases, low variance in shoot lengths was evident in old ramets lacking long, vigorous shoots. Probably as a result of low resource heterogeneity, larvae survived well across all shoot length classes, revealing no ovipositional preference and larval performance linkage related to the exploitation of the longest shoot length classes in a population of willows, as in the conformist species. Therefore, larval survival did not provide positive feedback on female preferential behaviour for long shoots, as in the conformist species studied.

The fauna of sawflies (Symphyta, Hymenoptera) in a forest of sessile oak and hornbeam with butcher’s-broom (Querco-Carpinetum serbicum aculeatetosum Jovanovic, 1951) on Mt. Avala

In a phytocenosis of sessile oak and hornbeam with butcher?s broom (Querco-Carpinetum serbicum aculeatetosum Jovanovic 1951) on the territory of Mt. Avala, 42 species of sawflies belonging to the families Argidae Pamphiliidae and Tenthredinidae have been registered. The 42 species that were found, as many as 19 (or 45.23%) are new for the entomofauna of Serbia and Montenegro. Of these 19 species, one belongs to a genus newly recorded on our territory (the genus Cephaleia). The dominant family is the family Tenthredinidae, to which 38 of the registered species belong. The family Tenthredinidae is also dominant in this community with respect to the number of specimens caught, as only a few specimens of species of the other two families were present. The subfamily Tenthredininae is the most numerous subfamily of the family Tenthredinidae inasmuch as 19 of its species were registered in the course of two-year sampling. The most abundant species in the observed phytocenosis are species of the genus Macrophya, while the majority of species of sawflies during the research were present in the field in only small numbers.

Surface structure, model and mechanism of an insect integument adapted to be damaged easily

BackgroundSeveral sawfly larvae of the Tenthredinidae (Hymenoptera) are called easy bleeders because their whole body integument, except the head capsule, disrupts very easily at a given spot, under a slight mechanical stress at this spot. The exuding haemolymph droplet acts as a feeding deterrent towards invertebrate predators. The present study aimed to describe the cuticle surface, to consider it from a mechanistic point of view, and to discuss potential consequences of the integument surface in the predator-prey relationships.ResultsThe integument surface of sawfly larvae was investigated by light microscopy (LM) and scanning electron microscopy (SEM) which revealed that the cuticle of easy bleeders was densely covered by what we call "spider-like" microstructures. Such microstructures were not detected in non-easy bleeders. A model by finite elements of the cuticle layer was developed to get an insight into the potential function of the microstructures during easy bleeding. Cuticle parameters (i.e., size of the microstructures and thickness of the epi-versus procuticle) were measured on integument sections and used in the model. A shear force applied on the modelled cuticle surface led to higher stress values when microstructures were present, as compared to a plan surface. Furthermore, by measuring the diameter of a water droplet deposited on sawfly larvae, the integument of several sawfly species was determined as hydrophobic (e.g., more than Teflon®), which was related to the sawfly larvae's ability to bleed easily.ConclusionEasy bleeders show spider-like microstructures on their cuticle surface. It is suggested that these microstructures may facilitate integument disruption as well as render the integument hydrophobic. This latter property would allow the exuding haemolymph to be maintained as a droplet at the integument surface.

Patterns of interspecific associations of stem gallers on willows

Abstract. The pattern of interspecific associations of three stem‐galling sawfly species (Euura atra,E. elaeagnos,E. purpureae) and three stem‐galling gallmidge species (Rabdophagasp. 3–5) was investigated on five willow taxa (Salix alba,S. fragilis,S. × rubens,S. elaeagnos,S. purpurea) at five natural sites in Central Europe. The willow species harboured specific species associations of two stem gallers, each pair consisting of oneEuuraand oneRabdophagaspecies. The stem gallers were patchily distributed and their densities varied significantly among willow host plant species, host plant individuals, and host plant sexes. Four of the six species showed a significant increase in galling rate with shoot length. The other two species were the sawfly and cecidomyiid pair that induce galls onS. purpurea. The preference of stem gallers to longer shoots was generally not related to higher larval performance in terms of survival. Only one species,Rabdophagasp. 5, was found to be more abundant on male plants. The correlation of densities of the species pairs of stem gallers was independent of willow sexes. Species pairs of stem gallers co‐occurring on the same willow species tended to attack different shoots within the same host plant individual. When species pairs co‐occurred on shoots they were usually found in similar densities as when occurring alone on shoots. The stem‐galling sawflies usually formed galls at the basal part of a shoot, whereas the gallmidgeR. sp. 5 (R. sp. 3 andR. sp. 4 showed no clear tendency) preferred the middle or distal part of a shoot. This is interpreted with differences of their phenology and oviposition period.

