Tuberaphis owadai (Homoptera), a new aphid species forming a large gall on Styrax tonkinensis in northern Vietnam

Tuberaphis owadai sp. nov., an aphid species forming coral‐shaped galls on Styrax tonkinensis in northern Vietnam, is described. We found that the species produces many sterile second‐instar soldiers in the gall. The colony size of a large gall was estimated to be 178 000, approximately half of which were soldiers. Alates emerging from galls contained sexual embryos, indicating that the life cycle is monoecious (non‐host‐alternating). Predaceous larvae of the pyralid moth Assara seminivalis were found in several galls.     

Formation of long‐lasting galls by overwintered nymphs in the Japanese aphid Quadrartus yoshinomiyai (Hemiptera: Aphididae: Hormaphidinae)

This paper examines the life history of a generation of galls created by the aphid Quadrartus yoshinomiyai (Hormaphidinae: Nipponaphidini) on its primary host plant, Distylium racemosum. First‐instar fundatrix nymphs of Q. yoshinomiyai initiated galls on stems of developing shoots in early April and incipient enclosed galls were found from later the same month. The galls lasted for up to 14 months, during which they grew to maturity, opened in early or mid‐April of the following year and dried up by the end of June. First‐instar fundatrix nymphs were found on winter buds, indicating that they hatched from eggs in autumn and overwintered as nymphs. These results suggest that Q. yoshinomiyai has a three‐year life cycle.     

Female production within the gall and male production on leaves by individual alates of a social aphid

The social aphid Astegopteryx spinocephala forms a banana-bunch shaped gall, consisting of several subgalls, on Styrax benzoides in northern Thailand. The aphid’s life cycle is non-host alternating. Alates (sexuparae) containing both male and female embryos appear near the end of the dry season, when many sexuals and eggs are found in subgalls guarded by sterile soldiers. Our experiments revealed that these alates give birth to almost all (99%) females within the natal subgall before flying but most (73–86%) males on leaves of the host tree after flying, and that these first-instar males intrude into live subgalls for mating. The fact that some (14–27%) males are deposited in the natal subgall indicates the occurrence of both outbreeding and inbreeding, or some level of local mate competition (LMC), in this mating system. However, the primary (investment) sex ratio was estimated to be near 0.5. This suggests that factors other than LMC, a candidate for which is local resource competition, might also affect the sex ratio in A. spinocephala. Received 19 March 2007; revised 12 July 2007; accepted 13 August 2007.     

The aphid Ceratovacuna nekoashi (Hemiptera: Aphididae: Hormaphidinae) and its allied species in Korea,Japan and Taiwan

The aphid Ceratovacuna nekoashi and its allied species have been a taxonomically difficult group. They form peculiar “cat's‐paw” galls (called “Nekoashi” in Japanese) on Styrax trees and also use Microstegium grasses as their secondary hosts. Through sampling aphids from both Styrax galls and Microstegium grasses in South Korea, Japan and Taiwan, and sequencing their DNA, we made it clear that four distinct species occur in these regions: C. nekoashi (Sasaki), C. oplismeni (Takahashi), C. orientalis (Takahashi) and C. subtropicana sp. nov. In Korea, C. nekoashi forms galls on both S. japonicus and S. obassia, whereas in Japan the species forms galls on the former but not on the latter; our molecular analyses unequivocally indicated the occurrence of a single species in South Korea and mainland Japan. Aphids of the four species on the secondary host were morphologically discriminated from one another. The identity of the primary‐ and secondary‐host generations was also clarified for each species. All four species were found to produce second‐instar sterile soldiers in their Styrax galls, and first‐instar soldiers were found in colonies of C. subtropicana on the secondary host.     

