Host-acceptance behaviour of Alloxysta pleuralis, a cynipoid hyperparasitoid of an aphidiid parasitoid Trioxys indicus on aphids

Alloxysta pleuralis parasitizes the larvae of Trioxys indicus, a parasitoid of Aphis craccivora. The pattern of host-searching of A. pleuralis was random regarding the host-stage. Earlier second instar to early fourth instar larvae of T. indicus within the haemocoel of the living aphid were found susceptible for attack, however, the third instar larvae were more parasitized. The rate of oviposition was very low (8.5 eggs/h). The number of pricks into the aphid was significantly more for the aphids that contained susceptible stages of the potential host. The occurrence of superhyperparasitism was lower when the hyperparasitoids were offered a choice of all host stages than were offered no-choice.

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Résumé A. pleuralis est un hyperparasitoïde endophage de Trioxys indicus, parasitoïde d'Aphis craccivora, puceron de Cajanus cajan. Bien que les larves de T. indicus soient susceptibles d'être attaquées du début du second stade au début du quatrième stade, celles du troisième stade sont nettement préférées. L'absence de fifférence entre les fréquences de visites et de contacts avec les hôtes de différents stades a montré que le comportement de prospection de A. pleuralis s'effectue au hasard. Cependant, la fréquence des piqûres/hôte est significativement supérieure chez lez hôtes préférés, ce qui donne une indication sur le fait que A. pleuralis pique un puceron pour rechercher un hôte potentiel. Il est possible que la femelle perçoive la présence de l'hôte dans le puceron en décelant avec les récepteurs sensoiriels de sa tarière les changements physiologiques caractéristiques du puceron parasité, et qu'elle les utilise pour piquer à répétition le puceron jusqu'à ce qu'elle trouve l'hôte potentiel. Le superhyperparasitisme était relativement faible et plus fréquent dans les expériences où l'hyperparasite n'avait pas de choix.

     

Effect of parasitoid density on the functional response and sex ratio of a cynipoid hyperparasitoidAlloxysta pleuralis [Hym.: Alloxystidae]

Experiment where variable densities (1, 2, 5, 10, 25, 50, 100 and 150) of the parasitoid (5–7 d postparasitised aphids (Aphis craccivora Koch). — parasitised by aphidiid parasitoidTrioxys indicus Subba Rao & Sharma) were exposed to individual hyperparasitoidAlloxysta pleuralis (Cameron) indicated following: (1) with increase of initial host (primary parasitoid) densities the number of hosts hyperparasitised increases sigmoidally reaching to a plateau at 50 host similar to thetype 3 functional response of Holling; the curve was described by a logistic eqution [N_hyp=44.0/(1+exp (4.0–0.16 N_p))], (2) greater host mortality was recorded at lower initial host densityes (≤50); (3) the area of discovery of the hyperparasitoid is inversely density-dependent at higher host densities (≥25); and (4) the variation in host number has no significant influence on the sex ratio of F₁ offspring of the hyperparasitoid which ranges between 0.56–0.67. The implications of these responses of the hyperparasitoidA. pleuralis are discussed.      

Host specificity and seasonal distribution of Alloxysta pleuralis, a cynipoid hyperparasitoid of aphids in India

Abstract. 1. Alloxysta pleuralis (Cameron) is a cynipoid (Hymenoptera) hyperparasitoid of aphids (Homoptera) through their aphidiid (Hymenoptera) parasitoids.
2. It was recorded attacking five aphidiids, Lysiphlebus delhiensis (Subba Rao & Sharma), Trioxys indicus Subba Rao & Sharma, Aphidius uzbekistanicus Luzhetzki, Lipolexis scutellaris Mackauer and Lysiphlebia mirzai Shuja-Uddin (in order of preference) out of eight species of aphidiid parasitoids tested.
3. Percentage of hyperparasitism of aphids infesting cucurbits, cereals and pulses is higher than in solanaceous crops. Maximum hyperparasitism was recorded on the T. indicus/Aphis gossypii Glover/cucurbit complex.
4. The aphid host as well as the food plants significantly influence its efficiency.
5. A.pleuralis is abundant in northeastern Uttar Pradesh in winter (December–March) when large areas of pulses, cereals and cucurbits are infested with aphids serving as hosts for the primary parasitoids.     