Simultaneous outbreaks of three species of larch web-spinning sawflies: influences of weather and stand structure

The first outbreaks of three species of larch web-spinning sawflies ( Cephalcia lariciphila japonica Shinohara, Cephalcia koebelei (Rohwer) and Acantholyda nipponica Yano and Sato (Hymenoptera: Pamphiliidae) that occurred in 1993 in non-native larch ( Larix leptolepis Gordon) plantations in Hokkaido, northern Japan, were examined in two distinct areas 500 km apart. We also examined annual changes in prepupal densities in the soil in seven larch stands chosen across a defoliated region in central Hokkaido. The influence of stand structure on sawfly density were examined in 30 larch stands. Defoliation by C. lariciphila, which took place in eastern Hokkaido, were restricted to a small area for 4 years, then increased rapidly from 1997 and reached 15,000 ha in 2000. Defoliation in central Hokkaido, which was caused by C. koebelei and A. nipponica, increased to 2600 ha in the next year after initiation of the outbreak, continued at this level for 4 years and diminished in 1999. In central and eastern Hokkaido, outbreaks were preceded by three consecutive years of high yearly average temperature, which occurred 2–4 years before the outbreaks. However, yearly precipitation did not change noticeably prior to the outbreaks. Annual changes in prepupal densities in central Hokkaido revealed that the density peaked earlier near the stands where the outbreak was first observed and peaked later in peripheral areas. This suggests that the outbreaks began in local epicenters and expanded to surrounding areas. Neither larch density (trees/area), tree size (height and diameter at breast height (DBH)) nor proportion of larch stems correlate with the prepupal densities although these factors varied considerably. Thus, after canopy closure, sawfly density does not seem to be influenced by the stand factors.

Synthesis and Lipase Catalyzed Stereoselective Acylation of Some 3‐Methylalkan‐2‐ols, Identified as Sex Pheromone Precursors in Females of Pine Sawfly Species.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Why does the larval integument of some sawfly species disrupt so easily? The harmful hemolymph hypothesis.

The larvae of several sawfly species belonging to the Tenthredinidae (Hymenoptera) have such a low mechanical resistance in the integument that slight mechanical damage to the integument is enough to provoke the release of hemolymph at a given spot. We quantified this phenomenon, which we call "easy bleeding", by measuring the pressure needed to pierce dissected sawfly integument. We also investigated the feeding deterrance of ethanolic extracts of the hemolymph by laboratory bioassays using Myrmica rubra ant workers. These traits, integument resistance and hemolymph deterrence, were inversely related, considering 22 tenthredinid species. A negative correlation was obtained by only taking into account the species of one tenthredinid tribe, namely the Phymatocerini (nine species studied). Our results support the "harmful hemolymph hypothesis" that we present here and that assumes a functional link between these morphological and chemical traits, jointly acting as a chemical defense strategy. We suspect hemolymph deterrence to be often due to sequestration of plant secondary metabolites. We discuss the role of easy bleeding, considering the fact that sawfly larvae are frequently the prey of invertebrate and vertebrate predators. It is suggested that invertebrates such as ants were more important than vertebrates in the evolution of easy bleeding.

Observations on the life history and habits of a tropical sawfly, Sericoceros mexicanus (Kirby), (Hymenoptera: Argidae) on Roatán Island, Honduras

Observations on the life history and habits of a tropical sawfly, Sericoceros mexicanus, on Roatán Island, Honduras, during January 2002, are reported. This sawfly occurs in southern Mexico and Central America where it feeds on the foliage of Coccoloba spp. On Roatán Island, the only host is seagrape, C. uvifera, a small to medium tree, which occurs on sandy beaches just above tide line. The adults are colourful insects and relatively strong fliers. They swarm around host trees on warm, sunny days and during cool or overcast periods, rest on seagrape foliage and branches. In 2002, a period of peak adult activity occurred between January 8 and10. Eggs are deposited in circular or slightly oval clusters on the undersides of seagrape leaves. Mean egg cluster size is 32.7, range 7–85. Female adults remain with the egg cluster until they die. Eggs hatch within two or three days of oviposition and the larvae feed gregariously on the edges of seagrape leaves, consuming all of the leaf tissue except the major veins. Larvae undergo six instars. However, the small number of instar VI larvae collected suggests that female larvae may undergo an extra instar, as is the case with other species of sawflies. Pupation occurs in parchment-like cocoons attached to leaves, leaf petioles and branches of seagrape. Occasionally, cocoons are attached to wooden surfaces such as picnic benches. A few instar VI larvae were seen with symptoms suggesting virus infection. While heavily infested trees can suffer complete defoliation, the insect appears to cause little or no permanent damage. Local residents regard the insect as a curiosity rather than a pest and report at least two periods of defoliation a year—January and August. Key words: Sericoceros mexicanus, seagrape, Coccoloba uvifera, sawflies, defoliation, tropical forest insects, forest insects

