Three new records of the subfamily Aphidiinae (Hymenoptera: Braconidae) from Korea

Three species of the Aphidiinae (Hymenoptera: Braconidae) are reported for the first time in Korea: Aphidius rhopalosiphi de Stefani-Perez, 1902, Aphidius uzbekistanicus Luzhetzki, 1960 and Lysiphlebus orientalis Starý and Rakhshani, 2010. Their diagnosis, photographs and host list are included.     

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.     

Diversity of Natural Enemies of Aphids Belonging to Aphidiinae (Hymenoptera: Braconidae) in India

An inventory of the biodiversity of aphidiine parasitoids (Hymenoptera: Braconidae) associated with aphids in India showed 123 species under 23 genera to be intensively and extensively exercising natural control. The inventory has been reinforced with all associated details, mainly zoogeographical distribution, parasitism potential attributes and other such relative details from primary sources so as to make it serve as an important startup tool for planning any IPM strategy, involving biocontrol of aphids.     

Quality of different aphids as hosts of the parasitoid Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae)

Lysiphlebus testaceipes (Cresson) has a broad aphid host range; however the quality of these preys may interfere in its biological feature. This study aimed to evaluate the quality of three Macrosiphini, Brevicoryne brassicae (L.), Lipaphis erysimi (Kaltenbach) and Myzus persicae (Sulzer), and three Aphidini Schizaphis graminum (Rondani) Rhopalosiphum maidis (Fitch) and Aphis gossypii Glover as hosts to L. testaceipes and to determine the relation possible of host preference, of size and quality of the host. The tests were carried out in climatic chamber at 25 +/- 1 degrees C, RH 70 +/- 10% and 12h photophase. The parasitoid did not oviposite in B. brassicae and L. erysimi, while the other species were nutritionally suitable to the parasitoid. L. testaceipes showed preference for aphids from tribe Aphidini and these hosts presented better quality to the parasitoid when compared to Macrosiphini. Interactions among size, preference and quality between the Aphidini were found. L testaceipes showed preference (parasitism rate 76.7%) for R. maidis, the bigger host (hind tibia with 0.281 mm). This host provided bigger size (hind tibia with 0.49 mm) and higher emergence rate (95.6%) to the parasitoid when compared to A. gossypii (parasitism rate of 55.7%). Also the smaller host A. gossypii (0.266 mm) provided smaller size hind tibia (0.45 mm) and higher mortality of the parasitoid (emergence rate 72.1%). However, the development time was shorter and the longevity was higher in A. gossypii (6.3 and 5.4 days, respectively) when compared to the host R. maidis (6.7 and 3.8 days, respectively), and not been related to host size.     

Evolutionary relationships of wing venation and wing size and shape in Aphidiinae (Hymenoptera: Braconidae)

We explored evolutionary changes in wing venation and wing size and shape in Aphidiinae, one of the well-known groups of parasitic wasps from the family Braconidae. Forewings of 53 species from 12 genera were examined, for which a molecular phylogeny was constructed on the basis of the mitochondrial barcoding gene COI. By covering all types of wing venation within the subfamily Aphidiinae and by using landmark-based geometric morphometrics and phylogenetic comparative methods, we tested whether evolutionary changes in wing shape correlate to the changes in wing venation and if both changes relate to wing size. The relationship between wing morphology and host specificity has been also investigated. We found that six types of wing venation, with different degree of vein reduction, could be recognized. Wing venation type is largely genus specific, except in the case of maximal reduction of wing venation which could be found across examined Aphidiinae taxa. The reconstruction of evolutionary changes in wing venation indicates that evolutionary changes in wing shape are related to the changes in wing size, indicating that miniaturization play a role in evolution of wing morphology while host specialization does not affect the wing shape within the subfamily Aphidiinae.     

