Polymorphism of axillary bud galls induced by Rhopalomyia longitubifex (Diptera: Cecidomyiidae) on Artemisia princeps and A. montana (Asteraceae) in Japan and Korea, with designation of new synonyms

In the past, Rhopalomyia longitubifex, Rhopalomyia shinjii, and Rhopalomyia sp. (Diptera: Cecidomyiidae) have been regarded as independent species based on differences in the sizes and shapes of axillary bud galls induced on Artemisia montana (Asteraceae) in Japan and A. princeps in Japan and Korea. However, comparison of morphological features and molecular sequencing data indicate that these Rhopalomyia gall midges are identical and that the differences in gall shape are polymorphisms, although the measurements of gall height and diameter overlap slightly. This finding suggests that although galls have frequently been regarded as extensions of the phenotype of a species, differences in gall shape may not always be reliable for identifying gall‐inducing cecidomyiids. The older name, R. longitubifex, is applied to these gall midges, and the names that were applied to this species on later occasions are revised or synonymized. The mature and immature stages of R. longitubifex are redescribed and information on the distribution, host range, and gall size of this species is provided. We also discuss the role of gall polymorphism in the early stages of speciation.     

Stem‐galling moths provide cetoniine beetles with feeding sites via sap exudation of invasive alien plants

The alien moth Epiblema sugii (Lepidoptera: Tortricidae) induces stem galls on an invasive alien weed, Ambrosia trifida. During summer, along riverbanks in central Japan, the native insects Protaetia brevitarsis, P. orientalis submarumorea (Coleoptera: Scarabaeidae: Cetoniinae), and Camponotus vitiosus (Hymenoptera: Formicidae) feed on the sap exuded from the galls. The cetoniine beetles are highly aggregated among the galls and make wounds on the galls to facilitate sap exudation. Feeding on gall sap may be beneficial to the beetles due to the efficient intake of water and sugar, and the beetles’ inflicting wounds and feeding on the sap seem to have little effect on the gallers. This is a unique finding, where alien plant–galler interaction provides a feeding site for native insects.     

Phytohormones in Japanese Mugwort Gall Induction by a Gall-Inducing Gall Midge

A variety of insect species induce galls on host plants. Liquid chromatographic/tandem mass spectrometric analyses showed that a gall midge (Rhopalomyia yomogicola) that induces galls on Artemisia princeps contained high levels of indole-3-acetic acid and cytokinins. The gall midge larvae also synthesized indole-3-acetic acid from tryptophan. Close observation of gall tissue sections indicated that the larval chamber was surrounded by layers of cells having secondary cell walls with extensive lignin deposition, except for the part of the gall that constituted the feeding nutritive tissue which was composed of small cells negatively stained for lignin. The differences between these two types of tissue were confirmed by an expression analysis of the genes involved in the synthesis of the secondary cell wall. Phytohormones may have functioned in maintaining the feeding part of the gall as fresh nutritive tissue. Together with the results in our previous study, those presented here suggest the importance of phytohormones in gall induction.     

Nipponaphis species (Aphididae: Hormaphidinae) that form green galls on Distylium racemosum in Japan

Some species of the aphid genus Nipponaphis (Nipponaphidini) form green, globular or fig‐shaped galls on the evergreen Distylium racemosum, their primary host. Molecular phylogenetic analyses of aphid samples collected from both their galls and secondary hosts indicated the occurrence of four species in Japan: N. distychii, N. distyliicola, N. loochooensis and N. machilicola. The four species could also be discriminated from one another in morphology. The name N. litseae turned out to be a junior synonym of N. distychii. Galls formed by N. machilicola are reported for the first time in this paper. The life cycles of the four species are briefly reviewed.     

Host range of braconid species (Hymenoptera: Braconidae) that attack Asphondyliini (Diptera: Cecidomyiidae) in Japan

We reared six idiobiont braconids, Bracon asphondyliae, B. sunosei, B. tamabae, Simplicibracon curticaudis, Testudobracon longicaudis and T. pleuralis from 22 identified species and 11 unidentified segregates of Asphondyliini (Diptera: Cecidomyiidae) in Japan. A total of 22 cecidomyiid species and segregates were newly recorded as hosts of the braconids. Analysis of cytochrome oxidase subunit I (COI) did not show any evidence of host races among the braconids. Bracon sunosei, which was synonymized with B. asphondyliae, is restored to a valid species. The host range of the braconid species seemed to be related to the lineage of host genera within Asphondyliini.     

