Rearing techniques for hornets with emphasis on Vespa velutina (Hymenoptera: Vespidae): A review

Of the 34 vespid species recorded worldwide as invasive aliens, particular attention is currently being given to the yellow-legged hornet Vespa velutina that has invaded Europe, Japan, and Korea. The hornet is a voracious predator of bees and a serious threat to bee colonies and bee pollination. Control measures are needed, but their development has been challenging as biological and ecological studies are limited by the short field season and the cryptic nesting behavior of these hornets. A Vespa rearing process can generate the large numbers of workers, gynes, and males that are essential for studying chemical ecology and life history and for experimental testing of various hypotheses. We present a synthesis of suitable methods and techniques for year-round Vespa hornet rearing. Particular reference is given to Chinese know-how and experience with Vespa rearing for medicinal and culinary motivations. We also draw on observations with reared insects that have a similar life history as Vespa hornets, namely Bombus bumblebees and Vespula yellowjackets. Key challenges to optimizing Vespa hornet rearing are identified and discussed.     

Genetic diversity of genus Vespa including an invaded species of V. velutina (Hymenoptera: Vespidae) in Korea inferred from DNA barcoding data

With about 5000 known species, the Vespidae is a large family belongs to order Hymenoptera. The genus Vespa with 22 species is one of the four genera of the subfamily Vespinae. In Korea, 10 species and subspecies are recognized. Because of their social behavior, their treat to human health and their impact in apiculture, the reliable and sometimes automated identification of these insects to species level are important. To test the efficacy of DNA barcoding method for identification of species of the genus Vespa in Korea, 30 samples of eight Korean species of genus Vespa were collected and mitochondrial DNAs of 658 bp fragment cytochrome oxidase subunit 1 (CO1) region were sequenced. A Bayesian Inference based on COI gene of the Korean Vespa species was constructed. The phylogenetic tree shoed that identification of all specimens is possible based on COI gene and we found strong relation between the sequences of the collected species from different localities in South Korea which clustered together with 100% support with sequences of the same species in GenBank. The results demonstrate that DNA barcoding is a useful technique for rapid and accurate species recognition in Korean Vespa species. The DNA barcode part of COI for V. binghami is provided for the first time that can help for identification of this species through DNA barcoding. Also, the genetic diversity among Korean Vespa velutina was zero suggests that the invasion might have occurred in a single event with small number of founders.     

Distribution,spread, and impact of the invasive hornet Vespa velutina in South Korea

Hornets (Vespa spp) are top insect predators that can control pests, but their venomous stings and defensive behavior cause numerous human deaths throughout Asia. Hornets usually inhabit rural areas which reduces potential conflict with humans. In 2003, the invasive hornet, Vespa velutina, arrived in southern Korea (Yeongdo region) and became established. It is currently spreading northwards at a rate of 10–20 km per year. Despite originating in tropical/subtropical areas of Indo-China, its nesting biology and life cycle in South Korea are similar to those found throughout its native range, with mature colonies containing 1000–1200 adults. In 7 years, V. velutina has become the most abundant hornet species in Southern Korea by displacing native Vespa species such as V. simillima, which has a similar nesting biology. We also found a significant positive correlation between the abundance of V. velutina and the degree of urbanization, indicating that this invasive species was well adapted to urban environments. This was supported by our finding that 41% of emergency call-outs (119 Rescue Services) to deal with social wasps/hornet problems were due to V. velutina, which was twice as high as the number of calls about the next most abundant species. The rapid spread of V. velutina across southern Korea indicates that this species will continue to spread north-westward in the Korean peninsula and will become a major problem as more people and beekeepers come into contact with this aggressive invasive hornet.     

