Reduviidae Research Articles

Description of the adult of the thread-legged assassin bug Eugubinus araneus (Hemiptera: Reduviidae) from India, with comments on other congeneric species.

The thread-legged assassin bug Eugubinus araneus Distant, 1903 (Hemiptera: Heteroptera: Reduviidae: Emesinae: Emesini) was described from India on the basis of two nymphs. This paper provides the first description of the adult with illustrations of both the adult and the nymph. A checklist of and a key to species of Eugubinus Distant, 1903, and images of the type material of six additional species of the genus, i.e., E. intrudans Distant, 1915, E. reticolus Distant, 1915, E. canalanus (Distant,1914), E. annulatus (Villiers, 1948), E. forsteri Wygodzinsky, 1953 and E. papuensis Wygodzinsky, 1966, are provided.

Taxonomic review of Xenorhyncocoris Miller (Heteroptera: Reduviidae: Ectrichodiinae), with description of X. attractivus sp. nov. and notes on sexual dimorphism of the genus

The enigmatic millipede assassin bug genus Xenorhyncocoris Miller, 1938 is revised. Previously known species, X. caraboides Miller, 1938, X. princeps Miller, 1949 and X. schoenitzeri Putshkov & Bérenger, 1999, are diagnosed and photographed. A new species, X. attractivus sp. nov., is described based on male and female specimens from northeastern Borneo. The male of Xenorhyncocoris is reported for the first time, revealing the extreme sexual dimorphism present in the genus. The diagnosis of Xenorhyncocoris is extended in order to make it applicable to the new discovery, and a female-based key to species of the genus is updated. Relationships among Xenorhyncocoris and Vilius Stål, 1863, Neozirta Distant, 1919 and Schottus Distant, 1902 are briefly discussed.

Revision and phylogenetic analysis of the genus Acanthischium Amyot & Serville, 1843 (Hemiptera: Reduviidae: Harpactorinae)

Abstract The Neotropical harpactorine assassin bug genus Acanthischium Amyot & Serville, 1843 (Hemiptera: Reduviidae: Harpactorini) includes four valid species: Acanthischium maculatum Amyot & Serville, 1843 (with ten color varieties proposed by Stål [1872]), Acanthischium haglundi Stål, 1866, Acanthischium superbum Haviland, 1931, and Acanthischium invium Elkins, 1961. A taxonomic revision and a morphological phylogenetic analysis were carried out to test species limits and to propose a hypothesis of evolutionary relationships. As a result of the phylogenetic analysis, Acanthischium is characterized on its external morphology by the elongate postocular region, posterior margin of the pronotum with spines, ventral surface of protrochanter with apical and basal protuberances, profemur wider than mesofemur, and protibia strongly curved. After the taxonomic revision we propose nine valid species, taking into consideration characters of external morphology, male and female genitalia, and color patterns: Acanthischium dimidiatum Stål, 1859 stat. rev.; Acanthischium flaviceps Stål, 1872 stat. rev.; Acanthischium haglundi Stål, 1866; Acanthischium kuna sp. nov. from Panama and Colombia; Acanthischium maculatum Amyot & Serville, 1843; Acanthischium meloae sp. nov. from Suriname; Acanthischium nigrum Stål, 1872 stat. rev.; Acanthischium semiflavum Stål,1872 stat. rev.; and Acanthischium superbum Haviland, 1931. We further synonymize A. invium Elkins, 1961 with A. superbum. All but one of the species ‒ A. flaviceps ‒ were included in the phylogenetic analysis, in which Acanthischium was found to be monophyletic, with the following set of relationships: (A. haglundi + (A. nigrum +(A. dimidiatum (A. maculatum, A. semiflavum, A. kuna, A. meloae, A. superbum)))). The resulting phylogenetic pattern indicate a body color transition from drab to more vivid ones, such as orange or red. The species exhibiting red and orange colorations are found in a clade, suggesting an underlying biological phenomenon, such as wasp mimetism.