Community structure, survival and mortality factors in arctic populations of Eupontania leaf gallers

We studied survival, mortality factors, and community structure of nine species of leaf-galling sawflies, Eupontania spp., living on ten willow species (Salix spp.) at six sites on the Russian arctic tundra. The sawfly species represented two different gall types: the viminalis-type, which forms pea-shaped galls on the underside of leaf blades, and the vesicator-type, which forms bean-shaped galls on both sides of the leaf blade. Gall communities in the northernmost site had only one parasitoid species, but up to six parasitoids were found at the southernmost site. Inquiline parasitoids were encountered only in the two southern sites. Survival of the larvae varied between 20.0 and 82.8% among galler species at different sites. Parasitoids were the most important mortality factor for the sawflies. They caused mortality of 7.8-65.4%, depending on galler species and site, and it was highest in the northernmost site. Plant-specific mortality varied from 1.7 to 28.4% by galler species and it tended to decrease towards the north. Mortality from parasitoids was greater in the vesicator-type gallers than in the viminalis-type gallers. The total mortality caused by parasitoids in the arctic communities does not appear to differ from that in the diverse southern communities of Eupontania in Middle Europe, Scandinavia and North America, despite the assemblage having only a few members in the Arctic. The largest difference between the southern and the northern communities was the lack of inquiline parasitoids in the north. Our data do not support the hypothesis that abiotic, rather than biotic, factors would be more important in determining the abundance of populations of herbivorous insects in the harsh arctic environment.

Host specificity and host recognition in a chemically‐defended herbivore, the tenthredinid sawfly Rhadinoceraea nodicornis

AbstractThe sawfly Rhadinoceraea nodicornis Konow (Hymenoptera: Tenthredinidae) is a member of a closely related group of species, the tribe Phymatocerini, which feed on the Liliales and Ranunculales. It is known to sequester steroid alkaloids from its host plants, species in the genus Veratrum (Liliales: Melanthiaceae), and to use them as a defence against predators. There are known chemical relationships between the hosts of R. nodicornis and hosts of related sawfly species. We tested whether the R. nodicornis larvae would accept hosts of closely‐ and more distantly‐related sawflies, but found that they accepted only plant species in the genus Veratrum. This specificity was apparently innate, as it was independent of early larval experience. A feeding bioassay showed that the steroid alkaloids from Veratrum nigrum were phagostimulatory for R. nodicornis larvae, suggesting that they may be involved in host recognition. We discuss the possibility that the evolution of recognition of specific compounds may represent the mechanism of host radiation within the Phymatocerini.

The phenological window of opportunity for early‐season birch sawflies

Abstract 1. The phenological window of opportunity hypothesis posits that an insect herbivore cannot survive outside a specific leaf age interval of its host plant.2. Previous studies have shown that mountain birch displays extensive seasonal changes in leaf biochemical characteristics. Young, expanding leaves are full of water and amino acids but they also contain large amounts of protein‐precipitating gallotannins as well as flavonoid‐glycosides. Concentrations of these compounds decline during leaf growth whereas concentrations of sugars and proanthocyanidins and leaf toughness increase.3. Adult birch sawflies hatch in early summer and oviposit on growing leaves, which compels larvae to feed on leaves that are already well developed. The purpose of this study was to test whether leaves that were younger and biochemically different from the leaves available under natural conditions are within the phenological window of opportunity for the larvae of two early‐season birch sawfly species, Amauronematus amplus Konow and Pristiphora alpestris (Konow).4. Amauronematus amplus larvae survived better and developed faster, and P. alpestris larvae developed faster and became bigger, on atypically young leaves compared with larvae reared on leaves encountered normally. Therefore, these species can exploit the putative nutritional superiority of very young leaves, which probably outweighs the potential impact of the new set of secondary metabolites offered to them. In conclusion, young leaves that are consumed rarely by sawfly larvae are within their phenological window of opportunity, even though the timing of sawfly life cycles constrains their utilisation.

