Sawfly Larvae Research Articles

Leaf herbivory causes abortion of selfed seeds in Rhododendron kaempferi var. kaempferi

AbstractPlant reproduction is often inhibited by herbivorous leaf damage, which affects the resource pool allocated for reproduction. Rhododendron kaempferi var. kaempferi is a semi‐evergreen shrub widely distributed in Japan, and its leaves are occasionally damaged by sawfly larvae (Arge similis). This species is partially self‐compatible, but its selfed seedlings suffer from inbreeding depression. Our study aimed to clarify (1) the magnitude of herbivorous damage under natural conditions, (2) the effects of foliage damage on seed number and mass, and (3) the possibility of selective abortion of selfed seeds to maintain outcrossed seed production under resource limitation. In the 2022 survey, 2 of the 20 ramets observed were collectively parasitized by sawfly larvae, and the most damaged ramet had a 59.6% foliage loss. In contrast, the herbivorous damage in 2023 was consistently low throughout the growing season, averaging a 3.2% loss. Leaf excision reduced the seed number per fruit (i.e., low seed‐set rate) but did not affect the individual seed mass. The outcrossing rate of the excision treatment (81.7%) was significantly higher than that of the control (72.0%). The values of seed‐set rate × outcrossing rate were 0.172 for the excision treatment and 0.171 for the control, nearly equal. Our results indicated that (1) sawfly larvae damage was concentrated on a few specific plants, (2) intense foliage damage reduced seed number but not seed mass, and (3) R. kaempferi mitigated the decline in outcrossed seed production by the abortion of selfed seeds when leaves were intensively damaged.

Spatiotemporal and Trade-Off Dynamics in Prey–Predator Model with Domed Functional Response and Fear Effect

In the ecological scenario, predators often risk their lives pursuing dangerous prey, potentially reducing their chances of survival due to injuries. Prey, on the other hand, try to strike a balance between reproduction rates and safety. In our study, we introduce a two-dimensional prey–predator model inspired by Tostowaryk’s work, specifically focusing on the domed-shaped functional response observed in interactions between pentatomid predators and neo-diprionid sawfly larvae. To account for the varying effectiveness of larval group defense, we incorporate a new component into the response equation. Our investigation delves into predator trade-off dynamics by adjusting the predator’s mortality rate to reflect losses incurred during encounters with dangerous prey and prey’s trade-off between safety and reproduction rate incorporating this domed-shaped functional response. Our model demonstrates bistability and undergoes various bifurcations, including transcritical, saddle-node, Hopf, Bogdanov–Takens, and Homoclinic bifurcations. Critical parameters impact both predator and prey populations, potentially leading to predator extinction if losses due to dangerous prey encounters become excessive, highlighting the risks predators face for their survival. Furthermore, the efficacy of group defense mechanisms can further endanger predators. Expanding our analysis to a spatially extended model under different perturbations, we explore Turing instability to explain the relationship between diffusion and encounter parameters through both stationary and dynamic pattern formation. Sensitivity to initial conditions uncovers spatiotemporal chaos. These findings provide valuable insights into comprehending the intricate dynamics of prey–predator interactions within ecological systems.

Assessing the Efficacy of Metarhizium anisopliae (Metschnikoff) Sorokin as a Biological Control Agent against Rose Sawfly Larvae

Increasing concerns over the environmental impact of chemical pesticides have prompted the exploration of alternative, and eco-friendly solutions for controlling insect pests. The use of entomopathogenic fungus (EPF) as a biological control agent is of paramount importance. We aimed to investigate the effect of different concentrations of Metarhizium anisopliae (Metschnikoff) Sorokin on larval mortality and pupal formation, of sawfly larvae, a major pest of rose plants. Our study revealed a concentration-dependent effect of M. anisopliae on sawfly larvae. At 7 days after EPF exposure, the highest concentration (1 × 109 conidia/ml) led to a mortality rate of 65.0% and at the 11th day, the larval mortality was reached up to 82.5%. The highest EPF concentration resulted in a minimal pupal formation (7.5%). This study demonstrates the potential of M. anisopliae as a valuable biological control agent against sawfly larvae infestations in rose plants.

