Larval competition between Aphidius ervi and Praon volucre (Hymenoptera: Braconidae: Aphidiinae) in Macrosiphum euphorbiae (Hemiptera: Aphididae)

Interspecific competition between parasitoid larvae may influence the size, structure, and stability of the population, leading to a reduction in total parasitism and thus restricting the pest control. Aphidius ervi (Haliday) and Praon volucre (Haliday) are endoparasitoids that possess a wide host range and present considerable potential for the biological control of the aphid Macrosiphum euphorbiae (Thomas). The larval competition between A. ervi and P. volucre, and the possible intrinsic competitive superiority of one of the parasitoids in M. euphorbiae, have been studied. In single parasitism experiments, mated parasitoid females (n=10) were maintained individually in contact with M. euphorbiae hosts (n=30) inside petri dishes containing lettuce leaf discs and maintained in environmental chamber at 22 ± 1°C, 70 ± 10% RH, and 12-h photophase. The multiple parasitism experiments consisted of exposing single parasitized aphids (n=120) to the second parasitoid species. Two oviposition events were performed with a 4-h interval between them, namely the following: sequence A (oviposition by A. ervi, followed by P. volucre) and sequence B (oviposition by P. volucre, followed by A. ervi). Oviposition sequence A generated 24 A. ervi and 55 P. volucre adults, whereas oviposition sequence B generated 23 and 49 adults. P. volucre is an intrinsically superior competitor compared with A. ervi, and the use of the two species simultaneously may result in competitive exclusion and influence the stability of the parasitoid population.     

Consequence of emergence pattern on inbreeding risk in the aphid parasitoid Aphidius matricariae (Hymenoptera: Braconidae)

In insect parasitoids, mating strategy depends on mate availability and is influenced by the spatial and temporal emergence patterns of adults. For quasi-gregarious species, simultaneous emergence favors local mating and reduces search costs for partners while increasing the risk of inbreeding, particularly when only one female parasitizes the initial host patch. Consequently, in inbreeding sensitive species, mating on the place of adult emergence (patch mating) between siblings should be counter selected. In practice, the timing of male and female emergence and of their dispersal influences mate availability and can limit on patch mating. To test the role of these two factors, we analyzed the daily distribution of emergence and patch residence time of a cohort in the aphid parasitoid Aphidius matricariae (Hymenoptera: Braconidae). We observed that adult emergence is concentrated on the morning with males emerging on average before females with some overlaps. A more precise evaluation of emergence pattern within a brood suggests that brothers and sisters rarely emerge at the same time and rapid dispersal of males and females favors off-patch mating. The relationships between timing of emergence including differences between sex and consequences on inbreeding probability in these species are thus discussed.     

Biological parameters and thermal requirements of the parasitoid Praon volucre (Hymenoptera: Braconidae) with Macrosiphum euphorbiae (Hemiptera: Aphididae) as host

The effect of temperature on the biology of Praon volucre (Haliday, 1833) (Hymenoptera: Braconidae) in Macrosiphum euphorbiae (Thomas, 1878) (Hemiptera: Aphididae) hosts was studied and the thermal requirements of the parasitoid were determined. Experiments were carried out at 16, 19, 22, 25, and 28 ± 1°C with 70 ± 10% relative humidity and 12 h photophase. The developmental time of P. volucre males and females decreased between 16 and 23°C. The highest percentages of aphid parasitism and adult parasitoid emergence were observed at 16, 19, and 22°C. The sex ratio (expressed as % females) decreased between 16 and 23°C. Male and female longevity was high between 19 and 22°C and decreased strongly at 25°C. The lower temperature threshold for P. volucre was 5.17°C and the thermal constant was 243 degrees-days.     