Social parasitism and behavioral interactions between two gall-forming social aphids

We investigated ecological and behavioral aspects of the interactions between two social aphids, Pseudoregma bambucicola and Astegopteryx bambucifoliae (Hormaphidinae, Cerataphidini), both of which produce second-instar, sterile soldiers in galls formed on Styrax suberifolius, in Taiwan. By censusing their galls, either species was found to invade galls of the other species. Twenty-eight (58%) out of 48 A. bambucifoliae galls contained P. bambucicola, while four (6%) of 69 P. bambucicola galls contained A. bambucifoliae. Furthermore, P. bambucicola behaved like social parasites in galls of A. bambucifoliae. Colonies of P. bambucicola produced much fewer or even no soldiers compared with those in natal galls. Our experiments also revealed that individual aphids of P. bambucicola more successfully intruded into galls of A. bambucifoliae than into conspecific galls, and that guarding soldiers of P. bambucicola effectively prevented aphids from invading their galls and permitted only conspecific soldiers to join their colonies. These differences in behavior provide good explanations for the differences in the frequency of invaded galls found between the two species. Received 4 September 2007; revised 7 January 2008; accepted 17 January 2008.     

The effects of host-plant properties on gall density,gall weight and clone size in the aphidAploneura lentisci (Pass.) (Aphididae: Fordinae) in Israel

Summary Samples of shoots ofPistacia lentiscus carrying galls of the aphid,Aploneura lentisci, were collected at three localities in Israel. Shoots growing near pruning scars carried more galls than elsewhere on the plant, but these galls weighed less and contained fewer aphids (smaller clones). The proportion of empty galls increased with gall density. Crowding of galls at such sites may be due to the early burst of buds at the time of aphid emergence from the overwintering eggs, and not to active search for preferred sites. Shoots bearing larger numbers of leaves carried heavier galls, which contained larger aphid clones. The position of the galled leaf on the shoot had no effect on gall weight nor on clone size. The physiological condition of the plant may be an important environmental (ecological) factor affecting the variation in clone-size and in aphid morphology among galls.     

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.     

The life history of a gall‐inducing mite: summer phenology,predation and influence of gall morphology in a sugar maple canopy

• 1 Eriophyoid mites are among the most ubiquitous gall‐inducing arthropods, and are adapted species‐specifically to a broad diversity of plants, although their life histories remain poorly studied outside agricultural systems.
• 2 We examined the seasonal phenology of a leaf‐galling eriophyid mite, the maple spindle gall mite Vasates aceriscrumena (MSGM), in naturally occurring stands of sugar maple Acer saccharum in south‐central Ontario in 2007 and 2008.
• 3 Galls were first induced in spring (mid‐May) and were devoid of mites by late August. In the study region, MSGM appears to have at least two generations, with overwintering, deutogyne females that initiate galls in spring (mid‐May) after leaf flush, giving rise to a generation of protogyne (primary) females and a few morphologically similar males (<1 for every 10 females) and, subsequently, to a new generation of deutogyne females in mid‐July to early August. In July, some galls can be highly crowded, with 50–200 individuals per gall.
• 4 In addition, a tarsonemid mite, Tarsonemus acerbilis, was found in approximately 40% of MSGM galls examined. As much as 95.4% of galls in 2007 and 97.4% in 2008 that contained tarsonemid larvae did not contain MSGM eggs (by contrast, only 2.3% of tarsonemid‐free galls contained no MSGM eggs), suggesting that these juveniles feed, at least opportunistically, on MSGM eggs.
• 5 Gall ostiole morphology appeared to influence both MSGM and Tarsonemus densities within galls, with ‘open’ ostioles (versus ‘closed’) being much more susceptible to invasion by the tarsonemid. The latter is likely to be an important regulator of MSGM populations. We hypothesize that the two ostiole types are the result of selection pressures on the gall inducer, favouring closed gall entrances for increased protection, and possibly also on the host tree, favouring open galls to increase predator access.

