Defenders in the North American aphidPemphigus obesinymphae

Summary Gall-inhabiting individuals of the aphidPemphigus obesinymphae act as defenders, protecting other colony members against attack by dipteran and neuropteran larvae that are the primary predators of this species. As first instar nymphs, the progeny of the fundatrix patrol surfaces of galls and adjoining leaves. These first instar nymphs attack potential predators by mounting and grasping them and inserting their stylets. This defensive behavior, which is not exhibited by nymphs in later instars, appears to be effective in reducing predation. The fundatrix typically produces defenders throughout the extended gall-inhabiting phase, and her progeny delay development beyond the defensive first instar stage. By August, galls contain an average of 101 defenders. Early death of the fundatrix reduces the number of defenders in the gall and advances maturation of defenders into winged migrants, which otherwise mature in September and October. InPemphigus, defensive behavior by first instar nymphs appears to have evolved in the context of several types of derived life cycle, each involving an extended gall-inhabiting phase.     

Secondary host generation of the gall aphid Cerataphis jamuritsu (Homoptera)

Colonies of a Cerataphis species with well‐developed horns were found on the rattan Calamus quinquesstinervis in southern Taiwan. The morphology of first instar nymphs from the colonies accorded well with the morphology of first instar nymphs laid by alates of Cerataphis jamuritsu from galls on Styrax suberifolia, indicating that the rattan aphids are the secondary host generation of C. jamuritsu. Although the aphid colonies were attended by ants, the sharp horns of the first instar nymphs suggest that they might attack predators.     

Soldier caste with morphological and reproductive division in the aphid tribe Nipponaphidini

Summary. We investigated demographic, morphological and histological aspects of Distylaphis foliorum, a gall-forming nipponaphidine aphid from Java, Indonesia, whose first instar nymphs had been reported to have enlarged forelegs and attack other insects. The gall inhabitants of D. foliorum consisted of two discrete populations; one developing normally and the other remaining at the first instar. Morphometric analysis identified two types of first instar nymphs; nymphs with relatively long forelegs and slender abdomen, and nymphs with relatively short forelegs and fat abdomen. The former nymphs were found from both young galls and mature galls, while the latter nymphs were from young galls only. Histological analysis strongly suggested a reproductive division in the first instar. In the former nymphs from mature galls, ovaries and mycetomes were degenerate and replaced by well-developed fat body cells. These results indicated that D. foliorum has a morphologically differentiated sterile soldier caste in the first instar. This study is the first report of a soldier caste with morphological and reproductive division in the aphid tribe Nipponaphidini, and suggests that highly specialized soldier castes have evolved at least four times in aphids.Received 25 June 2004; revised 24 September 2004; accepted 11 October 2004.     

Astegopteryx spinocephala (Hemiptera: Aphididae), a new aphid species producing sterile soldiers that guard eggs laid in their gall

Astegopteryx spinocephala sp. nov., a soldier‐producing aphid species forming banana‐bunch shaped galls on Styrax benzoides in northern Thailand, is described. We found that galls of the species are formed in approximately June and last for almost 1 year, and that the aphid completes its life cycle without migrating to secondary hosts. Many alate sexuparae appeared in March/April, when many sexuals (arostrate males and rostrate females) and eggs were found in live subgalls guarded by soldiers that plugged the ostiole with their sclerotized, spiny heads. Two healthy galls sampled in April contained 2799 and 2659 eggs, respectively. Many live galls were still found in May, and some at the beginning of June. These galls contained both active soldiers and eggs, some of which had already hatched. This indicates that soldiers of A. spinocephala guard eggs until they hatch in at least some 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.     

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.     

Life history,damage assessment and control of Trioza hopeae (Hemiptera: Psylloidea), a serious pest on Hopea odorata (Malvales: Dipterocarpaceae) in Vietnam

Young plants of the commercially important timber species Hopea odorata Roxb. are seriously damaged by the psyllid Trioza hopeae Burckhardt & Vu in nurseries in South Central and Southern Vietnam. Farmers routinely use Class 1 toxic insecticides to control the psyllids but these pose serious health risks in the urban environment. As a precursor to developing a pest management strategy, we studied the life cycle of T. hopeae and trialed several control measures. Trioza hopeae is polyvoltine with overlapping generations peaking in mid wet season. Females laid approximately 135 eggs; however, there was a natural attrition rate of about 80% in first‐instar nymphs due to the nymph's inability to find a suitable feeding site. Feeding nymphs induced pit galls on young H. odorata leaves and were present on all trees examined during the study. The pre‐adult life cycle lasted approximately 13 days and adult life span approximately seven days. Several toxic insecticides were found to be effective for controlling T. hopeae, but a novel non‐toxic alternative was equally as effective. We discuss these methods and potential biological control measures.     

Implications of early production in an invasive forest pest

相似文献   

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.     