Age-dependent functional response of Aphidius matricariae (Hymenoptera: Braconidae) on tobacco aphid,Myzus persicae nicotianae (Hemiptera: Aphididae)

This study was performed to investigate the age-dependent functional response of Aphidius matricariae Haliday (Hymenoptera: Braconidae) at varying densities of tobacco aphid, Myzus persicae nicotianae Blackman (Hemiptera: Aphididae). Six densities (2, 4, 8, 16, 32, and 64 numbers) of third instar nymphs of M. persicae nicotianae were daily exposed to one pair of 1-day-old A. matricariae until the parasitoid female died. Each host aphid density was replicated 10 times. The experiments were conducted at constant environmental conditions (25 ± 1 °C, 70 ± 5% RH and 16:8h L:D photoperiod). The logistic regression model demonstrated that the functional response of A. matricariae was type III in the second day and type II in the first day and from third to the end of adult parasitoid lifetime. The handling time (T_h) was lowest in the first day (0.2305 h) and highest in the sixth day (2.9296 h) of the parasitoid’s life. The searching efficiency (a) values were 0.0573, 0.0649, 0.0503, 0.0229, and 0.0077 h^?1 in the first, third, fourth, fifth, and sixth days of the parasitoid’s life, respectively. Also, the b value for type III functional response was 0.0147 in the second day. The values of maximum attack rate (T/T_h) ranged from 104.12 nymphs/24 h in the first day to 19.8 nymphs/24 h in the sixth day of parasitoid’s life. Based on the results, A. matricariae showed a high potential to control the population of tobacco aphid and the highest efficiency gained in the first half of the female parasitoid life.     

Interspecific competition between two endoparasitoids Cotesia vestalis (Hymenoptera: Braconidae) and Oomyzus sokolowskii (Hymenoptera: Eulophidae)

Two endoparasitoids, Cotesia vestalis and Oomyzus sokolowskii, parasitize the same host, larvae of Plutella xylostella. These two species have evolved different parasitization strategies. O. sokolowskii expresses a single factor, venom, and exerts virtually no detrimental effects on the development of its host. C. vestalis, on the other hand, injects polydnavirus (PDV) and venom during oviposition, and teratocytes are released into the host's hemolymph after egg hatching. Parasitization suppresses host immune reactions and redirects its developmental program. Because both these species parasitize the same stage of their hosts, there is the possibility of multiparasitism in nature. Only one species survives multiparasitism and because of its parasitic strategy, we hypothesized that C. vestalis would invariably be the stronger competitor. We designed competition experiments which revealed that C. vestalis is a stronger competitor than O. sokolowskii. We also show that C. vestalis survives intrinsic competition with O. sokolowskii through two mechanisms: physical attack and physiological suppression. We discovered melanized wounds on O. sokolowskii eggs and larvae, which is strong evidence of physical attacks. The physiological suppression is due to PDV and venom injected by C. vestalis. To test this idea more rigorously, we designed a pseudoparasitization experiment which revealed that no O. sokolowskii emerged from multiparasitized hosts when infertile C. vestlais eggs and normal O. sokolowskii larvae are both present inside the same host. These results support our hypothesis that C. vestalis is the stronger competitor and demonstrate two mechanisms that account for the outcome of intrinsic competition between these two endoparasitoids.     

Density-dependent parasitism of cowpea aphid,Aphis craccivora by Lysiphlebus fabarum,Binodoxys acalephae,and Aphidius matricariae (Hymenoptera: Braconidae: Aphidiinae)

Biological control, as a major component of pest management strategies, uses natural biological agents to reduce pest populations. Studying the interaction among Aphis craccivora and its parasitoids including, Lysiphlebus fabarum, Binodoxys acalephae, and Aphidius matricariae in 2016 and 2017 in Tehran Parke-Shahr, showed positive, significant correlations in all cases between the densities of three parasitoid species and that of aphid nymphs and adults. The density of the parasitoids increased by increasing the density of the aphids. The parasitoids showed aggregative behavior in response to different densities of the host. There was a positive density-dependent correlation between the density of A. craccivora and rate of parasitism. Parasitism rates of nymphs and adult aphids by L. fabarum, B. acalephae, and A. matricariae increased or decreased along with decline or increase in the population of the aphid host. In 2016 spring, the highest rates of parasitism on aphid nymphs by L. fabarum, B. acalephae, and A. matricariae were 46.82, 23.09, and 17.16%, respectively. In 2017 spring, the highest rates of parasitism on aphid nymphs by L. fabarum, B. acalephae, and A. matricariae were 48.97, 21.77, and 15.06%, respectively. So, given the accordance between changes in aphid population and that of parasitoids, and parasitoids’ efficacy in Tehran’s polluted air, they can be used as biological agents in the management of A. craccivora population.     