Carotenoids of hemipteran insects, from the perspective of chemo-systematic and chemical ecological studies

Carotenoids of 47 species of insects belonging to Hemiptera, including 16 species of Sternorrhyncha (aphids and a whitefly), 11 species of Auchenorrhyncha (planthoppers, leafhoppers, and cicadas), and 20 species of Heteroptera (stink bugs, assassin bugs, water striders, water scorpions, water bugs, and backswimmers), were investigated from the viewpoints of chemo-systematic and chemical ecology. In aphids, carotenoids belonging to the torulene biosynthetic pathway such as β-zeacarotene, β,ψ-carotene, and torulene, and carotenoids with a γ-end group such as β,γ-carotene and γ,γ-carotene were identified. Carotenoids belonging the torulene biosynthetic pathway and with a γ-end group were also present in water striders. On the other hand, β-carotene, β-cryptoxanthin, and lutein, which originated from dietary plants, were present in both stink bugs and leafhoppers. Assassin bugs also accumulated carotenoids from dietary insects. Trace amounts of carotenoids were detected in cicadas. Carotenoids of insects belonging to Hemiptera well-reflect their ecological life histories.

Two new species of Abelocephala (Heteroptera: Reduviidae) from Taiwan

The millipede assassin bug genus Abelocephala Maldonado, 1996 (Heteroptera: Reduviidae: Ectrichodiinae: Abelocephalini) is currently comprised of seven Oriental species. Two macropterous males, representing two new species, were recently collected from Taiwan in Malaise trap samples: A. baliensis sp. nov. and A. yilanensis sp. nov. Habitus and structural images are provided for each new species. A revised diagnosis of Abelocephala and an updated identification key to all species of the genus are given.

Rhodnius micki, a new species of Triatominae (Hemiptera, Reduviidae) from Bolivia.

Rhodnius Stål, 1859 is the second largest genus of Triatominae after Triatoma Laporte, 1832, and includes several important Chagas vectors. Genitalia in Reduviidae are frequently used for species identification, but the current use of terminology for it is inconsistent in Triatominae. Here, Rhodnius mickisp. nov., is described from Bolivia and considered as belonging to the pictipes group based on its morphological characters and distribution. Detailed documentation of the genitalia of Rhodnius mickisp. nov. is provided with emphasis on its everted phallus, especially the endosomal sclerites, which are potentially useful as species-level diagnostic features in Rhodnius. To further verify the validity of this species, the head shapes and wing venation patterns of five species in Rhodnius are compared with morphometric analysis. After reviewing taxonomic and comparative morphology papers of assassin bugs, a vocabulary with a terminology of morphological characters, especially of external male genitalic characters, is assembled with the preferred terms and the synonyms listed. Establishing a consistent terminological framework will greatly facilitate future research on the homology of these structures across Triatominae and will ultimately contribute to our understanding of the evolution of these groups.

A new remarkably preserved fossil assassin bug (Insecta, Heteroptera, Reduviidae) from the Eocene Green River Formation of Colorado

AbstractWe describe a new Eocene fossil assassin bug, Aphelicophontes danjuddi gen. et sp. nov. (Reduviidae: Harpactorinae), from the Green River Formation of Colorado. The specimens informing this description are extraordinarily preserved, particularly in the external and internal structures of the adult male genitalia. We discuss implications of the new species for the systematics and evolutionary history of the group, as well as the strength of phylogenetic signal in harpactorine genitalia.

Orientation of Belminus triatomines to cockroaches and cockroaches’ fecal volatiles: an ethological approach