     

Do aphid galls provide good nutrients for the aphids?: Comparisons of amino acid concentrations in galls among Tetraneura species (Aphididae: Eriosomatinae)

Some aphid species induce leaf galls, in which the fundatrix parthenogenetically produces many nymphs. In order to ensure high performance, galls have to provide the aphids with sufficient nutrients, in particular, amino acids as a nitrogen source. We tested this hypothesis using six Tetraneura aphid species that induce closed galls. We extracted free amino acids from the whole gall tissues of unit weight and quantified the concentration of each amino acid. There were large differences in the total amino acid concentrations among galls of the Tetraneura species. Tetraneura species in which higher concentrations of total amino acids were found in the gall tended to produce larger numbers of offspring. Of the amino acids found, asparagine was predominant in the gall. The asparagine concentration in T. yezoensis galls was several hundred times as high as in control leaves. We discussed why such a high level of asparagine accumulates in aphid galls.     

The impact of kleptoparasitic invasions on the evolution of gall-size in social and solitary Australian Acacia thrips

Many species of gall-inducing Acacia thrips are attacked by kleptoparasitic thrips who enter the gall, destroy the occupants, and then use the gall for producing their own offspring. The hypothesis tested here is that pressure exerted by ldeptoparasites （genus Koptothrips） not only provoked the evolution of soldiers in the gall-inducing clade, but have also influenced the evolution of gall size and morphology. Various size dimensions of invaded galls were compared to those of uninvaded galls using data from six gall-inducing species and their kleptoparasites. For the non-social gall-inducing species （K. ellobus and K. nicholsoni） invaded galls showed no significant size differences from galls that had not been invaded. For the four social gall-inducingspecies （K. habrus, K. intermedius, K. waterhousei and K. morrisi） invaded galls were significantly narrower and/or shorter than uninvaded galls. Galls of social species that had not been invaded and contained adult soldiers were significantly larger than galls where soldiers were still at a larval stage, suggesting that gall size is related to gall age in these species. An hypothesis is proposed that links the timing of invasion by kleptoparasites to size of the host gall： induction of a smaller gall by host founders will reduce the period of vulnerability to invasion （before soldiers become adults） for social thrips by allowing foundresses in these smaller galls to begin laying soldierdestined eggs relatively sooner.     

Factors Influencing Realized Sex Ratios in Fig Wasps: Double Oviposition and Larval Mortalities

Pollinator fig wasps (Agaonidae) are a model system for studies of sex ratio evolution. They lay their eggs in galled ovules within figs. Only one adult emerges from each gall, suggesting that only one egg is always laid per ovule, but if double oviposition occurs then the assumption that adult (realised) sex ratios of fig wasps are representative of primary sex ratios may be violated. Many galls also fail to produce any wasps. If they initially contained eggs then differential mortality rates may also modify realized sex ratios. We investigated whether Kradibia (= Liporrhopalum) tentacularis foundresses in Ficus montana figs avoid laying in ovules that already contain eggs. Comparisons of oviposition frequencies and wasp emergence frequencies showed that most galls that failed to produce wasps will have had eggs laid in them, but few occupied ovules contained two eggs. Realised sex ratios therefore do not necessarily reflect primary sex ratios in this species, but double oviposition is not responsible.     

Aphid galls accumulate high concentrations of amino acids: a support for the nutrition hypothesis for gall formation

The nutrition hypothesis for the adaptive significance of insect gall formation postulates that galls accumulate higher concentrations of nutritive compounds than uninfested plant tissue, resulting in a high performance of the gall former. This hypothesis has been supported by some taxa of gall insects, but not by taxa such as cynipid wasps. Aphid galls are expected to require higher levels of nitrogen than other insects’ galls with a single inhabitant, because aphid galls are required to sustain a number of aphids reproducing parthenogenetically over two generations. The present study tested this hypothesis by evaluating aphid performance and amino acid concentration in phloem sap, using the aphid Rhopalosiphum insertum (Walker) (Homoptera: Aphididae), which establishes colonies on leaves of Sorbus commixta Hedlund or in galls of the aphid Sorbaphis chaetosiphon Shaposhnikov (Homoptera: Aphididae). We prepared the gall and non‐gall treatments on trees of S. commixta, in which R. insertum fundatrices were reared and allowed to reproduce. In S. chaetosiphon galls, R. insertum colonies propagated more rapidly, and the second generation grew larger and more fecund than on ungalled leaves. The amount of amino acids exuding from cut galled leaves was fivefold that in ungalled leaves; however, there was no significant difference in the amino acid composition between galled and ungalled leaves. In the intact leaves, total amino acid concentration in the phloem sap declined rapidly from late April to late May; however, the galls retained this high amino acid concentration in developing leaves for 1 month. These results indicate that the improved performance in R. insertum is ascribed to the increased concentration of amino acids in galled leaves. We suggest that S. chaetosiphon galls function to promote the breakdown of leaf protein, leading to an increased performance of gall‐inhabiting aphids.     