Tracing the invasion characteristics of the yellow-legged hornet,Vespa velutina nigrithorax (Hymenoptera: Vespidae), in Korea using newly detected variable mitochondrial DNA sequences

The yellow-legged hornet, Vespa velutina nigrithorax (Hymenoptera: Vespidae), invaded South Korea in 2003 through Busan metropolitan city, which is located in the southeast region of the country. Previous studies aiming to trace the origin of V. velutina in Korea used a portion of mitochondrial (mt) COI and detected a single haplotype common to the site of origin. However, no subsequent study on invasive dynamics such as additional entry and/or another site of entry has been performed. In this study, segments of mt COI, CytB, and lrRNA were sequenced from 238 individuals collected in 11 Korean and two Japanese localities, but no variation in each gene was observed. Thus, we developed two intergenic spacer (IGS) sequences from the publicly available mt genome of V. velutina, which provided substantially increased variability (i.e., 19 haplotypes with 1.74% maximum sequence divergence in 1,129–1,146-bp-long concatenated sequences). Population genetic analyses using the concatenated sequences unexpectedly provided higher genetic diversity estimates in the northwest and southwest regions, both of which also harbor international cargo ports, than in the southeast region, in which Busan is located. Furthermore, this genetic result was roughly concordant with our questionnaire survey demonstrating that V. velutina was observed in apiaries located in the northwest and southwest regions up to 2012, when there was no reported prevalent distribution of the hornet beyond the southeast region. These results collectively suggest that the northwest and southwest regions of Korea are additional sites of V. velutina entry to the country, independent from the southeast region origin.     

Studies on the characteristics of parasitism ofPlutella xylostella (Lep.: Plutellidae) by a larval parasiteDiadegma semiclausum (Hym.: Ichneumonidae)

Laboratory experiments were conducted to study the characteristics of parasitism of diamondback moth,Plutella xylostella (L.), a worldwide pest of crucifers, by a larval parasite,Diadegma semiclausum Hellén. Results showed that the greater the host larval density, the lesser was the percentage of larvae parasitized. The area of discovery decreased with increasing parasite density, but k-value remained practically unchanged. Parasitism reduced food consumption in parasitised larvae. No difference was observed in duration of larval instars between the parasitized and healthy larvae. As the frequency of superparasitism increased, the proportion of production of female progeny also increased. Presence of parasite larva within the host larva deterred superparasitism greater than the presence of parasite egg. Presence of larva of eitherD. semiclausum or another larval parasite,Cotesia plutellae Kurdjumov, within host larva deterred multiparasitism by either species greater than the presence of egg of either parasite species.Diadegma semiclausum was much more aggressive thanC. plutellae in parasitisingP. xylostella larvae.     

Interspecific discrimination and larval competition amongMicroplitis croceipes,Microplitis demolitor,Cotesia kazak (Hym.: Braconidae), andHyposoter didymator (Hym.: Ichneumonidae), parasitoids ofHeliothis virescens (Lep.: Noctuidae)

Interspecific host discrimination by adults, and larval competition among the endoparasitoidsMicroplitis croceipes (Cresson),Microplitis demolitor Wilkinson,Cotesia kazak (Telenga) andHyposoter didymator (Thunberg) were investigated usingHeliothis virescens (F.) as the host. In ovipositional choice tests, the mean number of encounters and ovipositions for unparasitized hosts was not significantly different from the mean number of encounters and ovipositions for parasitized hosts for each treatment combination (P>0.05). Thus, none of the parasitoid species discriminated between host larvae recently parasitized once by a female of another species und unparasitized hosts. However, in all but two cases, females did discriminate between unparasitized hosts and hosts in which an early first instar of the first-attacking species was developing.Cotesia kazak andH. didymator did not discriminate between unparasitized hosts and hosts parasitized by an early first instar ofM. demolitor. Larval competition among these parasitoid species was studied for three time intervals between the first and second species parasitization: 1) second species attack immediately (5–15 sec) after the first; 2) second species attack 24 h after the first; and 3) second species attack 48 h after the first. Time until egg eclosion was shortest forM. demolitor, thenC. kazak, thenM. croceipes, and longest forH. didymator. When the second parasitoid species attacked a host immediately after the first species, the species in which egg eclosion occurred first was the victor more frequently, except whenM. demolitor competed withC. kazak andH. didymator. With a 24 h delay between the first and second species to attack, the older first instar from the first parasitization usually outcompeted the younger first instar from the second attack. A first instar from the second species to attack generally outcompeted the second instar of the first species when the second parasitization had been delayed 48 h. Competiors were eliminated mainly by physical attack, butC. kazak andM. croceipes apparently also killedH. didymator eggs by physiological processes.     