Most triatomine bugs (Hemiptera: Reduviidae: Triatominae) are hematophagous, though Belminus species can live off of cockroach hemolymph to complete their life cycle. In this work, we described the fixed action pattern (FAP) employed by B. ferroae to identify, approach, and suck on a living cockroach. The FAP described here is composed of the following stereotyped behaviors: (1) visual and/or olfactory detection of the cockroach, (2) reaching, (3) cautious approach, (4) antennal exploration, (5) extension of the proboscis, (6) piercing to sedate, (7) walking away and waiting (postsedation behavior), (8) second cautious approach, (9) extension of the proboscis, (10) piercing to suck hemolymph. The FAP sequence observed suggests that Belminus bugs are not predators like the rest of reduviids (assassin bugs)—but are kleptophagous ectoparasites, since they do not attack and kill a prey but rather steal hemolymph from its invertebrate host. Based on these ethological observations, we propose kleptophagy as a trait that naturally groups the Belminus species into the Triatominae subfamily. In order to identify chemicals cues that could elicit such FAP, we examined the behavior of B. corredori, B. ferroae, and B. herreri in response to the cockroaches’ odor, fresh cockroach feces and fresh rodent wastes. The last two sources were tested based on the assumption that abundant chemicals near host refuges could serve as cues for host orientation. We found that the cockroach odor emanating from a box significantly attracted B. corredori and B. herreri in a still air olfactometer. The three Belminus species approached the captive cockroach after 1 h, but avoided to climb the box. Odors emanating from the cockroach feces attracted B. corredori and B. ferroae in a Y-olfactometer. Triatomines and their hosts have intimately shared the same refuge for millions of years; certain molecules occur across invertebrate and vertebrate refuges and are recurrent in human abodes, thus plausibly explaining how these bugs can readily switch to the domestic habitat, while keeping with their kleptophagous nature.

Age-dependent walking and feeding of the assassin bug Amphibolus venator

Abstract Animal behaviours often dependent on age. In many insect species, walking shows an age-dependent decline, and food intake may also be dependent on age. However, few studies have investigated the relationship between age and walking or food intake. In the present study, we compared walking traits and food intake among individuals of different ages in the assassin bug Amphibolus venator (Hemiptera, Reduviidae). The present results showed an age-dependent decline in walking, similar to findings in many animal species. On the other hand, food intake showed a positive correlation with age. Therefore, the decline in walking did not lead to a decline in feeding. The positive relationship between food intake and age may be related to the type of predation, sit-and-wait, used by A. venator via alterations in investment in reproductive traits with age.

Histología del tracto reproductor masculino del chinche depredador <i>Zelus longipes</i> (Heteroptera: Reduviidae)

Reduviidae incluye el mayor número de especies de depredadores terrestres del Orden Hemiptera, incluyendo depredadores de potenciales plagas en los agroecosistemas. A pesar de la gran cantidad de estudios sobre la taxonomía y morfología del grupo, su filogenia y estrategias reproductivas aún no han sido totalmente dilucidadas. En este trabajo, la histología del tracto reproductivo masculino de Zelus longipes fue descrita con el objetivo de incrementar las fuentes de caracteres para estudios de biología reproductiva del grupo. Para esto fueron utilizadas técnicas de microscopia de luz. Los machos adultos fueron recolectados directamente en un cultivo de maíz, en el municipio de Rio Paranaíba, Minas Gerais. El sistema reproductor está compuesto por dos testículos, cada uno con siete folículos con quistes en diferentes fases del espermatogénesis, vasos deferentes, vesículas seminales, glándulas accesorias pareadas y lobadas en un ducto eyaculatorio. Cuando los espermatozoides están maduros salen de los testículos agrupados en haces y quedan almacenados en las vesículas seminales. Las glándulas accesorias producen diferentes tipos de secreciones que se unen al esperma para formar el semen. Los conductos deferentes fluyen hacia un solo conducto eyaculador.

Crouching Tiger, Hidden Protein: Searching for Insecticidal Toxins in Venom of the Red Tiger Assassin Bug (Havinthus rufovarius).