Comparison of the fat allocation patterns in female pine sawflies (Hymenoptera: Diprionidae)

The allocation of fat resources to somatic and reproductive tissues was studied in females of five species of pine sawflies (Diprion pini (L.), Diprion similis (Htg.), Gilpinia frutetorum (F.), Gilpinia pallida (Klug), Neodiprion sertifer (Geoffroy); Hymenoptera, Diprionidae). The soma and eggs of newly emerged females were separated and then put in ether to extract and determine their fat content. The fat allocation patterns differed between species. The gregarious outbreak species D. pini and N. sertifer allocated most of the fat to their eggs, whereas the gregarious non-outbreak species, G. pallida, allocated most to its somatic tissues. No modification of these basic allocation patterns was observed with increasing total fat content. In contrast, the solitary non-outbreak species, D. similis and G. frutetorum, invested equal amounts of fat in soma and eggs, and the proportion allocated to the egg load decreased as total fat content increased. That is, they invested additional resources in somatic tissues. Apparently, outbreak species tend to allocate more fat to reproductive tissues than non-outbreak species.

Synopsis of the Tenthredinidae (Hymenoptera) in Australia, including two newly recorded, introduced sawfly species associated with willows (Salix spp.)

AbstractTwo species of tenthredinid sawflies associated with willows are recorded from Australia for the first time: Pontania proxima (Lepeletier), which forms galls on Salix fragilis Linnaeus in Tasmania, and Amauronematus viduatus (Zetterstedt), which defoliates Salix babylonica Linnaeus in south‐eastern New South Wales. A key to the five introduced and three endemic species of Tenthredinidae known from Australia is provided. Notes on biology and distribution are given for all species.

Syntheses of female sex pheromone precursors of pine sawfly species and of some structurally related methyl-branched long-chain 2-alkanols.

3,7-Dimethyl-2-undecanol, 3,7,9-trimethyl-2-tridecanol, and 3,7, 11-trimethyl-2-tridecanol were synthesized as racemic mixtures in moderate yields. The alcohols are known precursors of the female sex pheromones of the pine sawfly species Diprion nipponica, Macrodiprion nemoralis, and Microdiprion pallipes, respectively. Stereoisomeric mixtures of 3,8,12-trimethyl-2-tridecanol, erythro-(2R,3R, 11R/S)-3,11-dimethyl-2-tetradecanol, 3,5-dimethyl-2-tetradecanol, and 5,7-dimethyl-2-tetradecanol, structurally related to sex pheromone alcohol precursors of pine sawfly species, were also synthesized in moderate yields. The key reaction in the syntheses was the ring opening of gamma-butyrolactones by using different alkyl lithiums as nucleophiles.

Seasonally varying diet quality and the quantitative genetics of development time and body size in birch feeding insects.

Genetic variance-covariance structures (G), describing genetic constraints on microevolutionary changes of populations, have a central role in the current theories of life-history evolution. However, the evolution of Gs in natural environments has been poorly documented. Resource quality and quantity for many animals and plants vary seasonally, which may shape genetic architectures of their life histories. In the mountain birch-insect herbivore community, leaf quality of birch for insect herbivores declines profoundly during both leaf growth and senescence, but remains stable during midsummer. Using six sawfly species specialized on the mountain birch foliage, we tested the ways in which the seasonal variation in foliage quality of birch is related to the genetic architectures of larval development time and body size. In the species consuming mature birch leaves of stable quality, that is, without diet-imposed time constraints for development time, long development led to high body mass. This was revealed by the strongly positive phenotypic and genetic correlations between the traits. In the species consuming growing or senescing leaves, on the other hand, the rapidly deteriorating leaf quality prevented the larvae from gaining high body mass after long development. In these species, the phenotypic and genetic correlations between development time and final mass were negative or zero. In the early-summer species with strong selection for rapid development, genetic variation in development time was low. These results show that the intuitively obvious positive genetic relationship between development time and final body mass is a probable outcome only when the constraints for long development are relaxed. Our study provides the first example of a modification in guild-wide patterns in the genetic architectures brought about by seasonal variation in resource quality.