Quality of different aphids species as hosts for the parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae: Aphidiinae)

The suitability of Macrosiphum euphorbiae (Thomas), Aulacorthum solani (Kaltenbach) and Acyrthosiphon kondoi Shinji (Hemiptera: Aphididae) as hosts for the aphid parasitoid Aphidius ervi Haliday was evaluated by assessing host size, host preference, and host quality. Tests were carried out in an environmental chamber at 22±1oC, 70±10% RH and 12h photophase. Replicates (11) consisted of one 24h-old mated female of A. ervi without a previous oviposition experience. Female was released into a Petri dish (5 cm) with 20 2nd and 3rd instars of one of each aphid species tested on a leaf disc of the host plant onto a 1% water-agar layer. Parasitoid emergency was lower in A. kondoi (78.7%) compared to M. euphorbiae (92.2%) and A. solani (91.7%). Acyrthosiphon kondoi (0.36 mm) was the smallest host. The parasitoid showed preference (74.0% parasitism) for M. euphorbiae, the largest host (hind tibia length=0.73 mm), which in turn yielded larger A. ervi females (0.75 mm).     

A comparison of techniques used to study the morphology of final instar larvae of aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae)

Abstract. The morphology of the head sclerites of final instar larvae of aphid parasitoids prepared from cast larval skins and excised heads of whole larvae are compared, using both optical and scanning electron microscopy. Remarkable differences in the apparent shape of head sclerites, particularly mandibles, were found. Some of these differences are probably due to a consistent dorso-ventral flattening of the head during moulting, observed in cast skin preparations, whereas excised heads tend to flatten antero-posteriorly. The importance of these findings for understanding the three-dimensional shape of final instar mandibles and for the study of larval morphology and taxonomy of Hymenoptera is discussed     

Molecular identification of Aphidius transcaspicus (Hymenoptera: Braconidae: Aphidiinae), a closely associated species of Aphidius colemani,in Korea

Aphidius colemani (Braconidae: Aphidiinae) is an endoparasitoid and one of the most commercially used parasitoids for the control of various pest aphids. However, species identification of A. colemani is difficult because of the high degree of morphological similarity with closely associated species, such as A. transcaspicus and A. platensis. Recently, we identified a large-scale emergence of parasitoids from mummies of Rhopalosiphum maidis on barley banker plants in Yecheon County, Korea. The morphological characteristics of the forewing, petiole, and antenna indicated that our specimen is A. transcaspicus. The partial nucleotide sequence analysis of the mitochondrial cytochrome oxidase subunit I (COI) gene showed that it is 100% identical to Japanese specimens and 1.69% variable to Greek specimens. Analysis of the phylogenetic tree, haplotypes, and amino acid sequence of the COI gene, as well as the internal transcribed spacer 2 (ITS2) of the nuclear ribosomal DNA region, indicated that A. transcaspicus is closer to A. platensis than A. colemani, and Korean and Japanese populations were mostly diversified groups at the intraspecific level. This study provides important information to elucidate the genetic variation in A. transcaspicus and the relationships between closely related species within the A. colemani group.     

Aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) in cultivated and non-cultivated areas of Markazi Province, Iran

The fauna of aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae), as well as their diversity and tritrophic (parasitoid-host aphid-host plant) associations in cultivated and non-cultivated areas of Markazi province, was studied during 2004–2009. Thirty species of Aphidiinae belonging to 9 genera were identified. There are presented, in total, 73 associations with 32 host aphids occurring on 42 host plants. Five parasitoid-aphid associations are newly recorded from Iran. Lysiphlebus cardui (Marshall) is newly recorded for the fauna of Iran. Lysiphlebus fabarum (Marshall) and Diaeretiella rapae (M’Intosh) were the most abundant species in non-cultivated (72.96%) and cultivated (41.17%) areas, respectively. In the non-cultivated areas, L. fabarum was found on eight aphid species, while in cultivated areas it was only found on Aphis craccivora Koch. In cultivated areas, Sitobion avenae (F.) has the greatest diversity of parasitoids (Shanon-Weiner H = 0.875) whereas in non-cultivated areas the greatest diversity of parasitoids was recorded upon Acyrthosiphon pisum (Harris) (Shanon-Weiner H = 1.149). Significant differences were found between diversity of two ecosystems based on the overall diversity indices. Both species diversity and evenness were greater in cultivated ecosystems. The results are discussed in relation to the over-all parasitoid-aphid-plant associations in the area.     