Both olfactory and visual cues promote the hornet Vespa velutina to locate its honeybee prey Apis cerana

Predators use olfactory, visual and sometimes acoustic cues from the preys to assess food information. However, it is not known if the aggressive hornets (Vespa spp.) use olfactory, visual, or both types of information to find and recognize prey. In the present study, we trained hornet workers (Vespa velutina) to a feeding area. Once the hornets began consistently foraging at this feeding area, we determined whether they located prey (bees, Apis cerana) via olfactory or visual cues. We did this by testing whether hornets were attracted to a dummy bait (bee dummy bait or non-bee dummy bait) treated with extracts of honeybee cuticular hydrocarbons. We then tested whether hornets could distinguish between bee dummy bait and cotton ball dummy bait, both treated with bee odors. Hornets preferred the dummy treated with bee odors, and bee dummies (with bee images) were more attractive to the hornet than the cotton ball dummies with only bee odors. These results clearly indicate that a combination of olfactory and visual cues helps the hornet to locate its prey.     

Differences in the parasitic effects of a bopyrid isopod and rhizocephalan barnacle on the portunid crab,Charybdis bimaculata

Bopyrid isopods and rhizocephalan barnacles are obligate parasite crustaceans which harm their decapod hosts. However, to the best of our knowledge, studies have not compared which of these parasites has a greater parasitic effect on its hosts. Here, the parasitic effect of the bopyrid isopod, Allokepon hendersoni, and an unidentified sacculinid rhizocephalan species, infesting the same population of portunid crabs, Charybdis bimaculata, was investigated and compared for the first time. Samples were collected from the bycatch of a trawl fishery in Tosa Bay, Japan. A total of 2601 crabs were collected, of which 14 (0.55%) were parasitized by the bopyrid and 21 (0.82%) by the rhizocephalan. One of the two female crabs parasitized by the bopyrid was ovigerous (with much fewer eggs than unparasitized females). No ovigerous crab was found from the eight females parasitized by the rhizocephalan. Because only two female crabs were parasitized by the bopyrid, the following analyses were made using the male crabs. Both parasites reduced the wet weight (crab condition) and the cheliped size (secondary growth) of C. bimaculata, but the impact of the parasitism did not differ between the parasite species. The size of the abdominal flap of male hosts was reduced by the bopyrid infestation; however, rhizocephalan infestation caused enlargement of the abdominal flap, which is an indication of feminization. The present study provides information on how the effect of these two parasitic castrators on the same host crab varies. A moderate decrease in crab condition and cheliped development was common among the parasites, suggesting that the degree of impact might be favorable for the survival of the two parasites species.     

The social parasite Phengaris (Maculinea) nausithous affects genetic diversity within Myrmica rubra host ant colonies

Evolutionary theory predicts that high genetic variation maintains plasticity in a species’ response to parasite pressure. However, higher genetic diversity might also cause easier infiltration by social parasites, because odour diversity is high and nest-mate recognition poor. Here we test if the obligate myrmecophile Lycaenid butterfly Phengaris nausithous, a parasite of colonies of the highly polygynous ant Myrmica rubra causes local adaptation by enhancing genetic variance in parasitized versus non parasitized ant populations M. rubra colonies from six infested and three uninfested sites were assayed at five microsatellite loci to quantify genetic variation. Our results reveal isolation by distance and a significantly enhanced intracolonial variance due to the parasite pressure.     