Bionomics ofTrioxys indicus [Hym.: Aphidiidae], a parasitoid ofAphis craccivora [Hem.: Aphididae]: 31. Effect of host haemolymph on the numerical response of the parasitoid

The influence of kairomones on the numerical response of the parasitoidTrioxys indicus against its hostAphis craccivora at its varying density was studied. The kairomones (applied as aqueous extract of the host) significantly enhanced the rate of parasitisation and multiplication and the area of discovery of the parasitoid and also the K-values of mortality of the host at all parasitoid densities introduced (1, 2, 4, 8, 12 and 16 parasitoids) into troughs having about 200 hosts. The sex-ratio of F₁ offspring decreased at lower parasitoid densities and remained more or less unchanged at higher parasitoid densities after the application of kairomones. The present findings indicate that if kairomones are applied properly, the number of hosts destroyed by a stimulated parasitoid will be about 200, twice the number reported earlier, thus fewer parasitoids will be needed to regulate an estimated population of the hosts.      

Parasitoid-host relationship betweenTrioxys (Binodoxys) Indicus [Hymenoptera: Aphidiidae] andAphis Craccivora [Hemiptera: Aphididae]. VI. Impact of males on the number of progeny of the parasitoid reared on certain host plants

The present paper elucidates the impact of males on the reproductive rate ofTrioxys (Binodoxys) indicus reared on the aphids ofCajanus cajan, Dolichos lablab andSolanum melongena host plants. The F₁ offspring increases with the increase of parasitoid number. This increase is maximum inC. cajan followed byD. lablab andS. melongena reared aphids. The presence of male parasitoids caused a significant decrease in the emergence of F₁ generation.      

Differential Interactions Between an Aphid Endohyperparasitoid and Three Honeydew-Collecting Ant Species: A Field Study of Alloxysta brevis (Thomson) (Hymenoptera: Alloxystidae)

The behavioral interactions between the chemically protected aphid hyperparasitoid Alloxysta brevis and three trophobiotic ant species were examined in the field on thistles. The patterns were not essentially influenced by hyperparasitoid sex. Ants differed in their guarding behavior of aphids and their response toward A. brevis. Lasius niger attacked the hyperparasitoid more readily than Myrmica laevinodis, while aggression by Formica rufa was intermediate. Apart from applying chemical defense, A. brevis responded to ants by flying away (mainly at L. niger) or with avoidance behavior (mainly at M. laevinodis). Additionally, females might switch their tactics from flight to defense with increasing age. Females left the plant more often after encounters with L. niger or F. rufa than with M. laevinodis. Disturbance by any ant species affected the foraging activities, reducing oviposition success to nearly zero.     

Fecundity,reproductive rate,longevity, and intrinsic rate of increase of an aphidiid parasitoidLysiphlebia mirzai

A life-table was constructed for a little known aphidiid waspLysiphlebia mirzai, a parasitoid of cereal aphid,Rhopalosiphum maidis. The female parasitoid survived 6.4 ± 1.17 (SD) days and oviposited intensively 4.0 ± 0.47 days. The total fecundity rate, R_t, was 169.2 ± 6.94 mummies/female and net reproductive rate, R_o, was 92.70 female offspring/female. The intrinsic total fecundity rate, r_t, and intrinsic rate of natural increase, r_m, the finite rate of total fecundity, λ^t, and finite rate of increase, λ^m, was 0.27048, 0.24155, 1.31059 and 1.27322 respectively. The mean generation time (18.75 days) and doubling time of the population (2.87 days) was slightly higher than other aphidiids studied so far. The proportion of female progenies decreased significantly on the successive oviposition days.      