Defense by a few first-instar nymphs in the closed gall ofdinipponaphis autumna (homoptera, aphididae, hormaphidinae)

The defensive behavior of the aphidDinipponaphis autumna, which forms small, completely closed galls on leaves ofDistylium racemosum, was observed. In mature galls, in addition to tens of mature or nearly mature aphids of the 3rd generation, there remained 3 – 17 1st-instar nymphs of the same generation, which had well-sclerotized legs and the antennae with developed setae. Despite their minority, these 1st-instar nymphs clung to experimentally introduced insect larvae and stung them with their stylets. Fourth-instar wingpadded nymphs, the majority of the 3rd generation at the experiment, also attacked the introduced larvae, but they were readily spilt from the larvae. Four out of 205 1st-instar nymphs remaining in mature galls had the next instar cuticle developing inside, indicating that they are not destined to be sterile.     

Maternal death relaxes developmental inhibition in nymphal aphid defenders

In certain aphids, first-instar nymphs defend their gall by attacking intruding arthropod predators. One correlate of such defensive behaviour is a lengthened duration of the first nymphal stadium during the galling phase of the life cycle. A prolonged first stadium allows a large army of first-instar defenders to accumulate, which may be advantageous for gall defence. The factors determining developmental delay have been unclear, however. Our field experiment with Pemphigus obesinymphae, a North American gall-forming aphid with defensive first-instar nymphs, tests whether first-stadium duration is influenced by the death of the colony''s fundatrix (mother). We killed fundatrices in certain galls, left those in control galls alive, and counted aphids in each stadium in each gall. Galls in which fundatrices were killed contained a lower proportion of first-instar defenders and more late-instar nymphs than did galls with living fundatrices, indicating that maternal death dramatically increased developmental rate of nymphs. Possibly nymphal aphids respond adaptively to environmental cues that signal a threat to the colony''s welfare. Alternatively, the fundatrix actively suppresses offspring development in order to maintain a large army of soldiers to protect her gall. The results add a new layer of complexity to our understanding of social aphid systems.     

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.     

Altruistic defenders in a gall-forming aphid of the tribe Hormaphidini (Homoptera,Aphididae, Hormaphidinae) on its primary host

Summary. We found defensive behavior in the aphid Hamamelistes miyabei on its primary host plant, Hamamelis japonica, where it forms a spiny gall. Introduction of moth caterpillars into the galls elicited attacking behavior of aphid nymphs with their stylet. Although older nymphs sometimes attacked, first-instar nymphs were the main defenders. Immature and mature galls contained a large proportion of first-instar nymphs. Open galls still contained first-instar nymphs, but the proportion was remarkably smaller. In immature and mature galls, particularly, the molting rate of first-instar nymphs was significantly lower than that of older instars. These data suggest that the defensive strategy of H. miyabei is such that 1) molting of first-instar nymphs is suppressed, 2) the duration of the first instar is prolonged, 3) the proportion of defender nymphs in the gall is elevated, and 4) consequently the colony in the gall is effectively defended against predators. No morphological differences were found either between attacking and non-attacking first-instar nymphs or between molting and non-molting first-instar nymphs. Some first-instar nymphs in open galls had the next instar cuticle developing inside the body. These data suggest that first-instar nymphs of H. miyabei are monomorphic defenders, and that at least some of them are able to develop and reproduce. In addition to the attacking behavior, first-instar nymphs of H. miyabei performed characteristic behaviors such as gall cleaning and hindleg waving. This is the first time that altruistic defenders are described in the primary host generation of an aphid from the tribe Hormaphidini.     

Life‐history parameters and predation capacity of Macrolophus pygmaeus and Nesidiocoris tenuis (Hemiptera: Miridae) on eggs of Plutella xylostella (Lepidoptera: Plutellidae)

相似文献   

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.     

Dermaphis coccidiformis sp. nov. (Hemiptera), an aphid species with asymmetrically sclerotized apterae and “winter alates”

Dermaphis coccidiformis sp. nov. (Hormaphidinae: Nipponaphidini) is described from Japan. Apterous adults of the species were found between winter buds (or between a winter bud and a leaf petiole) of the evergreen oaks Quercus glauca, Q. myrsinifolia and Q. salicina. Their morphology is peculiar in that their tergites are heavily sclerotized only in the part that seems to have been exposed to sunlight. The new species is also peculiar in that nymphs to be alates (sexuparae) were found on the upper surfaces of leaves of the host oak only during winter, from December to March or early April, before the bud break of the oak. Our molecular phylogenetic analysis indicated that the new species is closely related to Dermaphis spp., therefore it was placed in the genus. The analysis incidentally indicated that “Dinipponaphis” autumna, a monoecious species forming galls on Distylium racemosum, was included in the clade of the genus Dermaphis, and therefore it was transferred to this genus.     