Effects of parasite density and host availability on progeny production byBiosteres (Opius) longicaudatus, [Hym.: Braconidae], a parasite ofAnastrepha suspensa [Dip.: Tephritidae]

Progeny production ofBiosteres (Opius) longicaudatus Ashmead, a larvalpupal parasite of the Caribbean fruit fly,Anastrepha suspensa (Loew) was affected by host availability, previous ovipositional experience, and parasite density and age. Parasitization rates were evaluated in 24.5 cm³ ovipositional cages at parasite densities of 25, 125, and 250 male-female pairs by exposingB. longicaudatus adults to (a) 500A. suspensa larvae for a 24 h period or (b)ad libitum host larvae for each of the 14 days following eclosion. The mean numbers of parasite progeny produced at the 25, 125, and 250 densities were 1076, 1896, and 2038, respectively. The number of progeny produced per surviving female parasite was inversely proportional to the adult parasite density and relatively more female progeny were produced as the adult parasites aged. Host mortality was significantly higher among parasitized larvae. Maximum rearing efficiency was achieved at the 125 density.     

Effects of a parasitic nematode on male mate choice in a livebearing fish with a coercive mating system (western mosquitofish, Gambusia affinis)

I examined the effects of the parasitic larval nematode, Eustrongylides ignotus, on male mate choice in the western mosquitofish, Gambusia affinis. I hypothesized that parasite presence influences male mate choice either directly (via reduction in male mating behavior due to presence of parasite in females) or indirectly (via reduction in male mating behavior due to reduced condition of infected females). Specifically, I tested the predictions that (1) males would mate preferentially with uninfected over infected females (scoring both mating attempts and association time with females); (2) parasitized females would be in poorer condition than non-parasitized females (measured as soluble fat stores); and (3) parasitized females would have reduced fecundity (measured as number of developing embryos). Males preferred to mate with non-parasitized over parasitized females, but showed no differences in association time between females. The nematode did not decrease female body condition, but did decrease female mass, and appeared to decrease female fecundity via reduction in broods (# embryos). Results support that parasites affect male mate choice in mosquitofish; however, the mechanisms used by males to differentiate between parasitized and non-parasitized females remain untested. This study provides the first empirical evidence of parasite affects on male mate choice in livebearing fishes, and suggest a potentially important role for parasite-mediated sexual selection in organisms that use coercive mating as the primary mechanism of obtaining mates.     

Host discrimination byChelonus insularis [Hym.: Braconidae], telenomus heliothidis [Hym.: Scelionidae], andTrichogramma pretiosum [Hym.: Trichogrammatidae]

The ability of female parasitoids (Chelonus insularis Cresson,Telenomus heliothidis Ashmead, andTrichogramma pretiosum Riley) to distinguish between parasitized and unparasitized tobacco budworm,Heliothis virescens (F.), eggs was determined in laboratory studies. All 3 species were relatively efficient at detecting eggs that were previously parasitized by conspecific females.T. heliothidis andT. pretiosum were able to discriminate on the basis of external examination of host eggs, whereasC. insularis appeared to examine hosts internally as well as externally. In interspecific tests, no species readily rejected eggs parasitized by the other 2 species.     

Complete mitochondrial genome of the black‐tailed hornet,Vespa ducalis (Hymenoptera: Vespidae): Genomic comparisons in Vespoidea