Functional responses of aphid parasitoids,Aphidius colemani (Hymenoptera: Braconidae) and Aphelinus asychis (Hymenoptera: Aphelinidae)

We evaluated the functional responses of two aphid parasitoids: Aphidius colemani on the green peach aphid Myzus persicae (Hemiptera: Aphididae), and Aphelinus asychis on M. persicae and the potato aphid, Macrosiphum euphorbiae (Hemiptera: Aphididae). Parasitoid oviposition occurred at host densities of 5, 10, 20, 30, 50, 80 or 100 aphids for A. colemani and 5, 10, 20, 30 or 50 aphids for A. asychis. More M. persicae were parasitized by A. colemani than by A. asychis at an aphid density of 50. Among the three types of functional response, type III best described the parasitoid response to the host densities both in A. colemani and A. asychis. The estimated handling time was shorter for A. colemani than for A. asychis (0.017 and 0.043 d, respectively). The proportion of aphids that were parasitized exhibited the same characteristic curve among the three host-parasitoid combinations: a wave form that appeared to be a composite of a decelerating (as in type II) response at low host density and an accelerating-and-decelerating (as in type III) response at medium to high host density. We hypothesize that the novel host species (and its host plant), density-dependent superparasitism, and/or density-dependent host-killing may have induced the modified type III response.     

红火蚁与两种本地蚂蚁间的干扰竞争

为了探讨重大入侵生物红火蚁Solenopsis invicta Buren与本地蚂蚁的竞争机制以及红火蚁成功入侵的机理, 本研究以红火蚁和2种本地蚂蚁黑头酸臭蚁Tapinoma melanocephalum (Fabricius)及亮红大头蚁Pheidole fervida Smith为材料, 室内测定了红火蚁分别与黑头酸臭蚁、亮红大头蚁之间在个体水平和种群水平上的攻击性和攻击强度。一对一攻击试验结果表明：红火蚁和黑头酸臭蚁之间攻击级别多集中在Ⅲ级, 即竞争优势明显的红火蚁对黑头酸臭蚁缺乏激烈的攻击, 只是在相互攻击时多摆出威胁姿势; 红火蚁与亮红大头蚁之间攻击性较强, 尤其是红火蚁中型和小型工蚁与亮红大头蚁兵蚁之间的攻击性（3.35和3.30）显著强于红火蚁大型工蚁与亮红大头蚁兵蚁的攻击性（2.70）。群体攻击试验结果表明：与黑头酸臭蚁群体攻击的红火蚁各处理组合中, 无死亡红火蚁出现, 而黑头酸臭蚁死亡率为31.80%; 而与亮红大头蚁群体攻击中, 红火蚁死亡率为0.20%~12.00%, 而亮红大头蚁平均死亡率为49.91%。可见, 红火蚁的群体攻击能力强于黑头酸臭蚁和亮红大头蚁, 其中红火蚁与亮红大头蚁间的相互攻击程度激烈, 死亡率较高, 而与黑头酸臭蚁间的攻击程度较弱, 可能由于黑头酸臭蚁化学防御对本身起到一定的保护作用, 这为进一步加强红火蚁发生区本地蚂蚁优势种--黑头酸臭蚁的保护利用提供理论基础。     

Apparent competition between two species of aphid via the fungal pathogen Erynia neoaphidis and its interaction with the aphid parasitoid Aphidius ervi