Effects of a juvenile hormone analogue, pyriproxyfen, on the apterous form of soybean aphid (Aphis glycines)

The soybean aphid, Aphis glycines Matsamura, is an eastern Asian soybean [Glycine max (L.) Merr.] pest which can reduce soybean yield. We determined the effects of pyriproxyfen, a juvenile hormone analogue, on development, mortality, longevity and fecundity of A. glycines under laboratory conditions. Distance Insect Growth Regulator, containing ∼11.2% pyriproxyfen, was applied at two concentrations, 50 and 150 mg/l, to first and fourth instar nymphs. When first or fourth instar A. glycines were treated with pyriproxyfen, some nymphs became supernumerary‐molted nymphs with 1–3 extra molts or were sterilized. Mortality of treated first instar nymphs was >68% greater than the control group and longevity was reduced by >40%. The higher concentration of pyriproxyfen reduced fecundity of first instar nymphs when they reached adulthood by ∼79%. Pyriproxyfen similarly affected fourth instar nymphs. Mortality of treated fourth instar nymphs was ≥15% greater than the control group and longevity was reduced by >24%. Both concentrations of pyriproxyfen lowered the fecundity of fourth instar nymphs by >27%. Pyriproxyfen also had other sublethal effects on fourth instar nymphs which became apparent when they molted to adulthood. In a few instances they developed wing pads and many produced dead, deformed or abnormal neonates that lacked appendages.     

Life Cycle and Synchronization of Nymphal Development of the Mayfly Ephoron shigae in Japan (Ephemeroptera: Polymitarcyidae)

The life cycle of E. shigae, including eclosion, nymphal growth, last instar recruitment and adult emergence, was studied in a Japanese river. The synchronization of nymphal development is discussed. Eggs hatched sporadically from mid-March to early April as determined from continuous sampling of eggs from the river substratum. Nymphs attained the last instar in mid- to late August and emerged in mid-September. Size of nymphs at the time of last instar recruitment decreased gradually as did the size of emerging mayflies. Smaller individuals entering the last instar later developed more quickly and required a smaller number of degree-days to complete the last instar than did larger individuals. Consequently, larval development synchronized during the period between last instar recruitment and adult emergence.     

Host plant effects on the development and survivorship of the galling insect Neopelma baccharidis (Homoptera: Psyllidae)

In this study, the mortality factors acting upon the galling psyllid Neopelma baccharidis Burckhardt (Homoptera) caused by its host plant, Baccharis dracunculifolia De Candole (Asteraceae) were analysed. In March 1999, 982 galls of the same cohort were randomly marked on 109 individuals of B. dracunculifolia in the field. Galls were censused each month during their development, from April to August, and dead galls were collected and analysed for mortality factors. Gall dehiscence rates were calculated for each month. The major mortality source of N. baccharidis was gall dropping (13.2% of the original cohort), which is probably a normal outcome of previous mortality caused by the other factors observed in this study. Unknown factors killed 11.7% of this gall population and were ascribed to plant resistance during gall development. Empty galls represented 7.7% of the observed mortality and may be a consequence of egg retention or egg mortality/abortion related to variations in plant quality. Shoot mortality was high during the dry season and killed 7.5% of the galls, but this impact was minimized after the third month from gall formation due to the ability of nymphs to accelerate development and emerge from galls on dying shoots. However, the size of dehisced galls on dead shoots tended to be smaller, possibly affecting adult performance. Mortality of N. baccharidis attributed to B. dracunculifolia strongly controlled the galling insect population, killing 40.7% of the original cohort of galls. Plant‐mediated mortality was caused by often neglected factors acting predominantly during the first 3 months of development, which are critical to gall survivorship. These results reinforce the importance of bottom‐up forces in plant‐insect systems.     

Post‐gall induction performance of Adelges Abietis (L.) (Homoptera: Adelgidae) is influenced by clone,shoot length,and density of colonising gallicolae

1. We evaluated the effect of clone (one susceptible and one resistant clone), shoot length, crown level, and gallicola density on post‐gall induction performance of Adelges abietis. Galls that had been successfully induced by one fundatrix on a range of shoot sizes were selected, and the number of gallicolae that could colonise the gall was manipulated. 2. Post‐induction gall development success was inversely related to shoot length and was higher on the susceptible clone than on the resistant clone. As gallicola density did not influence the proportion of galls that successfully completed development, reduced post‐induction gall development on large shoots was not likely to be result of an insufficient stimulus from gallicolae. 3. Clone was the only factor that significantly influenced gall volume and galls were larger on the susceptible clone than on the resistant clone. As gall volume did not increase when more gallicolae attempted to colonise a gall, competition within a gall increased. Gallicola survival was inversely related to the number of colonising gallicolae. Our results suggest that gall size may be limiting at natural densities. 4. Previous studies report positive relationships between gall induction success and fundatrix density, and between gall size and fundatrix density. As each fundatrix produces one egg mass of gallicolae, this study suggests that there may be a trade‐off between the successful induction of a large gall and subsequent survival of gallicolae. 5. In the present study, clone influenced all measures of post‐gall induction performance. Performance was always higher on the susceptible than on the resistant clone.