Fertility life table of Aphidius colemani Viereck (Hymenoptera: Braconidae, Aphidiinae) on Aphis gossypii Glover (Hemiptera: Aphididae)

The intrinsic rate of increase of a parasitoid related to its hosts play an important role in biological control programs. In this work, fertility of the parasitoid Aphidius colemani Viereck was evaluated on Aphis gossypii Glover by means of a fertility life table. To determine the immature mortality, the development time and the sex ratio, 12 mated females of A. colemani (24h old), and 240 nymphs of A. gossypii (3 days old) were used. To evaluate fertility 15 mated females (24h old) were used. For each parasitoid female, 300 nymphs were offered in the 1st day, 250 nymphs in the 2nd day, 200 nymphs in the 3rd day, 150 nymphs in the 4th day, 100 nymphs in the 5th day and 50 nymphs in the other days. Immature mortality of A. colemani was 22.1%, development time of males and females were 12.0 and 11.8 days, respectively, and sex ratio was 0.6. The females of A. colemani laid 420 eggs and had longevity of 5.9 days. The net reproduction rate (R(o)) was 194.81 females and the intrinsic rate of increase (r(m)) was 0.384 females/females/day. The finite rate of increase (lambda) was 1.48 females/day, the mean length of a generation (T) was 13.74 days and the time to duplication the population (TD) was 12.60 days. The parasitoid A. colemani had a great potential of population growth on A. gossypii as a host and could be an effective biological control agent of this aphid.     

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.     

A review of the West Palaearctic aphidiines (Hymenoptera: Braconidae: Aphidiinae) parasitic on Uroleucon spp., with the description of a new species

A review of aphidiine wasps (Hymenoptera: Braconidae) parasitizing the Uroleucon species in the West Palaearctic is presented. Eleven species are keyed and illustrated. In addition, a new hymenopteran parasitoid species: Praon nonveilleri n. sp. from Uroleucon inulicola (Hille Ris Lambers) infesting Inula ensifolia L., is described. The new species is diagnosed and illustrated. It belongs to the “dorsale-yomenaé” species group and was collected from the Djetinja canyon in Serbia and Montenegro. The aphidiines presented in this work were identified from 97 aphid taxons occurring on 236 plant taxons. Furthermore, 361 original parasitoid – host aphid – host plant associations of the species mentioned in the key are presented. Finally, phylogenetic relationships inside the “dorsale-yomenae” species group and related species were reconstructed using cladistic distance methods.     

Phylogenetic relationships among genera of Aphidiinae (Hymenoptera: Braconidae) based on DNA sequence of the mitochondrial 16S rRNA gene

Phylogenetic relationships among forty‐nine taxa representing twenty‐four genera of Aphidiinae (Hymenoptera: Braconidae) were investigated using DNA sequence of a portion of the mitochondrial 16S rRNA gene and parsimony analysis. Seven species in six other subfamilies of Braconidae were used as outgroup. The results suggested that members of Aphidiinae are monophyletic. The basal lineage of Aphidiinae was Aclitus in weighted and unweighted parsimony analyses and Praini was basal relative to Ephedrini. With the exception of Pauesia and Aphidius, all genera were monophyletic. The results support generic status for Euaphidius, but not for Lysaphidus. Diaeretus leucopterus was internal to a clade composed of three Pauesia species, suggesting that the latter genus may be paraphyletic. A combined analysis that included DNA sequence of 16S rRNA, NADH1 dehydrogenase and 28S rRNA resulted in more robust cladograms with topologies similar to those inferred from the 16S rRNA gene sequence alone. The results are compared to previously proposed phylogenies of Aphidiinae based on morphological and molecular characters.     

Praon Haliday (Hymenoptera: Braconidae: Aphidiinae) of Southeastern Europe: key, host range and phylogenetic relationships

A review of species in the genus Praon Haliday, 1833 is presented. Twenty described species are keyed and illustrated with scanning electron micrographs and line drawings. The Praon species presented in this work have been identified from 67 aphid taxa occurring on 120 plant taxa. Furthermore, 87 original parasitoid–aphid–plant associations of the species mentioned in the key are presented. Phylogenetic relationships among Praon species are reconstructed using parsimony and cladistic distance methods. Praon abjectum is the sister taxon to the remaining Praon species. We recognized three species group: “Parapraon”, “dorsale-yomenae” and “rosaecola”. Monophyly is suggested for “Parapraon” species group and paraphyly for “dorsale-yomenae” group. Finally, by phylogenetic reconstruction, a close phylogenetic relationship between “Parapraon” and “dorsale-yomenae” species group was found.     