Abstract 1. Motivated by a community study on aphids and their fungal pathogens, three hypotheses were tested experimentally to investigate the influence of the fungal pathogen, Erynia neoaphidis Remaudière and Hennebert, on aphid population and community ecology.
2. Field experiments were performed in 2 years to test whether two susceptible aphid species on different host plants might interact through the shared fungal pathogen. No strong pathogen-mediated indirect interactions (apparent competition) between populations of pea aphid Acyrthosiphon pisum Harris and nettle aphid Microlophium carnosum Buckton were detected.
3. In the first of the field experiments, pea aphids exposed to the fungus showed a weak tendency to produce more winged dispersal morphs than control populations not exposed to the fungus. In a laboratory test, however, no support was found for the hypothesis that the presence of volatiles from fungus-infected cadavers promotes production of winged offspring.
4. The response of the pea aphid parasitoid Aphidius ervi Halliday to colonies containing hosts infected 1 and 3 days previously was assessed. Wasps initiated fewer attacks on 1-day-old infected colonies than on healthy colonies, with the numbers on 3-day-old fungus-infected colonies intermediate.     

Multiparasitism of the green peach aphid, Myzus persicae: competition in the egg stage between Aphidius matricariae and Ephedrus cerasicola

Multiparasitism of the green peach aphid, Myzus persicae (Sulzer) by the solitary aphidiid parasitoids Aphidius matricariae Haliday and Ephedrus cerasicola Starý was studied in the laboratory at 22°C. Single aphids first stung by an A. matricariae female were then offered to a female of E. cerasicola 1, 2 or 3 days later. E. cerasicola oviposited without restraint in such aphids. The multiparasitized aphids were dissected 3 or 4 days after the Ephedrus parasitization or allowed to mummify.Only a single parasitoid, either egg or larva, was found in a dissected host. The relative frequency of the two species was roughly the same in dissection series as in corresponding mummification series. When E. cerasicola oviposited 1 or 2 days after A. matricariae, E. cerasicola was the intrinsically superior species. Dissection showed that the competition occurred at least one day before the Ephedrus egg hatched, and that very few eggs of A. matricariae hatched in such aphids. Apparently, the Aphidius eggs must have been killed by substances injected by the ovipositing Ephedrus female or by substances or structures connected with the Ephedrus egg itself. When E. cerasicola oviposited 3 days after A. matricariae, A. matricariae survived. Probably its 4th instar larvae devoured the eggs of E. cerasicola together with the other host contents.Interspecific competition without larvae involved has not previously been demonstrated in Aphidiidae.

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Résumé L'étude du multiparasitisme de Myzus persicae (Sulzer) par les parasitoïdes Aphidiidae solitaires, Aphidius matricariae Haliday et Ephedrus cerasicola Stary a été réalisée à 22°C. Des pucerons isolés, piqués par une femelle de A. matricariae avaient été proposés ensuite à une femelle de E. cerasicola, 1, 2 ou 3 jours plus tard. E. cerasicola a pondu sans restriction dans de tels pucerons.Des témoins constitués de pucerons piqués par A. matricariae ont permis de déterminer le pourcentage des pucerons piqués, réellement parasités par A. matricariae. Les pucerons parasités une ou plusieurs fois ont pu se mommifier ou ont été disséqués 3 ou 4 jours après avoir été parasités par Ephedrus.Les fréquences relatives de développement des deux espèces, obtenues par dissection ou par étude des mommies, ont été rigoureusement les mêmes. Quand A. matricariae avait pondu 1 ou 2 jours avant E. cerasicola, A. matricariae s'est développé dans au moins 15% des pucerons apparemment multiparasités, contre 60 à 70% dans les témoins. Chez ces pucerons multiparasités, E. cerasicola était un compétiteur intrinsèquement supérieur. Quand A. matricariae avait pondu 3 jours avant E. cerasicola, A. matricariae survivait et se développait dans environ 70% des pucerons multiparasités. Chez ces pucerons, les oeufs d'E. cerasicola avaient probablement été dévorés avec le contenu de l'hôte par les larves âgées d'A. matricariae.Les oeufs des parasitoïdes sont difficiles à observer dans l'hôte les premiers jours après la ponte. Un seul parasitoïde, oeuf ou larve, était découvert lors de la dissection du puceron. La conclusion en a été que la compétition en faveur de E. cerasicola s'est produite quand les deux espèces étaient sous forme d'oeuf et au moins un jour avant l'éclosion d'Ephedrus. On peut en déduire que les oeufs d'A. matricariae sont tués par des substances injectées par la femelle de E. cerasicola lors de la ponte.Une compétition interspécifique n'impliquant pas les larves n'avait jamais été démontrée chez les Aphidiidae.