Evolutionary relationships of Pemphigus and allied genera (Hemiptera: Aphididae: Eriosomatinae) and their primary endosymbiont,Buchnera aphidicola

Aphids harbor primary endosymbionts, Buchnera aphidicola, in specialized cells within their body cavities. Aphids and Buchnera have strict mutualistic relationships in nutrition exchange. This ancient association has received much attention from researchers who are interested in endosymbiotic evolution. Previous studies have found parallel phylogenetic relationships between non‐galling aphids and Buchnera at lower taxonomic levels (genus, species). To understand whether relatively isolated habitats such as galls have effect on the parallel relationships between aphids and Buchnera, the present paper investigated the phylogenetic relationships of gall aphids from Pemphigus and allied genera, which induce pseudo‐galls or galls on Populus spp. (poplar) and Buchnera. The molecular phylogenies inferred from three aphid genes (COI, COII and EF‐1α) and two Buchnera genes (gnd, 16S rRNA gene) indicated significant congruence between aphids and Buchnera at generic as well as interspecific levels. Interestingly, both aphid and Buchnera phylogenies supported three main clades corresponding to the galling locations of aphids, namely leaf, the joint of leaf blade and petiole, and branch of the host plant. The results suggest phylogenetic conservatism of gall characters, which indicates gall characters are more strongly affected by aphid phylogeny, rather than host plants.     

Life history strategy and adult and larval behavior of Macrodiplosis selenis (Diptera: Cecidomyiidae), a species that induces leaf‐margin fold galls on deciduous Quercus (Fagaceae)

Life historical, behavioral and ecological traits of Macrodiplosis selenis, which induces leaf‐margin fold galls on Quercus serrata, Q. mongolica and Q. dentata (Fagaceae) in Japan and South Korea, were studied. Daily activity and larval development indicate that M. selenis is a diurnal and univoltine gall midge. In April, females lay their eggs both on upper and under surfaces of fresh leaves. The duration of the egg stage varies from 5 to 9 days, depending on daily temperatures. Hatched larvae crawl to the upper surface of the leaf margin, where they start to induce galls. Larvae become full‐grown in October, drop to the ground in November and overwinter in cocoons on the ground, while larvae of congeners mature in May and drop to the ground in June. A relatively long period of the second larval stadium from July to October on the host trees seems to be effective for M. selenis in avoiding summer mortalities caused by predation and aridity on the ground and by ectoparasitoids that attack mature larvae or pupae on the host leaves. The spatial distribution pattern of M. selenis leaf galls is contagious and the mean gall density per leaf is significantly correlated with the mean crowding. This study adds new insights of life history strategy and adult and larval behavioral pattern to the ecological knowledge of gall midges, and these kinds of information are essential for further studies of M. selenis population dynamics and interactions with other Quercus‐associated herbivores.     

Finding of Torymus koreanus (Hymenoptera: Torymidae) attacking Dryocosmus kuriphilus (Hymenoptera: Cynipidae) in Japan

Torymus koreanus (Hymenoptera: Torymidae) was reared from galls of Dryocosmus kuriphilus (Hymenoptera: Cynipidae) for the first time in Japan. We here report morphological features and partial mtDNA sequencing data of T. koreanus. Torymus koreanus has several common characteristics with species of the cyaneus group defined by Zavada (2003 ). According to the key to species groups defined by Graham and Gijswijt (1998 ), it does not belong to any species group because of the entire posterior margin of metasomal tergum five.     

Detection of an invasive gall-inducing pest, Quadrastichus erythrinae (Hymenoptera: Eulophidae), causing damage to Erythrina variegata L. (Fabaceae) in Okinawa Prefecture, Japan

In 2005, Quadrastichus erythrinae Kim, 2004 (Hymenoptera: Eulophidae), which induces stem, petiole, and leaf galls on Erythrina variegata L. (Fabaceae), was found on the following six islands in Okinawa Prefecture, Japan: Okinawa, Kume, Miyako, Ishigaki, Iriomote, and Hateruma. Galls were also found in Vietnam. In Japan, no further infestation records have been reported from any of Japan's other south‐western prefectures where Erythrina species grow. Because no Erythrina galls were observed in Okinawa Prefecture before 2005, Q. erythrinae seems to have invaded quite recently.     