Characterization of the genus Aspilota (Hymenoptera: Braconidae)

ABSTRACT. The alysiine braconid genus Aspilota Foerster is redefined to include Dinotrema Foerster. Characters previously used to delimit both Dinotrema and species groups within Aspilota s.l. are discussed, with emphasis on difficulties in interpreting transformation series. Dinotrema amplisignata (Fischer), Dinotrema phoridarum (Goidanich) and Dinotrema nigricornis (Thomson) are returned to Aspilota.     

Brood-size and sex-ratio variation in field populations of three species of solitary aphid parasitoids (Hymenoptera: Braconidae, Aphidiinae)

Solitary parasitoids of colony-forming hosts may produce quasi-gregarious broods, which favours sibmating on the natal patch and local mate competition (LMC). We examined seasonal variations in brood size and sex ratio in three species of solitary parasitoids of aphids associated with trophobiotic ants. Adialytus arvicola, a parasitoid of Sipha agropyrella on grasses, had the smallest broods (mean=4.2, maximum 19), while Lysiphlebus hirticornis, a parasitoid of Metopeurum fuscoviride on tansy, had the largest broods (mean=32.0, maximum 265). In Pauesia pini, a parasitoid of Cinara piceicola on Norway spruce, broods comprised an average of 5.8 (maximum 41) individuals; brood size increased during early summer when hosts became more available but remained the same later in the season. In all three species the sex ratio at eclosion was female-biased, with broods containing approximately two daughters for each son in both A. arvicola and L. hirticornis; the degree of female-bias was least in P. pini. The sex ratio did not vary with brood size. In A. arvicola, the variance of the number of sons declined with an increase in brood size, consistent with "precise" sex allocation. In contrast, in L. hirticornis, the overall sex-ratio variance was greater than its binomial expectation, while it did not differ from binomial in P. pini. A large proportion of broods contained only sons or only daughters, especially in A. arvicola. An excess of male-only broods is expected if constrained females (which can produce only sons) contribute offspring prior to mating. The number of male-only broods, however, did not differ from the number expected if all females are mated and allocate offspring sexes binomially, except in P. pini. In the latter species, broods with two daughters (as opposed to two sons) exceeded binomial expectations. We propose that P. pini is largely outbreeding, while the strongly female-biased sex ratio in A. arvicola and L. hirticornis is consistent with partial sibmating and LMC. Ant-parasitoid interactions could account for a different population mating structure in the three parasitoid species. Both A. arvicola and L. hirticornis mimic the epicuticular hydrocarbon pattern of their aphid hosts. Eclosing wasps are ignored by honeydew-collecting ants and hence can mate and forage on the natal patch. In contrast, P. pini generally depart the mummy area to avoid attacks by trophobiotic ants and mate off patch.     

Mating system of Bracon hebetor (Hymenoptera: Braconidae)

Abstract.

• 1 We report on the mating system of a field population of the parasitic wasp, Bracon hebetor, on a corn pile infested by the Indian meal moth, Plodia interpunctella. We demonstrate that the mating system is based upon male scramble competition polygyny with male aggregations on high places on the corn.
• 2 The sex ratio among adults was greater than 80% males on the surface of the corn, whereas below the surface the sex ratio was less than 45%. Males actively courted females on the surface, but there were no aggressive interactions among males during courtship or mating.
• 3 Approximately 20% of the females found on the surface of the corn had no sperm in their spermathecae, regardless of age, but the numbers of unmated females decreased later during the day.
• 4 In laboratory studies we showed that females from this population oviposit a female biassed sex ratio, and that only 14% of females were mated before dispersing from their place of emergence.
• 5 Thus sib-mating is unlikely in this gregarious parasitoid. This outcrossing mating system probably arose because of severe inbreeding depression that B.hebetor suffers via a sex locus: diploids that are heterozygous at the sex locus develop into females, but homozygous diploids are male and are generally inviable. The female biassed sex ratio may have evolved in B. hebetor in response to males being the more expensive sex, females dispersing more frequently from the population than males, or a fraction of females remaining unmated in the population.