We sequenced the complete mitochondrial genome (mitogenome) of the black‐tailed hornet, Vespa ducalis (Hymenoptera: Vespidae). The genome was 15,779‐bp long and contained typical sets of genes [13 protein‐coding genes (PCGs), 22 tRNAs, and 2 rRNAs]. The V. ducalis A + T‐rich region was 166‐bp long and was the shortest of all sequenced Vespoidea genomes, including Vespa. The genome was highly biased toward A/T nucleotides—80.1 % in the whole genome, 77.8 % in PCGs, 83.4–85.6 % in RNAs, and 92.8 % in the A + T‐rich region. These values are well within the typical range for genes and regions of Vespoidea mitogenomes. Start and stop codons in several Vespa species—including V. ducalis—were diversified, despite these species belonging to the same genus. In comparison with the ancestral mitogenomes, Vespa mitogenomes—including that of V. ducalis—showed substantial gene rearrangement; however, we detected no gene rearrangement among Vespa species. We conducted phylogenetic reconstruction based on concatenated sequences of 13 PCGs and two rRNAs (12,755 bp ) in available species of Vespoidea—21 species in six subfamilies in two families (Vespidae and Formicidae). The Bayesian inference and maximum likelihood (ML) methods revealed that each family formed strong monophyletic groups [Bayesian posterior probability (BPP) = 1; ML, 100 %]. Moreover, V. ducalis and V. mandarinia formed a strong sister group (BPP = 1; ML, 94 %).     

The structure and antimicrobial potential of wasp and hornet (Vespidae) mastoparans: A review

Wasp venom is a complex mixture of biologically active components, including high molecular weight proteins, small peptides, bioactive amines, and amino acids. Peptides comprise up to 70% of dried venom. In social wasp venoms, three of the major peptide types are mastoparans, which cause mast cell degranulation, chemotactic peptides, which promote chemotaxis of polymorphonucleated leukocytes, and kinin‐related peptides, which are known to produce pain and increase vascular permeability. Among these, the bioactive tridecapeptide mastoparan is the most common and may even have antimicrobial activity. Herein we summarize the results of studies on vespid mastoparans, focusing on hornets (Vespa spp.) identified following a systematic literature search for mastoparans of hornets in the genus Vespa, the most active mastoparan research taxon. The common features of hornet mastoparans are C‐terminal amidation, amphipathic helical structure, and multiple functions such as mast cell degranulation and hemolysis, as well as membrane permeabilization. Most interestingly, all tested hornet mastoparans have strong antimicrobial activities, suggesting that they can provide useful insights into and opportunities for development of novel antibacterial peptides.     

Parasitism may enhance rather than reduce the predatory impact of an invader

Invasive species can have profound impacts on communities and it is increasingly recognized that such effects may be mediated by parasitism. The ‘enemy release’ hypothesis posits that invaders may be successful and have high impacts owing to escape from parasitism. Alternatively, we hypothesize that parasites may increase host feeding rates and hence parasitized invaders may have increased community impacts. Here, we investigate the influence of parasitism on the predatory impact of the invasive freshwater amphipod Gammarus pulex. Up to 70 per cent of individuals are infected with the acanthocephalan parasite Echinorhynchus truttae, but parasitized individuals were no different in body condition to those unparasitized. Parasitized individuals consumed significantly more prey (Asellus aquaticus; Isopoda) than did unparasitized individuals. Both parasitized and unparasitized individuals displayed Type-II functional responses (FRs), with the FR for parasitized individuals rising more steeply, with a higher asymptote, compared with unparasitized individuals. While the parasite reduced the fitness of individual females, we predict a minor effect on population recruitment because of low parasite prevalence in the peak reproductive period. The parasite thus has a large per capita effect on predatory rate but a low population fitness effect, and thus may enhance rather than reduce the impact of this invader.     

Parasitoeds (Hym.: Aphelinidae) of three scale insects (Hom.: Diaspididae) in a citrus grove in valencia,spain