First record of Adelges (Cholodkovskya) viridanus (Hemiptera: Adelgidae) in North America,with a description of the fundatrix form in Japan

Adelges (Cholodkovskya) viridanus (Cholodkovsky 1896) (Hemiptera: Adelgidae) is found throughout Eurasia where it is understood to be anholocyclic, feeding on species of larch (Larix), without host alternation. For the first time, we report this species in North America, outside of its native range, from specimens collected in an arboretum in Ohio, USA. Molecular phylogenetic analysis was inconclusive as to whether it was introduced from Europe or Asia. In addition, specimens collected from Picea jezoensis in Japan were confirmed for the first time as A. (C.) viridanus by matching DNA sequences to specimens collected on Larix. Therefore, A. (C.) viridanus is either capable of completing a host-alternating holocycle in Japan, or includes very recently diverged anholocyclic populations on Picea. Finally, we describe the adult fundatrix form, which was previously unknown.     

Bottom-up effects shift top-down community structure of the parasitoid guild that attacks Asphondylia borrichiae (Diptera: Cecidomyiidae) on Borrichia frutescens (Asteraceae)

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Abundance of Gall Midges on Poulsenia armata (Moraceae): Importance of Host Plant Size and Light Environment in Tropical Rain Forests1

We studied the effects of contrasting light environments on the relationship between the host plant size of Poulsenia armata and the abundance of two gall midges in a tropical rain forest in Veracruz, Mexico. The number and density of two gall morphs (i.e., laminar and vein‐petiole galls) were positively correlated with plant size only in trees found in the forest but not in gaps. The availability of foliar area of P. armata trees was greater in forest gaps than in the forest. The foliar area was positively correlated with the abundance of laminar galls in trees in forest sites, but not with vein‐petiole galls. We concluded that the abundance of two morphs of gall midges on P. armata was associated with host plant size only in the forest trees. Larger plants had more galls than small plants, although this relationship was affected by local light environments.     

Influence of galls of Phanacis taraxaci on carbon partitioning within common dandelion, Taraxacum officinale

We examined how leaf galls, induced by the cynipid wasp Phanacis taraxaci, influence the partitioning of photoassimilates within the host, the common dandelion, Taraxacum officinale. Galled and ungalled plants were exposed to ¹⁴CO₂ and the labelled photoassimilates accumulating within galls and other parts of the host were measured. During the growth phase of the gall they were physiological sinks for photoassimilates, accumulating 9% to 70% of total carbon produced by the host, depending upon the number of galls per plant. High levels of ¹⁴C assimilation in the leaves of galled plants compared to controls, suggest that galls actively redirect carbon resources from unattacked leaves of their host plant. This represents a significant drain on the carbon resources of the host, which increases with the number and size of galls per plant. Active assimilation of ¹⁴C by the gall is greatest in the growth phase and is several orders of magnitude lower in the maturation phase. This finding is consistent with physiological and anatomical changes that occur during the two phases of gall development and represents a key developmental strategy by cynipids to ensure adequate food resources before larval growth begins.     

Phenotypic plasticity and similarity among gall morphotypes on a superhost,Baccharis reticularia (Asteraceae)

Understanding factors that modulate plant development is still a challenging task in plant biology. Although research has highlighted the role of abiotic and biotic factors in determining final plant structure, we know little of how these factors combine to produce specific developmental patterns. Here, we studied patterns of cell and tissue organisation in galled and non‐galled organs of Baccharis reticularia, a Neotropical shrub that hosts over ten species of galling insects. We employed qualitative and quantitative approaches to understand patterns of growth and differentiation in its four most abundant gall morphotypes. We compared two leaf galls induced by sap‐sucking Hemiptera and stem galls induced by a Lepidopteran and a Dipteran, Cecidomyiidae. The hypotheses tested were: (i) the more complex the galls, the more distinct they are from their non‐galled host; (ii) galls induced on less plastic host organs, e.g. stems, develop under more morphogenetic constraints and, therefore, should be more similar among themselves than galls induced on more plastic organs. We also evaluated the plant sex preference of gall‐inducing insects for oviposition. Simple galls were qualitative and quantitatively more similar to non‐galled organs than complex galls, thereby supporting the first hypothesis. Unexpectedly, stem galls had more similarities between them than to their host organ, hence only partially supporting the second hypothesis. Similarity among stem galls may be caused by the restrictive pattern of host stems. The opposite trend was observed for host leaves, which generate either similar or distinct gall morphotypes due to their higher phenotypic plasticity. The Relative Distance of Plasticity Index for non‐galled stems and stem galls ranged from 0.02 to 0.42. Our results strongly suggest that both tissue plasticity and gall inducer identity interact to determine plant developmental patterns, and therefore, final gall structure.     