     

Intraguild Predation by Anthocoris nemorum (Heteroptera: Anthocoridae) on the Aphid Parasitoid Aphidius colemani (Hymenoptera: Braconidae)

The magnitude of intraguild predation by adult females of the predator Anthocoris nemorum on immature larvae of the aphid parasitoid Aphidius colemani inside mummies of peach-potato aphids Myzus persicae was investigated under laboratory conditions in a preference experiment. Each predator consumed a mean (95% confidence limits) of 2.8 (2.1; 3.8) immature parasitoids within mummies and 3.6 (2.7; 4.6) unparasitised aphid nymphs. Thereby A. nemorum engaged in intraguild predation with A. colemani and did not exhibit prey preference between mummies and unparasitised aphids.     

Overwintering strategies and cold hardiness of two aphid parasitoid species (Hymenoptera: Braconidae: Aphidiinae)

The role of winter diapause in two aphid parasitoid species, Aphidius ervi Haliday and Aphidius rhopalosiphi DeStefani-Peres (Hymenoptera: Braconidae: Aphidiinae), in host synchronization and the induction of cold hardiness was investigated. Parasitoids were reared during three successive generations on Sitobion avenae Fabricius, at 15 degrees C under a photoperiod of 9 h light 15 h dark. Although these conditions are known to be strongly diapause inducing, neither parasitoids showed an incidence of diapause above 65% over the three generations; the rest of the population underwent quiescence. In both parasitoid species, diapausing mummies exhibited greater cold hardiness than non-diapausing mummies, resulting in significantly lower supercooling points (SCP) and in a higher survival rate during long-term exposures at 0 and -10 degrees C. The induction of increased cold hardiness in parasitoids was thus associated with the diapause state. SCPs of third instar larvae of S. avenae were similar to those of non-diapausing mummies of both parasitoid species, but significantly higher than those of diapausing mummies. The effect of winter climate on the stability of the host-parasitoid interaction is discussed.     

Suitability of three aphid species for Aphidius gifuensis (Hymenoptera: Braconidae): Parasitoid performance varies with hosts of origin

Oviposition behavior and offspring fitness of the parasitoid Aphidius gifuensis (Ashmead) were compared on three aphid species, Sitobion avenae F., Myzus persicae (Sulzer), and Aphis gossypii Glover using wasps collected from both S. avenae and M. persicae. A. gifuensis produced more mummies and adults on S. avenae and M. persicae than on A. gossypii regardless of the host of origin. Mummy production was influenced by attack rate and percentage of aphids superparasitized. The F₁ generations from S. avenae and M. persicae were more female-biased and wasps were larger than those from A. gossypii. Although there were significant differences in development time of A. gifuensis in the three aphid species, the difference was generally shorter than one day. Fewer mummies were produced when A. gifuensis was transferred between S. avenae and M. persicae, but no significant difference was observed in emergence rate, percentage of female offspring, or body size. The effects of host species on A. gifuensis female performance and offspring fitness are discussed, along with the potential for using A. gifuensis to control M. persicae and A. gossypii.     