Scientific Note: Caterpillar mimicry across orders: Pine sawfly larvae as a possible model for an Erythrina Leafroller caterpillar, Agathodes monstralis (Lepidoptera, Crambidae)

Scientific Note: Caterpillar mimicry across orders: Pine sawfly larvae as a possible model for an Erythrina Leafroller caterpillar, Agathodes monstralis (Lepidoptera, Crambidae)

Nearctic “Slug” Sawfly Larvae of the Genus Caliroa Costa (Hymenoptera: Tenthredinidae): New Rearing Records and a Summary of Hosts, Descriptions, and Distribution Records

Hosts, larval descriptions, biology, and distribution records are reviewed for the 16 described Nearctic species of Caliroa Costa (Tenthredinidae). We report the first rearing records for C. lunata MacGillivray, which feeds on Staphylea trifolia L. (Staphyleaceae). Caliroa obsoleta (Norton), previously known from Quercus L. spp. (Fagaceae), has now been reared from Populus tremuloides Michx. (Salicaceae). The larva of another Quercus feeder, C. petiolata Smith, is described and illustrated for the first time. A key is provided to both known and unidentified larvae, drawing from the literature and new observations, including an extensive review of online photographs.

Nueva especie de mosca sierra del género ZadiprionRohwer (Hymenoptera: Diprionidae) atacando Pinus cembroides (Zucc.) en Tamaulipas, México

Introduction:Zadiprion Rohwer is a genus of sawflies including seven species that cause defoliations in coniferous forests. Objective: To determine the species of Zadiprion sawflies infesting Pinus cembroides (Zucc.) in Miquihuana, Tamaulipas. Materials and methods: Biological material was collected from sawfly larvae. Part of the material was preserved in 70 % alcohol for morphological description, another in 96 % anhydrous alcohol for molecular identification and another portion was placed in a Binder 720 KBW E5.1 to complete the biological cycle and obtain adults. The ovipositor of the female and phenology during five years were described. Results and discussion: The sawfly larva has an orange-brown head with a small circular eyestalk, a longitudinal brown spot on the dorsum, two white lines on the sides and a dark subdorsal stripe. The female is light yellow with dark sutures on the thorax. The lancet of the ovipositor has nine rings; the first is inverted “U” shaped. Males are mainly black with yellowish legs and a yellowish-brown spot in the postocellar area; there is no yellowish-brown pronotum or tegula and the harpes are rounded and pale at the apex. The population is different from Z. rohweri (Middleton) and Z. jeffreyi (Smith), reported in GenBank; however, they are related. Conclusions: The sawf ly under study is a new species and was recorded as Zadiprion borjaisp. nov. (GenBank: ON181557).

First record of Azalea Sawfly (<i>Euura lipovskyi</i>, Hymenoptera: Tenthredinidae) in Canada

Azalea Sawfly (Euura lipovskyi) larvae found feeding on foliage and flowers of cultivated Flame Azalea (Rhododendron calendulaceum) in Ottawa, Ontario, in late May 2021 are the first records of this sawfly in Canada. The native range of Azalea Sawfly includes the eastern United States, but the species has extended its distribution recently to the Pacific northwest of North America and Europe. Recorded foodplants include Rhododendron calendulaceum, Rhododendron luteum, Rhododendron obtrusum, Rhododendron occidentale, Rhododendron molle, Rhododendron viscosum, and possibly Early Azalea (Rhododendron prinophyllum), all in Rhododendron section Pentanthera. The new combinations Euura lipovskyi and Euura azaleae are proposed.