The parasitoids ofAonidiella aurantii (Maskell),Lepidosaphes beckii (Newman) andParlatoria pergandii Comstock were studied in a Navel orange grove in Valencia, Spain during three years. Four species ofAphytis were identified on yellow sticky traps,Aphytis chrysomphali (Mercet),Aphytis melinus Debach,Aphytis lepidosaphes Compere andAphytis hispanicus (Mercet). No consistent annual pattern was observed in the flight of adults.A. melinus, introduced some years earlier in the grove, was found in very low numbers and showed no signs of increasing and displacingA. chrysomphali as a parasitoid ofA. aurantii. On female scales of the three species sampled at regular intervals from leaves, twigs and fruit, the mean annual rate of active parasitism was similar and ranged from 3.5% to 8%.P. pergandii males were not parasitized, inL. beckii parasitism was usually much lower in male than in female scales, and inA. aurantii it was higher in the males. Scales of the three species were less parasitized on twigs than on leaves, and so wereL. beckii on fruit. The annual trend of parasitism byAphytis on scales fluctuated without a definite pattern. Parasitism byEncarsia inquirenda (Silvestri), an endoparasitoid ofP. pergandii, was more stable throughout the year and increased steadily from year to year.     

Bionomics of Orasema simplex (Hymenoptera: Eucharitidae), a parasitoid of Solenopsis fire ants (Hymenoptera: Formicidae) in Argentina

Biological characteristics of the parasitoid Orasema simplex Heraty (Hymenoptera: Eucharitidae), a potential candidate for the biological control of fire ants in the United States were investigated. Female survivorship, fertility and oviposition preferences were studied in the laboratory. Naturally parasitized colonies were examined to determine offspring sex ratio, development success and time, and to artificially parasitize healthy ant colonies. In addition, field studies were carried out to establish natural oviposition substrates and adult activity patterns. Orasema simplex female survivorship was 3.6 ± 1.5 days. Newly emerged females contained 613.5 ± 114.0 mature eggs. The adult development success in natural parasitized colonies was 22.2% with a female-biased sex ratio (4:1). The time required from planidia to adult was 29.5 ± 5.4 days. In the field, adults were mostly found around the ant nests at midday. A broad range of plant species was observed as oviposition substrates. The transfer of planidia to healthy ant colonies was achieved but the development success was very low. Orasema simplex appears to have a limited potential as a fire ant biocontrol agent because of cosmetic damage to a wide variety of plants used for oviposition. However, further studies are necessary to evaluate the real damage exerted by oviposition punctures.     

Occurrence of Vespa velutina Lepeletier from Korea, and a revised key for Korean Vespa species (Hymenoptera: Vespidae)

This is the first report of occurrence of Vespa velutina Lepeletier from Korea. The diagnosis and taxonomic relationship between geographical subspecies is provided, with a revised key to complement the previous taxonomic information of Korean Vespa species. The ecological aspect of the species is also discussed.     

Species composition,abundance, and annual cycles of fleas (Siphonaptera) on bank voles (Clethrionomys glareolus) in the western part of Vologda Province (Babaevo District)

A total of 383 fleas of 11 species were collected off 428 bank voles (Clethrionomys glareolus) captured near Babaevo (59°4′N, 35°8′E). Three of the species recorded (Amphipsylla rossica, Doratopsylla dasycnema, and Palaeopsylla soricis) were not typical of these rodents, infesting the latter occasionally from other animals, such as the common vole Microtus arvalis and shrews inhabiting adjacent or the same biotopes. Peromyscopsylla bidentata, infesting the bank vole in most part of its range, was recorded only as a single female. Megabothris turbidus was also very rare, being sporadically recorded from May to October; the examined territory probably lies at the northern boundary of its range. The most abundant species, Ctenophthalmus uncinatus, had two peaks of abundance: in April, when adults emerged from overwintered cocoons, and in July. Then their abundance decreased and the last occasional individuals were recorded till December. The year-round parasite Amalaraeus penicilliger was most abundant in winter. Other species were few in number. Adults of Megabothris rectangulatus were recorded from April to August with two peaks of abundance: in April, when they emerged from overwintered cocoons and in July, when the second generation emerged. The univoltine species Peromyscopsylla silvatica emerged in July–August and parasitized till September. Rhadinopsylla integella was the most abundant in October–December, but occasional specimens were recorded in January. The polyxenous species Hystrichopsylla talpae emerged in late July and occurred till September.