Contact Kairomones Mediating the Foraging Behavior of the Aphid Hyperparasitoid Alloxysta victrix (Westwood) (Hymenoptera: Charipidae)

A variety of host-related substances was assessed in relation to their ability to induce arrestment and antennal examination behavior in adult females of the aphid hyperparasitoid Alloxysta victrix (Westwood). In laboratory bioassays, whole-body homogenates of both unparasitized host aphids [Myzus persicae (Sulzer)] and those parasitized by the primary parasitoid Aphidius colemani Viereck failed to elicit a response. However, significant kairomonal activity was associated with aphid cornicle secretions, aphid honeydew, and solvent extracts of parasitized aphids. Solvent extracts of unparasitized aphids (in either hexane or butan-1-ol) failed to elicit arrestment or antennal examination behavior in hyperparsitoid females. The response to aphid honeydew was significantly lower in experienced females than in naive individuals, suggesting that even relatively strong innate responses can be modified by learning.     

Lysiphlebus testaceipes,an introduced aphid parasitoid in portugal [Hym.: Aphidiidae]

Lysiphlebus testaceipes (Cresson), an exotic parasitoid species introduced in 1973–74 into southern France and subsequently widespread over the whole mediterranean France, Italy and Spain has become established even in Portugal since 1985. It was found on the southern coast of Portugal parasitizingAphis nerii Boyer de Fonscolombe. In 1986 it spread towards the North, its host range expanded and now includesAphis chloris Koch,Aphis citricola van der Goot,Aphis fabae Scopoli,Aphis frangulae Kaltenbach,Aphis gossypii Glover,A. nerii, Aphis parietariae Theobald,Aphis sedi Kaltenbach,Toxoptera aurantii (Boyer de Fonscolombe). The proved complete development and a high parasitization ofL. testaceipes onA. citricola is the 1st case in the whole Mediterranean, from where only incomplete development and a negligible percentage of parasitization (Italy) have been reported. Both the host range composition and development ofL. testaceipes indicate an increase of genetic polymorphism in the established populations. Interspecific relations ofL. testaceipes and the indigenous parasitoid species indicate an increasing dominance of the exotic biocontrol agent.      

Bionomics ofTetrastichus sesamiae [Hymenoptera: Eulophidae], a pupal endo-parasitoid ofMaruca testulalis [Lepidoptera: Pyralidae]

The biology and behaviour ofTetrastichus sesamiae Risbec, a pupal endoparasitoid ofMaruca testulalis Geyer, were studied under laboratory conditions. Most adults emerged from the host pupae between 08.00 h and 09.00 h and mating and oviposition started almost immediately. Both ♂♂ and ♀♀ mated repeatedly, and each ♀ could lay eggs for up to 6 days and in up to 5 host pupae. Progeny production ranged from 0–263 offspring per ♀ and adult longevity was from 4.3–13.9 days. The quality of food available to the adults was a major factor influencing progeny production, and longevity. The species was capable of parasitizing and completing development on pupae of such other major Lepidopteran crop pests asChilo partellus Swinhoe,Busseola fusca Fuller,Eldana saccharina Wlk andSpodoptera exempta Wlk, an important finding for biological control of these pests under intercropped agro ecosystems. Apart from parasitism, ♀♀ ofT. sesamiae also caused considerable mortality by stinging, and presumably paralyzing, host pupae without ovipositing.      

枸杞瘿螨姬小蜂的生物学特性

枸杞瘿螨姬小蜂Cirrospilus eniophyesiYang(新种)是枸杞瘿螨Aceria pallidaKeifer的重要天敌,以幼虫在虫瘿内取食枸杞瘿螨的成虫和若虫。在(25±1)℃下,该蜂完成1个世代需16~21d。成虫寿命及产卵量与补充营养有关,取食10%蜂蜜水的雌虫寿命为(6.94±0.67)d,雄虫为(5.14±0.49)d。不进行补充营养的雌雄成虫寿命分别为(1.96±0.27)d和(1.06±0.29)d;补充10%蜂蜜水和水可显著提高产卵量,每雌平均产卵量分别为(29.13±6.12)粒和(23.14±3.16)粒,产卵高峰期在羽化后的第2天。成虫羽化时间多集中在6:00~8:00am和4:00~6:00pm,羽化当天即可交尾。枸杞瘿螨姬小蜂自然种群消长与寄主虫口密度相关,在6月底7月初寄生率达到83.3%。     