Integrated taxonomy unveils new species of Trigonalyidae (Insecta, Hymenoptera) from Yunnan, China

Trigonalyidae are rarely collected hyperparasitoids that attack the larvae of Ichneumonoidea, and Tachinidae associated with phytophagous sawfly or Lepidopteran larvae, or primary endoparasitoids of Vespidae larvae. Trigonalyidae mainly occur in tropical and subtropical regions, but recent studies indicate that they are found to be fairly common in mountainous regions. In this study, DNA barcoding methods based on sequences of the COI gene were used to discriminate Trigonalyidae species from Yunnan Province, which is situated in a mountaineous area of southwest China. In total, 25 COI sequences belonging to 14 morphospecies of four genera were obtained. The intraspecific pairwise distances ranged from 0 to 3.3% and the interspecific pairwise distances ranged from 5.3% to 17.3%. The delimitations of all studied species are congruent with the morphological identification results in both ABGD and bPTP methods. Based on both morphological and molecular analyses, four species from Yunnan are described as new: Jezonogonalos eburnalva Zhang & Chen, sp. nov., Lycogaster umbonata Chen & van Achterberg, sp. nov., Taeniogonalos albidorsalis Zhang & Chen, sp. nov., and T. paradoxica Zhang & Chen, sp. nov.

HYPERPARASITISM IN A JEFFREY PINE (PINUS JEFFREYI) DEFOLIATOR IN THE SIERRA SAN PEDRO MÁRTIR NATIONAL PARK, BAJA CALIFORNIA, MEXICO

Sawfly larvae of the family Diprionidae are defoliators of conifers, undergoing cyclical outbreaks. Here, we present a tachinid fly, identified as a Chetogena species, which was found parasitizing diprionid larvae from a recent outbreak on Jeffrey pines (Pinus jeffreyi) in Baja California's Sierra San Pedro Mártir National Park. The findings reported here are a new distributional record for Chetogena in Baja California.

Estimation of Stem-Solidness and Yield Components in Selected Spring Wheat Genotypes

Solid-stemmed wheat genotypes are better protected from damage caused by wheat stem sawfly (Cephus pygmaeus L.) larvae and at lower risk of lodging, as they are additionally strengthened. The aim of the study was to analyse the stem-solidness of fifty spring wheat cultivars with pith. A field experiment was conducted at the Agricultural Research Station Dłoń, Poland in the years 2012–2014. The method recommended by the International Union for the Protection of New Varieties of Plants (UPOV) and the methodology described by DePauw and Read were used to analyse the stem-solidness. The statistical analysis of the results showed that the stems of the wheat cultivars differed in their, therefore, they were divided into seven classes. There were nine Polish cultivars, two genotypes from Canada (BW 597 and AC Elsa) and one Portuguese genotype (I 836) with hollow stems. There were only nine solid-stemmed cultivars. Both methodologies were used to assess the filling of the stem in the whole plant upon analysis of its filling at the cross-section of the first internode. Both methods gave the same results. The DePauw and Read methodology showed that the internodes in the lower part of the plants were filled to the greatest extent. The same genotypes collected in the consecutive years of the study differed in the filling of their stems with pith. These differences were influenced by the environmental conditions.

Behavior and body size modulate the defense of toxin-containing sawfly larvae against ants

The sawfly larvae of most Argidae and Pergidae (Hymenoptera: Symphyta) species contain toxic peptides, and these along with other traits contribute to their defense. However, the effectiveness of their defense strategy, especially against ants, remains poorly quantified. Here, five Arge species, A. berberidis, A. nigripes, A. ochropus, A. pagana, A. pullata, plus three Pergidae species, Lophyrotoma analis, Lophyrotoma zonalis, Philomastix macleaii, were tested in laboratory bioassays on ant workers mainly of Myrmica rubra. The experiments focused on short-term predator–prey interactions, sawfly survival rate after long-term interactions, and feeding deterrence of the sawfly hemolymph. The larvae of Arge species were generally surrounded by few ants, which rarely bit them, whereas larvae of Pergidae, especially P. macleaii, had more ants around with more biting. A detailed behavioral analysis of Arge-ant interactions revealed that larval body size and abdomen raising behavior were two determinants of ant responses. Another determinant may be the emission of a volatile secretion by non-eversible ventro-abdominal glands. The crude hemolymph of all tested species, the five Arge species and L. zonalis, was a strong feeding deterrent and remained active at a ten-fold dilution. Furthermore, the study revealed that the taxon-specific behavior of ants, sting or spray, impacted the survival of A. pagana but not the large body-sized A. pullata. The overall results suggest that the ability of Arge and Pergidae larvae to defend against ants is influenced by the body size and behavior of the larvae, as well as by chemicals.

