Reduviidae (from the contained genus, Reduvius which comes from the Latin reduvia meaning hangnail or remnant) is a large, cosmopolitan family of predatory insects in the suborder Heteroptera. It includes assassin bugs (genera include Melanolestes, Platymeris, Pselliopus, Rasahus, Reduvius, Rhiginia, Sinea, Triatoma, and Zelus), wheel bugs (Arilus cristatus), and thread-legged bugs (the subfamily Emesinae, including the genus Emesaya). There are about 7000 species altogether, making it one of the largest families in the Hemiptera.

Physical characteristics

A Zelus genus nymph from the Southeastern United States.

Adult insects often range from 4 to 40 mm. They most commonly have an elongated head with a distinct narrowed neck, long legs, and a prominent, segmented tube for feeding (rostrum). Most species are dark in color with hues of brown, black, red, or orange. The most distinctive feature of the family is that the tip of the rostrum fits into a groove in the prosternum, where it is rasped against ridges there (a stridulitrum) to produce sound, a tactic often used to intimidate predators. If harassment continues, they can use their rostrum to deliver a painful bite which in some species can be medically significant. The saliva of the reduviid species Rhynocoris marginatus (Fab.) and Catamirus brevipennis (Servile) have anti-bacterial activity towards the human pathogens Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhimurium and one Gram-positive Streptococcus pyogenes.

Feeding

Assassin Bug (Gminatus australis) feeding on a beetle

They use the long rostrum to inject a lethal saliva that liquefies the insides of the prey, which are then sucked out. The saliva is generally made up of proteinaceous materials and digestive enzymes which are used to predigest (generally referred to as Extra-Oral Digestion - EOD).^[1] The legs of some of these bugs are covered in tiny hairs that serve to make them sticky to hold onto their prey while they feed. The saliva is commonly effective at killing substantially larger prey than the bug itself. As nymphs, some species will cover and camouflage themselves with debris, or the remains of dead prey insects. In southern part of the Tamil Nadu, India a reduviid species named as (Acanthaspis pedestris) nymphal instars camouflage. Some species have been known to feed on cockroaches or bedbugs (in the case of the masked hunter) and are regarded in many locations as beneficial. Some people breed them as pets and for insect control. The saliva of reduviid Rhynocoris marginatus showed some insecticidal activity (in vitro) towards the lepidopteran pest further the saliva reduced food consumption, assimilation and utilization efficiency of the pest. With additionally the anti-aggregation factors of saliva alters prey haemocytes aggregation and spreading^[2]

Some assassin bug groups specialize on certain prey groups, such as ants (feather-legged bugs - Holoptilinae), termites, or diplopods (Ectrichodiinae).

Some blood-sucking species, particularly Triatoma spp. and other members of the subfamily Triatominae (e.g., Paratriatoma hirsuta), are also known as kissing bugs due to their habit of biting humans in their sleep on the soft tissue of the lips and eyes; a number of these haematophagous species, located in Central and South America, are able to transmit a potentially fatal trypanosome disease known as Chagas disease (American trypanosomiasis).

Rhinocoris - Predacious Flower assassin bug from South Africa. May bite when carelessly handled; painful after-effects may persist for months.^[3]

Phylogeny

Current taxonomy is based on morphological characteristics. The first cladistic analysis based on molecular data (mitochondrial and nuclear ribosomal DNA) was published in 2009 and called into question the monophyly of some current groups, such as the Emesinae.^[4]

References

1. ^ Sahayaraj, Kitherin; Ayyachamy Vinoth Kanna and Subramanian Muthu Kumar (2010). [=176 "Gross Morphology of Feeding Canal, Salivary Apparatus and Digestive Enzymes of Salivary Gland of Catamirus brevipennis (Servile) (Hemiptera: Reduviidae)"]. Journal of the Entomological Research Society 12 (2): 37–50. http://www.entomol.org/journal/index.php?journal=JERS&page=article&op=view&path[]=176. 
2. ^ Kitherin, Sahayaraj; S. Muthukumar (2011). "Zootoxic effects of reduviid Rhynocoris marginatus (Fab.) (Hemiptera: Reduviidae) venomous saliva on Spodoptera litura (Fab.)". Toxicon 58 (5): 415–425. http://www.sciencedirect.com/science/article/pii/S0041010111001887. 
3. ^ Alan Weaving; Mike Picker; Griffiths, Charles Llewellyn (2003). Field Guide to Insects of South Africa. New Holland Publishers, Ltd. ISBN 1-86872-713-0. 
4. ^ *Weirauch, Christiane & Munro, James B. 2009. Molecular phylogeny of the assassin bugs (Hemiptera: Reduviidae), based on mitochondrial and nuclear ribosomal genes. Molecular Phylogenetics and Evolution: 53 (2009) 287–299