Head-plug defense in a gall aphid

The aphid Astegopteryx sp. forms a banana-bunch shaped gall consisting of several subgalls on Styrax benzoides in northern Thailand, and completes its life cycle on the tree, without migrating to secondary hostplants. We found that its soldiers had sclerotic, protruded heads with many spine-like setae, and that several soldiers cooperate to plug the ostiole of the subgall with these heads. Of 173 ostioles examined in the field, 90.8 % were plugged with no space among the guarding soldiers. Many eggs and sexuals were found within subgalls guarded by soldiers, and a number of males were found trying to intrude into these subgalls. However, they were blocked by guarding soldiers, and it was no easy task for them to intrude into subgalls. The same was true for some soldiers that had rushed out of the subgall. Guarding soldiers often prevented outside soldiers from coming back into the subgall. These findings suggest an interesting possibility that guarding soldiers might consequently select still active, reusable soldiers and strong males for sexual females in their subgall. Received 6 March 2005; revised 5 and 20 July 2005; accepted 27 July 2005.     

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.     

Differential response of trees and shrubs to browsing and pruning: the effects on Pistacia growth and gall-inducing aphids

The effects of long term browsing on growth and morphology of P. atlantica trees and P. palaestina shrubs, and on the colonization of these hosts by their respective gall-inducing aphid guilds, were studied in natural vegetation pastures in Israel. To simulate apical dominance release by browsing, trees and shrubs were pruned and observed one year later. P. atlantica responded strongly to browsing, producing a crown of dense and sharp dry branches and thorn-like shoots, and pruning, compensating or overcompensating for the lost biomass in the studied morphological variables. Morphological responses of P. palaestina were less evident: we found no compensation in most variables. Three species of aphids produced more galls on browsed than on control shoots of P. atlantica. Two species induced more galls on pruned shoots. The five aphid species on P. palaestina colonized browsed and unbrowsed shoots equally, and produced fewer galls on pruned shoots. The role of apical dominance in architectural responses of trees and shrubs to browsing and pruning, as related to resource availability and timing, is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Clonal mixing in the soldier-producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae)

Illuminating the genetic relationships within soldier-producing aphid colonies is an essential element of any attempt to explain the evolution of the altruistic soldier caste. Pemphigus spyrothecae is a soldier-producing aphid that induces galls on the leaf petioles of its host (trees of the genus Populus). At least a quarter of the aphids within the clonally produced gall population are morphologically and behaviourally distinct first-instar soldiers that defend the gall population from predation. Using field trapping and microsatellites, we investigated the degree of clonal mixing within natural gall populations. Field trapping in the UK showed that all the migrants of P. spyrothecae and of two other Pemphigus species were wingless first-instar soldiers. The average degree of mixing estimated from trapping P. spyrothecae migrants was 0.68% (range = 0-15%). Microsatellite genotyping of 277 aphids from 13 galls collected in Italy revealed an average mixing level of 10.4% (range = 0-59%). Six galls contained more than one clone (range = 2-5 clones). Non-kin aphids were not restricted to the soldier caste but were evenly distributed across instars. An additional gall, from which 527 occupants were genotyped, contained 12 non-kin aphids distributed among nine clones, showing that clonal diversity can be high even when mixing is very low. These observations suggest that although soldiers migrate regularly and can moult and reproduce within foreign galls, clonal mixing in this species is generally low and is unlikely to provide a barrier to the evolution of investment by the aphid clones in an altruistic soldier caste.     