Plant Mediated Interactions: Lower Sawfly Survival on Pines Previously Browsed by Moose

Insect herbivore performance and arthropod communities can be affected by mammalian grazing and browsing via altered plant communities and vegetation structure. Far less is known about whether changes to plant architecture can cause similar effects. Browsing generated changes to within plant architecture could potentially have large consequences for arthropod communities, herbivore survival and eventually damage to plants. This study investigates plant-mediated effects of ungulate browsing on arthropod predator communities and on the survival of herbivorous insects. More specifically we studied how different levels of ungulate browsing (1) influenced the arthropod predator community on Scots pine (Pinus sylvestris) and (2) affected the survival of the European pine sawfly (Neodiprion sertifer). We related these response variables to browsing-inflicted changes in pine architecture. An observational study of generalist arthropod predators on pine trees revealed a trend toward a quadratic response of ants to browsing intensity—i.e., a higher abundance of ants on moderately browsed trees and lower abundance on intensively browsed trees. A field survey of sawfly larvae revealed a 19% lower larval survival on browsed compared to un-browsed pines, but no difference in survival comparing pines with moderate and high intensity of browsing. A structural equation model revealed that moose generated changes to pine architecture had only a small effect on sawfly larval survival, suggesting additional mediating pine traits affected by browsing. We conclude that insect survival can be altered by ungulate browsing, which could affect damage levels.

Comparative anatomy of the larvae of argid sawflies (Hymenoptera: Argidae): a phylogenetic approach

The larval stage remains unknown for many sawflies, making it difficult to explore the phylogenetic significance of larval morphology. Here, we assemble a data set from the larval anatomy of 22 genera of Argidae and Zenargidae. We scored 85 characters for 48 terminal taxa and use a maximum parsimony approach applying equal (EW) and implied weights (IW) for phylogenetic reconstruction. We describe in detail for the first time the final larval instar of Zenarge turneri to illustrate the character systems employed. We retrieve the topology Zenarge + (Argidae s. stricto + Pergidae) in both EW and IW analyses; however, the branch support is low. We explore the phylogenetic relationships and character optimization based on the k value = 15 IW tree. Argidae s. stricto and Pergidae are recovered only under IW analyses. Within Argidae, two main clades are retrieved; these are congruent with the subfamilies Arginae and Sterictiphorinae s. Benson (1963). The genera Arge and Didymia are not retrieved as monophyletic. In general, the relationships produced by analyzing the larval morphology are consistent with those derived from adult morphology. We identify some patterns in the evolution of larval morphology of the Argidae.

Some sawfly larvae survive predator-prey interactions with pentatomid Picromerus bidens.

Most Asopinae stinkbugs (Hemiptera: Pentatomidae) prey on other insects, including sawfly larvae (Hymenoptera: Symphyta). Sawfly larvae of the Argidae and Pergidae contain toxic peptides, but whether they are defended against stinkbugs remains poorly studied. A literature survey indicates that no publication is devoted to laboratory tests specifically using these sawflies against stinkbugs. Here, laboratory bioassays were made with the stinkbug Picromerus bidens and four sawfly species at last larval instars: Arge ochropus (Argidae), Arge pagana (also tested at medium instars), Lophyrotoma zonalis (Pergidae), and Allantus rufocinctus (Tenthredinidae). Following 24 h of possible predator-prey interactions, no larvae of A. rufocinctus survived, whereas most or all larvae of the other sawfly species did survive and were still alive 48 h later. When feeding on an argid or pergid larva, the feeding periods lasted on average 6-20 s only, some bugs removing their rostrum and abruptly backing away. Full-grown larvae of A. pagana were attacked less than younger ones. It is likely that the tested Argidae and Pergidae are well defended against P. bidens by potent, internal antifeedants, while defensive body movements combined with a large body size play a secondary role.