Honeydew as a contact kairomone for aphid parasitoids

Aphidius rhopalosiphi De Stefani-Perez, four other primary parasitoids and three hyperparasitoids of cereal aphids responded to cereal aphid honeydew on filter paper discs by greatly increasing visit times. Both female and male parasitoids responded, females generally more strongly. A. rhopalosiphi females were shown to habituate to honeydew, and to dishabituate fully in 90 min. Their response increased with increasing concentrations of honeydew up to 0.25 mg/l, but no further increase was detected at 0.5 mg/l. The response did not occur when direct contact with the treated paper was prevented. A. rhopalosiphi responded to some honeydew from non-host aphids as strongly as to that from host aphids. A. rhopalosiphi responded to the honeydew produced by Metopolophium dirhodum (Walker) reared on artificial diet and to the diet itself as strongly as to honeydew from M. dirhodum reared on wheat. The response of A. rhopalosiphi to honeydew therefore appears not to be caused by specific plant chemicals in the honeydew, and is probably not caused by aphid-specific chemicals. The results are discussed in relation to host location by A. rhopalosiphi.

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Résumé Les parasitoïdes primaires de pucerons des céréales: Aphidius rhopalosiphi, A. picipes, A. ervi, Praon volucre et Ephedrus plagiator, ainsi que leurs hyperparasitoïdes, Dendrocerus carpenteri, Phaenoglyphis villosa et Alloxysta victrix ont réagi à du miellat de Sitobion avenae imbibant des disques de papier filtre, en prolongeant beaucoup leur temps de visite. Les femelles et les mâles ont réagi, mais les femelles généralement plus fortement. L'augmentation du temps de visite était probablement provoqué par la diminution de leur vitesse dans les zones traitées, leur tendance à séjourner dans ces zones et à y retourner après les avoir quittées.Les femelles de A. rhopalosiphi s'habituaient au miellat, mais s'en déshabituaient totalement en 90 minutes. Leurs réactions augmentaient avec la concentration en miellat jusqu'à 0,25 mg/l, sans qu'il y ait eu une nouvelle augmentation à 0,5 mg/l. La réaction était supprimée en absence de contact direct avec le papier. A. rhopalosiphi a repondu à quelques miellats produits par des non-hôtes aussi fortement qu'à celui de ses hôtes. A. rhopalosiphi a réagi au miellat produit par Metopolophium dirhodum, élevé sur milieu artificiel, et au milieu nutritiflui-même, aussi fortement qu'au miellat de M. dirhodum élevé sur du blé. Ainsi, la réponse d'A. rhopalosiphi à un miellat apparait comme n'étant pas due à la présence de substances chimiques spécifiques de plantes, ni, probablement, à des substances produites par les pucerons. Les résultats sont discutés en relation avec la localisation de l'hôte par A. rhopalosiphi.

     

Interactions between ants attendingAphis fabae ssp.cirsiiacanthoidis on thistles and foraging parasitoid wasps

We describe the behavioral interactions between honeydew-collecting workers of the ants Lasius nigerand Myrmica ruginodisand females of three species of aphidiid wasps (Lysiphlebus cardui, Lysiphlebus testaceipes, Trioxys angelicae)foraging for their aphid host, Aphis fabaessp. cirsiiacanthoidis,on thistles. Using field and laboratory experiments, we show that the ant-parasitoid interactions are species specific. Workers of both ant species generally attacked and killed females of T. angelicae,but they ignored those of L. cardui.This pattern was not altered when we anesthetized the wasps slightly with carbon dioxide to reduce their mobility. Prior contacts between L. carduiand either conspecific L. nigerfrom a different nest or workers of a different ant species (M. ruginodis)did not influence L. niger'snonaggressive behavior. The number of aphids parasitized by L. testaceipeswas significantly reduced in aphid colonies attended by L. niger,although this parasitoid was rarely attacked by ants. In encounters between these species of ants and wasps, ant aggression is consistent with differences in wasp behavior. We suggest that, in addition, chemical cues located in the cuticula may enable L. carduito avoid detection by honeydew-collecting ants.     