Assassin bugs are venomous insects that prey on other arthropods. Their venom has lethal, paralytic, and liquifying effects when injected into prey, but the toxins responsible for these effects are unknown. To identify bioactive assassin bug toxins, venom was harvested from the red tiger assassin bug (Havinthus rufovarius), an Australian species whose venom has not previously been characterised. The venom was fractionated using reversed-phase high-performance liquid chromatography, and four fractions were found to cause paralysis and death when injected into sheep blowflies (Lucilia cuprina). The amino acid sequences of the major proteins in two of these fractions were elucidated by comparing liquid chromatography/tandem mass spectrometry data with a translated venom-gland transcriptome. The most abundant components were identified as a solitary 12.8 kDa CUB (complement C1r/C1s, Uegf, Bmp1) domain protein and a 9.5 kDa cystatin. CUB domains are present in multidomain proteins with diverse functions, including insect proteases. Although solitary CUB domain proteins have been reported to exist in other heteropteran venoms, such as that of the bee killer assassin bug Pristhesancus plagipennis, their function is unknown, and they have not previously been reported as lethal or paralysis-inducing. Cystatins occur in the venoms of spiders and snakes, but again with an unknown function. Reduction and alkylation experiments revealed that the H. rufovarius venom cystatin featured five cysteine residues, one of which featured a free sulfhydryl group. These data suggest that solitary CUB domain proteins and/or cystatins may contribute to the insecticidal activity of assassin bug venom.

<p><strong>Rescuing a lost damsel: a revised identity for the extinct true bug <em>Miocoris fagi </em>(Heteroptera)</strong></p>

The fossil heteropteran Miocoris fagi Cockerell, 1927 stat. rev. is redescribed and transferred from Reduviidae to the nominate tribe in Nabidae. The fossil Nabidae are surveyed and enumerated. One taxon, Sinanabis brevipes Zhang, 1986 stat. rev., is removed from Nabidae and is considered incertae familiae.

Climate change has different predicted effects on the range shifts of two hybridizing ambush bug (Phymata, Family Reduviidae, Order Hemiptera) species.

AimA universal attribute of species is that their distributions are limited by numerous factors that may be difficult to quantify. Furthermore, climate change‐induced range shifts have been reported in many taxa, and understanding the implications of these shifts remains a priority and a challenge. Here, we use Maxent to predict current suitable habitat and to project future distributions of two closely related, parapatrically distributed Phymata species in light of anthropogenic climate change.LocationNorth America.Taxon Phymata americana Melin 1930 and Phymata pennsylvanica Handlirsch 1897, Family: Reduviidae, Order: Hemiptera.MethodsWe used the maximum entropy modeling software Maxent to identify environmental variables maintaining the distribution of two Phymata species, Phymata americana and Phymata pennsylvanica. Species occurrence data were collected from museum databases, and environmental data were collected from WorldClim. Once we gathered distribution maps for both species, we created binary suitability maps of current distributions. To predict future distributions in 2050 and 2070, the same environmental variables were used, this time under four different representative concentration pathways: RCP2.6, RCP4.5, RCP6.0, and RCP8.5; as well, binary suitability maps of future distributions were also created. To visualize potential future hybridization, the degree of overlap between the two Phymata species was calculated.ResultsThe strongest predictor to P. americana ranges was the mean temperature of the warmest quarter, while precipitation of the driest month and mean temperature of the warmest quarter were strong predictors of P. pennsylvanica ranges. Future ranges for P. americana are predicted to increase northwestward at higher CO2 concentrations. Suitable ranges for P. pennsylvanica are predicted to decrease with slight fluctuations around range edges. There is an increase in overlapping ranges of the two species in all future predictions.Main conclusionsThese evidences for different environmental requirements for P. americana and P. pennsylvanica account for their distinct ranges. Because these species are ecologically similar and can hybridize, climate change has potentially important eco‐evolutionary ramifications. Overall, our results are consistent with effects of climate change that are highly variable across species, geographic regions, and over time.

Intake of Plant Resin Through the Genitalia of Two Asian Assassin Bugs (Reduviidae: Harpactorinae: Harpactorini)

Many insects use tactics to protect their eggs from predation, infection, and water loss, among other risks. Some assassin bugs only in the New World tribe Apiomerini are known to use plant substances, such as resin, instead of secretions to protect their eggs. Here, we report a novel storage mechanism and the utilization of plant resin for egg protection in Asian assassin bugs, Velinus nodipes and Agriosphodrus dohrni (tribe: Harpactorini). Adult females of both species were observed to take in plant resin through their genitalia. We reported on the handling of resin by these species and confirmed that A. dohrni adult females stored resin in their subrectal glands and that the substance covering their egg masses was derived from plant resin. This is the first report on the storage of plant resin inside the bodies of assassin bugs and on resin-protected eggs in Harpactorini. Such internal resin storage was not accompanied by external morphological features, as observed in some Apiomerini assassin bugs, thereby suggesting that this tactic has been overlooked and may have evolved in broader tribes of assassin bugs than previously thought.