Assessing temporal dynamics of predation and effectiveness of caterpillar visual defense using sawfly larval color and resting posture as a model.

Caterpillars (Lepidoptera and Symphyta larvae) employ diverse visual defensive tactics, and effectiveness of such tactics may be highly dynamic across time due to seasonal changes in the predator assemblages and their preferences. However, this has rarely been studied especially in tropical regions. Here we assessed temporal changes in the defensive value of caterpillar color and shape, using six types of plasticine dummy caterpillars: three colors (green, black, and white) × two shapes (curled and straight). These dummy caterpillars were deployed five times over different seasons in tropical forests of Xishuangbanna (China) and, as a comparison, twice in a temperate forest of Hirosaki (Japan). The colors and shapes of dummy caterpillars simulate visual traits of black sawfly larvae which take the curled resting posture in tropical rainforests of Xishuangbanna, apparently masquerading excrements commonly found on plants, while in Hirosaki there is no black-curled sawfly larvae and few excrements on plants. We found no significant effects of caterpillar colors or shapes on predation in Hirosaki. In contrast, black and curled caterpillars received significantly lower predation by birds in Xishuangbanna constantly across time. However, we were unable to provide evidence that the black-curled sawfly larvae are masquerading as excrements. Shapes of the dummy caterpillars also affected the predation by ants and parasitoid wasps at certain times. This is the first report on ecological function of the curled posture of sawfly larvae, and we demonstrated the importance to assess the temporal dynamics of predation and effectiveness of defensive tactics in tropical forests.

Effect of forest stand type on host plant quality and direct and indirect effects on pine sawfly performance

Abstract Observed lower levels of herbivory in mixed compared with monoculture stands have been hypothesized to depend on top‐down forces, through higher predation pressure by natural enemies or through bottom‐up mechanisms through plant quality effects on herbivore performance. In this study, we compared the performance measured as host plant induced mortality, cocoon weight, and predation mortality of the European pine sawfly Neodiprion sertifer (Geoffroy) (Hymenoptera, Diprionidae) in mixed and monoculture forest stands. We did not observe a difference in host plant induced mortality, cocoon weight, or predation mortality between mixed and monoculture forest stands. We did find an effect of local conditions around each experimental tree on pine sawfly performance. For example, the nitrogen content of pine needles is negatively affected by the proportion of pine around the experimental tree, which in turn increases the survival of sawfly larvae. The results suggest that local conditions around individual trees are more important for the performance of the European pine sawfly than stand type, i.e. mixed or monoculture plant stands. We conclude that the ongoing trend for diversification within commercial forestry calls for more research where the effects of both bottom‐up and top‐down effects are studied at several spatial scales.

Morphogenesis of embryonic appendages of Arge pagana Panzer (Hymenoptera: Argidae)

The larvae of hymenopteran Symphyta are eruciform, with several pairs of abdominal prolegs in addition to three pairs of thoracic legs. However, it is still controversial whether these abdominal prolegs are serially homologous with the thoracic legs. Here we studied the embryonic development of the larval appendages of the large rose sawfly Arge pagana (Panzer, 1798) to investigate the origin and homologous relationship of the abdominal prolegs of Argidae. The results show that paired swellings (proleg primordia) on the embryonic abdomen are not aligned with the thoracic legs, but are slightly closer to the midventral line. During the embryonic development, the thoracic leg primordia are differentiated into six segments, while the abdominal appendage primordia remain unsegmented and eventually develop into conical prolegs. The abdominal prolegs of larval A. pagana are likely developed from the endites of the primary embryonic appendages, and the paired anal prolegs arise from the eleventh abdominal segment. Therefore, the abdominal prolegs of sawfly larvae are very likely to have an appendicular nature but not the main axes of appendages.