An aphidiine parasitoid Monoctonia vesicarii (Hymenoptera: Braconidae) and three chalcidoid hyperparasitoids of Pemphigus matsumurai (Homoptera: Aphididae) forming leaf galls on Populus maximowiczii in Japan

More than 300 unopened leaf galls formed by the pemphigine aphid Pemphigus matsumurai on Populus maximowiczii were collected at Nakasatsunai, Hokkaido, Japan, in July and September 2007 and kept in cold conditions during winter. From mummified fundatrices in the galls an aphidiine parasitoid Monoctonia vesicarii and three species of hyperparasitoids belonging to Pteromalidae, Eupelmidae and Eulophidae emerged from March to May 2008. Monoctonia vesicarii, which is new to Japan, is redescribed. The eulophid hyperparasitoid is described as a new species, Aprostocetus (Aprostocetus) doronokianus, and the pteromalid and eupelmid hyperparasitoids are identified as Pachyneuron sp. and Eupelmus sp., respectively. Approximately 180 unopened mummies of P. matsumurai were dissected in August and November 2008 and a living larva of M. vesicarii was found in each of 17 of them. These observations suggest that some individuals of M. vesicarii pass through two‐year cycles. The implications of the three species of hyperparasitoids to P. matsumurai galls are discussed.     

Spatio-temporal patterns of mortality in Pemphigus populicaulis and P. populitransversus on cottonwoods

Summary Galls of the aphid species Pemphigus populitransversus and P. populicaulis from a single cottonwood in Clinton, New York were censused for mortality approximately every ten days during the summer of 1978. P. populitransversus had significantly higher survival than P. populicaulis. Both species of aphid showed considerably elevated mortality later in the season. Mortality was not spatially random, but neighboring galls had a tendency to die at close to the same time. This tendency to spatially autocorrelated mortality varied from time to time, being more pronounced earlier in the season than later. Later in the season, galls on the outer portions of branches tended to have a higher mortality rate than galls closer to the main trunk of the tree. This effect was highly significant in P. populicaulis, but only suggestive in P. populitransversus.The proportion of dead galls in samples of the two species taken at other times and places was consistent with the data from the censuses. In addition, the potential of two common predators, Anthocoris sp. and Leucopis sp., for producing autocorrelated mortality in Pemphigus was assessed in these collections. There was some association of Leucopis with regions of higher mortality, but this was not the case in Anthocoris. Leucopis tended to be found in galls of P. populicaulis more frequently than in P. populitransversus unlike Anthocoris, suggesting that some of the differential mortality between P. populitransversus and P. populicaulis might be due to this dipteran predator.     

Secondary galling: a novel feeding strategy among ‘non‐pollinating’ fig wasps from Ficus curtipes

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Social aphids use their antennae to perceive density cue for soldier production

In social insects, local interactions among colony members facilitate information transfer, and allow the whole colony to regulate division of labor and task allocation in an integrated and coordinated manner. In particular, regulation of caste differentiation in response to external cues is important for sustaining social insect colonies. The social aphid Tuberaphis styraci exhibits a caste polyphenism, producing second‐instar soldiers and non‐soldiers. Previous studies using an artificial diet rearing system identified high aphid density as a crucial cue for soldier production, which acts on embryos in the maternal body and newborn first‐instar nymphs to induce soldier differentiation. While direct contact stimuli from live non‐soldiers were suggested to mediate the density effect, how the aphids perceive the stimuli has been unknown. Here we investigated how antennal removal of adult females affects the soldier production in T. styraci. Under a high density condition, intact females produced the highest percentage of soldiers, females deprived of both antennae produced the lowest percentage of soldiers, and females deprived of one antenna exhibited an intermediate percentage of soldiers. Scanning electron microscopic observations of the aphids revealed the existence of sensory organs for chemoreception and tactile sensation on the antennae of the mother aphids. These results indicate that T. styraci females use their antennae to perceive soldier‐inducing density cue, suggesting that maternal perception of density cue is involved in regulation over caste phenotype of their offspring.