Anthelminthic Activity of Assassin Bug Venom against the Blood Fluke Schistosoma mansoni.

Helminths such as the blood fluke Schistosoma mansoni represent a major global health challenge due to limited availability of drugs. Most anthelminthic drug candidates are derived from plants, whereas insect-derived compounds have received little attention. This includes venom from assassin bugs, which contains numerous bioactive compounds. Here, we investigated whether venom from the European predatory assassin bug Rhynocoris iracundus has antischistosomal activity. Venom concentrations of 10–50 µg/mL inhibited the motility and pairing of S. mansoni adult worms in vitro and their capacity to produce eggs. We used EdU-proliferation assays to measure the effect of venom against parasite stem cells, which are essential for survival and reproduction. We found that venom depleted proliferating stem cells in different tissues of the male parasite, including neoblasts in the parenchyma and gonadal stem cells. Certain insect venoms are known to lyse eukaryotic cells, thus limiting their therapeutic potential. We therefore carried out hemolytic activity assays using porcine red blood cells, revealing that the venom had no significant effect at a concentration of 43 µg/mL. The observed anthelminthic activity and absence of hemolytic side effects suggest that the components of R. iracundus venom should be investigated in more detail as potential antischistosomal leads.

Revision of the assassin bug genus Neopirates (Heteroptera: Reduviidae: Peiratinae), with descriptions of two new species from Namibia

The African assassin bug genus Neopirates Miller, 1952, is revised. The type species, N. nyassae Miller, 1952, is redescribed and illustrated; two new species from Namibia, N. bicolor Liu & Cai sp. n. and N. xanthothorax Liu & Cai sp. n. are described and a key is provided to separate the three species of this genus. Sphodrembas fumipennis Swanson, 2019, the type species of Sphodrembas Swanson, 2019, is placed as a junior synonym of N. nyassae, resulting in Sphodrembas becoming a junior synonym of Neopirates. Morphological differences between Neopirates and similar genera and the distribution of Neopirates are briefly discussed.

The Glycan Structure of T. cruzi mucins Depends on the Host. Insights on the Chameleonic Galactose.

Trypanosoma cruzi, the protozoa that causes Chagas disease in humans, is transmitted by insects from the Reduviidae family. The parasite has developed the ability to change the structure of the surface molecules, depending on the host. Among them, the mucins are the most abundant glycoproteins. Structural studies have focused on the epimastigotes and metacyclic trypomastigotes that colonize the insect, and on the mammal trypomastigotes. The carbohydrate in the mucins fulfills crucial functions, the most important of which being the accepting of sialic acid from the host, a process catalyzed by the unique parasite trans-sialidase. The sialylation of the parasite influences the immune response on infection. The O-linked sugars have characteristics that differentiate them from human mucins. One of them is the linkage to the polypeptide chain by the hexosamine, GlcNAc, instead of GalNAc. The main monosaccharide in the mucins oligosaccharides is galactose, and this may be present in three configurations. Whereas β-d-galactopyranose (β-Galp) was found in the insect and the human stages of Trypanosoma cruzi, β-d-galactofuranose (β-Galf) is present only in the mucins of some strains of epimastigotes and α-d-galactopyranose (α-Galp) characterizes the mucins of the bloodstream trypomastigotes. The two last configurations confer high antigenic properties. In this review we discuss the different structures found and we pose the questions that still need investigation on the exchange of the configurations of galactose.