Entomopathogenic nematodes control Plum Sawflies (Hoplocampa minuta and H. flava)

AbstractPlum sawflies are among the most damaging pests of European plum. Current control strategy implies insecticide application. Three species of entomopathogenic nematodes (EPN), Steinernema feltiae Filipjev, S. carpocapsae Weiser and Heterorhabditis bacteriophora Poinar were tested under laboratory and field conditions to assess effectiveness against larval and adult stages. Laboratory tests resulted in up to 100% mortality of last instar larvae before construction of a cocoon. However, the nematodes were not able to penetrate the cocoon. Foliar application did not result in plum sawflies larvae infestation by EPNs. Under field conditions, the nematodes reduced the number of emerging adults by application against sawfly larvae in the previous year before migration into the soil for overwintering by 62%–92%. Application of the nematodes against adults just before their anticipated emergence resulted in reduction of fruit infestation up to 100%. Mean results of 5 trials using caged trees were 47.8% with S. feltiae, 56.3% with S. carpocapsae and 62.9% with H. bacteriophora. In open field trails, control of adults obtained with S. feltiae at 0.5 million nematodes/m2 was 98.2 and 67.8% and at 0.25 million m−2 41.7 and 41.2%. Forecasting adult emergence and optimal soil moisture conditions are essential for success of the nematode application.

Lagged effects of sawfly leaf herbivory on reproductive organs in cherry trees: Overcompensation in flower production reduces quality of fruits and seeds

Herbivores reduce plant productivity by removing part of the assimilation surface. Also, they can alter plant traits that affect plant–pollinator interactions and reproductive success. The objective of this study was to evaluate the impact of defoliation by sawfly (Caliroa cerasi) larvae on fruit production and quality in three cultivars of sweet cherry (Prunus avium). We hypothesized that the fruit production and quality is reduced as a consequence of changes in the allocation of resources within the plant in response to partial leaf removal during the previous year. Number of flowers per branch meter was higher in infested trees than in non-infested trees, while the number of fruits per branch meter was similar due to fruit abortion in all cultivars. Fruit quality was significantly affected by herbivory in different traits depending on cultivar. Infested Lapins and Van trees had significantly lower soluble solid content than non-infested trees. Titratable acidity was higher and ripening index was lower in infested Bing and Lapins trees than non-infested trees. Infested Van trees also exhibited a significant decrease in equatorial diameter and fresh fruit weight as well as pulp fresh weight and dry weight of seed compared to non-infested trees. Overall our study highlights that the direct impact of herbivores at leaf level has lagged effects on productivity in terms of fruit and seed quality in the year following the leaf damage.

Top-down pressure by generalist and specialist natural enemies in relation to habitat heterogeneity and resource availability

Habitat heterogeneity might promote the abundance and richness of natural enemies potentially leading to higher top-down pressure on herbivorous insects. Heterogeneous habitats could provide natural enemies with more abundant and alternative resources and a greater variety of micro-habitats. Natural enemies with different searching behaviours, e.g. generalists and specialists, could be affected in different ways by habitat heterogeneity, thus affecting their pressure on herbivorous insects.To understand how top-down pressure on herbivorous insects is promoted by habitat heterogeneity, it is crucial to investigate which parameters contributing to habitat heterogeneity affect not only the abundance and richness but also the searching behaviour of different natural enemies. We investigated the relationship between heterogeneity in forest habitats and the top-down pressure exerted by generalist predators and specialist parasitoids on larvae of the European pine sawfly (Neodiprion sertifer).We used forest stands with endemic or epidemic densities of resident sawfly populations. Within each stand we selected experimental trees to create variation in tree species diversity and density in their surrounding area, i.e. habitat heterogeneity. We found that a higher tree density increased the predation by generalists on sawfly larvae in stands with endemic sawfly densities. Parasitoids were less successful in stands with endemic sawfly densities. Total mortality depended on stand character and the proportion of pine around experimental trees.The explained variation in the response variables by the models is relatively low, indicating that other measures of heterogeneity, like understory vegetation and presence of dead wood could contribute to the observed variation. Also, interference between generalist and specialist enemies could affect the realized mortality pressure. Thus, the effect of tree species diversity in combination with these other measures of heterogeneity needs to be recognized to promote the presence and the activity of natural enemies in managed habitats.