Life history strategy and taxonomic position of gall midges (Diptera: Cecidomyiidae) inducing leaf galls on Styrax japonicus (Styracaceae)

Four gall midge species (Diptera: Cecidomyiidae) that induce leaf galls on Styrax japonicus (Styracaceae) were identified to generic level based on larval morphology. Three of these gall midges, which induce whitish hemiglobular galls, flattened subglobular galls, and purple globular galls, respectively, were identified as three genetically distinct species of Contarinia, and the remaining species, which induces globular galls with dense whitish hairs, was identified as a species of Dasineura. Field surveys in Fukuoka, Japan, revealed that adults of these gall midges emerged and oviposited in late March to mid‐April at Mount Tachibana (approximately 200 m a.s.l.) and in late April to early May at Mount Sefuri (about 1050 m a.s.l.), coinciding with the leaf‐opening season of S. japonicus. Larvae of these gall midges mostly developed into third instars by June and then left their galls and dropped to the ground. These species therefore have a life history strategy that differs from that of another S. japonicus‐associated gall midge, Oxycephalomyia styraci, which overwinters as the first instar in ovate swellings, matures rapidly in spring, and emerges directly from the galls.     

Oxycephalomyia, gen. nov., and life history strategy of O. styraci comb. nov. (Diptera: Cecidomyiidae) on Styrax japonicus (Styracaceae)

A new genus Oxycephalomyia is described to contain the gall midge that was previously known as Asteralobia styraci (Shinji). Oxycephalomyia styraci, comb. nov., produces leaf vein galls on Styrax japonicus (Styracaceae). The adult of O. styraci is redescribed, and its full‐grown larva and pupa are described for the first time. The annual life cycle of the gall midge in northern Kyushu was clarified; the first instars overwinter in the galls on the host plant. However, the galls of O. styraci mature much later in the season than those of other gall midges with a similar life history pattern, and the durations of second and third larval instars are remarkably short. Such a life history pattern is considered to have an adaptive significance in avoiding larval parasitism, particularly by early attackers. The number of host axillary buds as oviposition sites decreased in bearing years and increased in off years, but there was no sign of oviposition site shortage even in bearing years, probably due to the low population density of the gall midge. An unidentified lepidopteran that feeds on galled and ungalled host buds and a Torymus sp. that attacks pupae of O. styraci were recognized as mortality factors of the gall midge.     

Nine new species of Dasineura (Diptera: Cecidomyiidae) from flowers of Australian Acacia (Mimosaceae)

Abstract. Thirteen species of Australian acacias are invasive plants in agricultural and native vegetation areas of South Africa. Biological control programmes for Australian acacias in South Africa have been implemented and are aimed at suppressing reproductive vigour and, in some cases, vegetative growth of these weeds. Gall-forming midges are under consideration as potential biological control agents for invasive acacias in South Africa. Entomological surveys in southern Australia found a diverse cecidomyiid fauna associated with the buds, flowers and fruits of Acacia species. Nine new Dasineura species are described and two species, D. acaciaelongifoliae (Skuse) and D. dielsi Rübsaamen, are redescribed. The newly described taxa are D. fistulosa sp.n. , D. furcata sp.n. , D. glauca sp.n. , D. glomerata sp.n. , D. oldfieldii sp.n. , D. oshanesii sp.n. , D. pilifera sp.n. , D. rubiformis sp.n. and D. sulcata sp.n. All eleven species induce galls on ovaries and prevent the formation of fruit. Two general types of gall are caused. Type A comprises woody, tubular galls with larvae living inside ovaries (D. acaciaelongifoliae, D. dielsi, D. fistulosa, D. furcata, D. glauca, D. glomerata, D. oldfieldii). Type B includes soft-tissued, globose galls that belong to four subtypes: inflated, baglike, hairy galls with larvae living between ovaries (D. pilifera); pyriform, pubescent swellings with larvae living inside ovaries (D. rubiformis); globose, hairy, swellings with larvae living superficially on ovaries in ovoid chambers (D. oshanesii); and inconspicuous, glabrous swellings with larvae living superficially on ovaries in shallow groovelike chambers (D. sulcata). The gall types are associated with a particular pupation pattern. In type A galls, larvae pupate within larval chambers in galls, whereas in type B galls pupation takes place between ovaries in galls or in the soil beneath the host tree. Gall midges responsible for the same general gall type are morphologically related and differ from species causing the other gall type. Phylogenetic analysis of a 410 bp fragment of the mitochondrial cytochrome b gene supports the division of the gall midge species into two groups except for D. sulcata, which appears as a subgroup of the group causing type A galls. The interspecific divergence values in group A species were between 0.5 and 3.9% with intraspecific divergence estimates of 0–0.2%. Gall midges causing type B galls had interspecific divergence values of 4.6–7.3% and intraspecific divergence values of 0–3.7%. Closely related biology and morphology together with low cytochrome b divergence estimates suggest a more recent speciation in group A when compared with species of group B. Dasineura rubiformis and D. dielsi are proposed as potential biological control agents for Acacia mearnsii De Wild. and Acacia cyclops A. Cunn. ex G. Don, respectively, in South Africa due to their narrow host range and ability to form high population densities that reduce seed formation. Both species produce galls with low biomass, which makes them compatible with commercial exploitation of their host species in Africa.     