闭弯尾姬蜂与菜蛾盘绒茧蜂寄生菜蛾幼虫时的种间竞争

在室内25℃下,以菜蛾3龄初幼虫作寄主,研究了菜蛾盘绒茧蜂Cotesia plutellae和半闭弯尾姬蜂Diadegma semiclausum的种间竞争。当寄主供2种蜂同时产卵寄生时,2种蜂各自的寄生率与其单独寄生时无显著差异,合计寄生率比一种蜂单独存在时有所提高,但差异不显著。2种蜂均能产卵寄生已被另一种蜂寄生了的寄主幼虫。当寄主被2种蜂寄生的间隔时间很短（少于10 h）时,所育出的蜂绝大部分（80%以上）为绒茧蜂;当寄主先被绒茧蜂寄生,并饲养2天以上再供弯尾姬蜂寄生时,所育出的全为绒茧蜂;当寄主先被弯尾姬蜂寄生,并饲养2天以上再供绒茧蜂寄生时,寄主幼虫绝大部分不能存活,只有少部分能育出寄生蜂,且多为弯尾姬蜂。当2种蜂的幼虫存在于同一寄主体内时,2种蜂的发育均受到另一种蜂的抑制;绒茧蜂1龄幼虫具有物理攻击能力,能将弯尾姬蜂卵或幼虫致死。这些结果表明,菜蛾盘绒茧蜂与半闭弯尾姬蜂在同一寄主中发育时,前者具有明显的竞争优势。     

Phototactic behaviour in Aphidius gifuensis (Hymenoptera:Braconidae)

We investigated the spectral sensitivity and response to light intensity of Aphidius gifuensis (Hymenoptera: Braconidae), a key natural enemy of the green peach aphid, Myzus persicae (Hemiptera: Aphididae). We used 15 monochromatic lights (emitting various specific wavelengths from 340 to 689 nm) and white light. Monochromatic light of different wavelengths and white light elicited photopositive behaviour from A. gifuensis. The strongest response was stimulated by blue light (492 nm), which induced a movement of 43.5 cm, a response that differed from all other groups. This was followed by green light (568 nm) and UV-light (380 nm). There was no significant response to orange light (601 nm) or red light (649, 668 and 689 nm) from A. gifuensis. The response intensity curve for A. gifuensis to monochromatic light (492 nm) decreased as light intensity increased. At 568 nm, the phototactic response showed an ‘S’ shaped curve. But at 628 nm, the phototactic response rose continuously with increasing intensity. We report here that the visual system of A. gifuensis is composed of three spectrum receptors, attuned to UV, blue and green light. While light intensity is a key factor in determining the photopositive response of A. gifuensis, the effect of intensity varies by wavelength.     

Interference interactions and nest usurpation between two subordinate ant species

Camponotus foreli (Emery) and Cataglyphis iberica (Emery) are two sympatric, subordinate ant species that have been found to fight in attacks that usually conclude with the death of many workers of both species and with nest abandonment by C. iberica. These harassment episodes have been observed in two different areas and over many years of study. No such attacks of C. foreli were observed in the study areas against any other ant species, nor did any other ants attack C. iberica nests, and laboratory confrontations confirmed this specificity. These attacks neither eliminated C. iberica colonies, nor distanced them from C. foreli nests. Moreover, there was no real competition for food between the species: in an experiment where all C. iberica colonies were eliminated from an area, rates of prey and liquid food collection by C. foreli nests in the exclusion zone were similar to those found in the control zone with C. iberica, and the activity rhythms of C. foreli did not change in the absence of C. iberica. The hypothesis of competition for a nest site is more consistent. Both in the laboratory and the field, the most frequent outcome of these aggressive interactions was the occupation of the C. iberica nest by C. foreli. This behavior may be advantageous for C. foreli, because it is much less skilful at excavating than C. iberica. One of the chief concerns of this study is to show that such interference interactions, typical especially of dominant, very aggressive species, are also found between subordinate, apparently nonaggressive species. Received: 20 March 1997 / Accepted: 29 September 1997     

Male wing fanning by the aphid parasitoid Aphidius ervi (Hymenoptera: Braconidae) produces a courtship song

We, herein, report evidence that wing fanning by the aphid parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) constitutes a courtship song. Complete removal of the forewings or only the distal half of them reduced male copulation success in comparison to intact males. Males that achieved copulation within the observation period produced wing fanning at a higher rate than males that did not copulate. Playback of wing fanning sound altered the behaviour of virgin females, increasing the time they devoted to grooming, as compared with subjects that were exposed to silence or white noise. Our findings contribute to the understanding of the acoustic dimension of the sensory modalities employed by this aphid parasitoid in sexual signalling.