Evolution of wing polymorphism and genital asymmetry in the thread‐legged bugs of the tribe Metapterini Stål (Hemiptera, Reduviidae, Emesinae) based on morphological characters

AbstractWing polymorphism and asymmetric male genitalia are intriguing morphological phenomena occurring in insects. Among Emesinae, or thread‐legged bugs, the tribe Metapterini Stål exhibits these two interesting morphological attributes. Nonetheless, evolutionary interpretations of these phenomena cannot be put forward because phylogenetic hypotheses for Emesinae are lacking. Thread‐legged bugs are easily recognized among assassin bugs due to their elongated and seemingly delicate body. The tribe Metapterini has 28 genera and approximately 280 described species. The only available phylogenetic hypothesis among Emesinae tribes was proposed by Wygodzinsky (1966), and it hypothesized Deliastini Villiers as the sister group of Metapterini, although this hypothesis has never been tested with cladistic approaches. Recent analyses using character sets of genitalia and prolegs suggest that Metapterini might not be monophyletic. In order to test these ideas, we compiled a morphological dataset of 138 characters that includes external morphological characters, detailed features of prolegs and genitalia of both sexes for Metapterini, which were analysed cladistically including 55 terminals, comprising 24 genera (85.7% of the generic diversity), 43 species of Metapterini and 12 outgroups. Metapterini was recovered as paraphyletic by the inclusion of Bergemesa Wygodzinsky, Palacus Dohrn and Stalemesa Wygodzinsky, all currently assigned to Deliastini. Gardena Dohrn (Emesini) was recovered as the sister group of Metapterini + Deliastini as suggested by Wygodzinsky (1966). Based on these results, we synonymize Deliastini syn. n. with Metapterini sensu n. and propose two new genera: Bacata Castro‐Huertas & Forero gen. n., for three Andean species previously placed in Liaghinella Wygodzinsky, and Valkyriella Castro‐Huertas & Forero gen. n. for Ghilianella borgmeieri Wygodzinsky. Ancestral state reconstruction of wing polymorphism indicates that males and females were fully winged in the ancestor of Metapterini sensu n. with two independent evolutionary transitions to the apterous and brachypterous conditions. The analysis of the symmetry of the male genitalia shows an ancestor with symmetric male genitalia and two independent emergences of asymmetrical male genitalia in Metapterini.

Redescription of the African assassin bug Ectomocoris proximus (Hemiptera: Heteroptera: Reduviidae) with a new synonymy.

The African peiratine assassin bug species, Ectomocoris proximus Miller, 1952 (Hemiptera: Heteroptera: Reduviidae) is redescribed and E. limbatus Miller, 1952, syn. nov., is placed as its junior synonym. Types of both nominal species were examined, habitus images and figures of the male genitalia are provided.

Context-dependent venom deployment and protein composition in two assassin bugs.

The Heteroptera are a diverse suborder of phytophagous, hematophagous, and zoophagous insects. The shift to zoophagy can be traced back to the transformation of salivary glands into venom glands, but the venom is used not only to kill and digest invertebrate prey but also as a defense strategy, mainly against vertebrates. In this study, we used an integrated transcriptomics and proteomics approach to compare the composition of venoms from the anterior main gland (AMG) and posterior main gland (PMG) of the reduviid bugs Platymeris biguttatus L. and Psytalla horrida Stål. In both species, the AMG and PMG secreted distinct protein mixtures with few interspecific differences. PMG venom consisted mostly of S1 proteases, redulysins, Ptu1‐like peptides, and uncharacterized proteins, whereas AMG venom contained hemolysins and cystatins. There was a remarkable difference in biological activity between the AMG and PMG venoms, with only PMG venom conferring digestive, neurotoxic, hemolytic, antibacterial, and cytotoxic effects. Proteomic analysis of venom samples revealed the context‐dependent use of AMG and PMG venom. Although both species secreted PMG venom alone to overwhelm their prey and facilitate digestion, the deployment of defensive venom was species‐dependent. P. biguttatus almost exclusively used PMG venom for defense, whereas P. horrida secreted PMG venom in response to mild harassment but AMG venom in response to more intense harassment. This intriguing context‐dependent use of defensive venom indicates that future research should focus on species‐dependent differences in venom composition and defense strategies among predatory Heteroptera.