Variation in selected life-history parameters of the parasitoid wasp,Aphidius ervi: Influence of host developmental stage

We determined the age-specific fecundity and survival of the solitary parasstoid wasp,Aphidius ervi Haliday (Hymenoptera: Aphidiidae), under constant laboratory conditions. Wasps were reared in each of the four nymphal instars of apterous pea aphids,Acyrthosiphon pisum (Harris) (Homoptera: Aphididae): L₁ (age 24h), L₂ (48 h), L₃ (72 h), and L₄ (120 h). Age-specific survival (l_x) and fecundity (m_x) differed between parasitoids developing in different aphid instars. The wasps’ life-time reproductive success, as indexed by the intrinsic rate of population increase (r_m), varied non-linearly with adult biomass and host size at parasitization. A close agreement between larval growth rates in different host instars and adult reproductive performance suggests that, inA. ervi, fitness correlates may be significantly influenced by larval ontogeny and trade-offs in resource allocation.     

The influence of prior ovipositional experience on host selection in four species of aphidiid wasps (Hymenoptera: Aphidiidae)

We evaluated the influence of prior ovipositional experience on host selection in four solitary parasitoids, Aphidius erviHaliday, A. pisivorusSmith, A. smithiSharma & Subba Rao, and Praon pequodorumViereck (Hymenoptera: Aphidiidae). When provided simultaneously with equal numbers of two species of aphids, Acyrthosiphon pisum(Harris) and Macrosiphum creeliiDavis (Homoptera: Aphididae), all four parasitoids showed a moderate to strong preference for A. pisum.This preference did not increase after sampling, except in P. pequodorum.Learning did not alter host selection behavior in A. erviand P. pequodorum.However, females of A. pisivorusconditioned on A. pisumselected fewer M. creeliithan unconditioned wasps and wasps conditioned on M. creelii.It is suggested that prior ovipositional experience influences a parasitoid's expectations of the kinds of hosts available, but it does not alter the (innate) rank order of hosts.     

Evaluation of an improved method for mass-rearing of thrips and a thrips parasitoid

Improved laboratory methods are described in detail for mass rearing of various thrips species, such as Frankliniella occidentalis, Frankliniella intonsa, Thrips palmi, Thrips tabaci (Thysanoptera: Thripidae) and a thrips parasitoid, Ceranisus menes (Hymenoptera: Eulophidae), using various foods. In one method, plant pollen and honey solution are used as food sources. In a second method, germinated broad bean seeds are used. Eggs, produced in large numbers in water, are collected by a suction funnel onto a filter paper and incubated in a Petri dish. Large numbers of larvae that hatch are collected by using food traps (plant pollen). Larvae can be reared on pollen or on germinated broad bean seeds until adult emergence without additional water and food. This method has been found useful for producing even-aged thrips at different densities (up to 500 larvae in a cage of 80 mm diameter) with relatively low mortality rates. Evaluation of this rearing method for F. intonsa, shows that during 2 weeks at 20 °C per 100 females more than 4000 females could be produced in the next generation. About 5 min per day is required to achieve this productivity of mass production. The method is also suitable for producing large numbers of the solitary endoparasitoid of thrips larvae, C. menes.     

Low field performance of an aphid parasitoid,Aphelinus abdominalis,efficient in the laboratory [Hym., Aphelinidae]

Life history traits of two inbred lines of the aphid parasitoidAphelinus abdominalis (Dalman) were evaluated in the laboratory. Both lines exhibited high fecundities, produced a high proportion of female offspring and showed to be long-lived. However, release experiments in winter wheat fields failed to achieve establishment of the parasitoids. In addition, the wasps parasitized considerably fewer aphids in two types of field cages than they did in the laboratory. AsA. abdominalis eggs and/or larvae arrested in development were not found in dissected aphids from field cages, we conclude that the wasps were unable or unwilling to parasitize high numbers of hosts in the cages. The reason for this odd behaviour is unknown.