Parasitoid and inquiline attack in the galls of four alien, cynipid gall wasps: host switches and the effect on parasitoid sex ratios

1. Four alien cynipid gall wasps of the genus Andricus are established and still spreading in the British Isles. The order, according to the northerliness of their distribution boundary, is: A. corruptrix→A. quercuscalicis→A. lignicola→A. kollari. All four aliens have a sexual generation in spring on Quercus cerris (introduced to Britain) and an agamic generation in autumn on native oak species. 2. For 2 years 1994 and 1995, galls of both generations of the four alien species were sampled at eight sites from the south of England to the north of Scotland to determine the parasitoid and inquiline species that attack the new galls. The spring generations of the invading species shared a parasitoid complex of four pteromalid species. Five species of inquilines and 11 species of parasitoids emerged from the autumn galls. 3. Two colonisation events were recorded for A. lignicola and A. corruptrix. On both occasions, the spring generations were found first at the new sites, indicating that the agamic generation provides the colonisers for these invading species. After colonisation, the galls of both species were attacked by parasitoids in their first season. 4. In spring, the invading species were among the most abundant cynipids at all eight sites. By sampling the whole local community of cynipid galls, it was found that the parasitoid species attacking the spring galls of the invaders seemed to have shifted their attack to the new hosts. 5. The secondary sex ratios of the parasitoid species emerging from the sexual galls of A. quercuscalicis (the smallest of the four) showed a strong and significant male bias at all sites and in both years. Parasitoid emergence from the galls of the sexual generations of the other three species (all about equal in size) was between 60 and 70% male, and variable among sites and between years.     

Gall formation by a spittlebug, Aphelaenus nigripectus (Aphrophoridae: Auchenorrhyncha; Homoptera)

Few spittlebug species are gall formers, but the Homoptera as a whole contain many gall‐forming species in many families. Nymphs of a spittlebug, Aphelaenus nigripectus (Aphrophoridae, Auchenorrhyncha, Homoptera), were observed to induce leaf‐roll galls on cherry trees (Prunus speciosa, P. × yedoensis and P. pendula cv. pendula (Rosaceae)) in late April in Kyoto, Japan. Aphelaenus nigripectus nymphs aggregated on the ventral surface of the young leaves, fed on the ventral (abaxial) midvein, and excreted masses of froth in the rolled leaves. In a field experiment, it was discovered that feeding of A. nigripectus nymphs can induce rolling of the cherry leaves, and that the rolled leaves may provide protection from desiccation to A. nigripectus nymphs. This is the first record of gall‐forming habits in Japanese spittlebugs.     

Mechanisms of hydraulic conductivity in the leaf galls of Meunieriella sp. (Cecidomyiidae) in Avicennia schaueriana (Acanthaceae): does vascularization explain the preferred sites of induction?

• Intralaminar galls of Meunieriella result from ground tissue proliferation in leaves of Avicennia schaueriana, a typical halophytic mangrove. We tested if the preferred sites of gall induction were the midribs and secondary veins (SV) at the basal leaf portion, where the galls were expected to be largest; and if the vascular system in galls and adjacent regions was altered to favour water supply in galls, thus increasing their growth.
• Gall induction sites and gall sizes were quantified according to leaf portions and regions. Anatomical and histometric analyses in vascular and ground tissues of galls and adjacent regions were compared to equivalent regions of non-galled leaves.
• The galls were largest at basal sites on leaves, the midrib and SV. More galls occurred on the apical portion of the leaf, and on the leaf blade and secondary vein regions. Changes in shape and vascular system area, number and diameter of vessel elements were detected in both galls and adjacent regions. Fewer and smaller-sized vessel elements were observed in regions proximal to the galls and inside them.
• Gall size is not related with preferred induction sites, which could be explained by factors such as thermal balance. Alterations in the vascular system indicate reduced hydraulic conductivity in the xylem in the proximal region and inside galls, leading to water leakage to gall parenchyma cells. This compensatory mechanism explains the expansion and proliferation of water storage and spongy parenchyma cells in the galls, explaining the higher growth in more vascularized regions.