Sphecius grandis

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Sphecius grandis
Sphecius grandis in mating, in Big Bend National Park, Texas

Sphecius grandis in mating, in Big Bend National Park , Texas

Systematics
Subordination : Waist Wasps (Apocrita)
without rank: Digger wasps (Spheciformes)
Family : Crabronidae
Subfamily : Bembicinae
Genre : Sphecius
Type : Sphecius grandis
Scientific name
Sphecius grandis
( Say , 1823)

Sphecius grandis (colloquially English Western Cicada Killer ) is a digger wasp species from the genus Sphecius in the family of Crabronidae . The species occurs in the western part of the United States , in Central America and Mexico , its range is west of the closely related species Sphecius speciosus (" Eastern Cicada Killer ") in the eastern United States.

The species supplies its nest with singing cicadas . The females catch around four cicadas as a reserve and store them in the brood cells, from which the larva feeds. The wasps are usually not aggressive towards humans.

Sphecius grandis can be distinguished from Sphecius convallis ( Pacific Cicada Killer Wasp ), with whom it often occurs together, mostly by the color pattern of the tergites of the free abdomen (gaster). However, a more recent study shows that a determination is only uncertain based on this characteristic. For a safe address, the density of the punctures on the tergites of the first two free abdomen segments must also be used.

features

The animals reach a body length between 3 and 5 cm. They are predominantly brown-red to almost black in color, with a variable yellow pattern of spots mostly on the first five abdominal stereotypes, but occasionally only on the first three or four, or also on the sixth. The first and second tergites of the Gaster always also have brown-red spots. The males are moreover distinguishable from all other species of the genus by the shape of the antennae; these are widened on the underside and thus noticeably curved. The average wing length of the females is between 2.5 and 3 cm. Females are larger than males, the sexes can be distinguished, as is typical for the relationship, by the number of whiplash members of the antennae (ten in the female, eleven in the male). In addition, females carry two greatly enlarged flattened spurs on the rails of the hind legs, which they use to dig the nest. The males usually die within a few days of fertilizing the females. The males reach an average weight of 95  mg while the females reach up to 256 mg,

Differentiation from the other species of the genus

The distinction between S. grandis and the other four American species of the genus Sphecius ( S. convallis , S. hogardii , S. speciosus , S. spectabilis ) is not easy. In the west of North America there are only two species whose range overlaps here. In these, the females of S. convallis differ from the females of S. grandis mostly by the yellow markings only on the first to the third tergite of the Gaster. However, this distinction turns out to be uncertain, as there are great individual differences within the species.

Charles W. Holliday and Joseph R. Coelho released a new key in 2004 to differentiate the Sphecius species: After examining 4,451 wasps, they found that 98% of female S. convallis had a yellow mark on tergites one to four (or less), in S. grandis 98% of the females had a yellow mark on the tergites one to five (or more). The 2% of the S. grandis females, in which the number of tergites marked in yellow was no different to S. convallis , could be distinguished by the density of the puncturing of the first versus the second tergum.

Biology and way of life

food

Like all other American species of the genus, S. grandis only hunts singing cicadas for their offspring.

The females hunt the cicadas, which are mostly sitting on tree trunks, and sometimes orient themselves to the song of the male cicadas. The victims are stunned by the wasp venom. The females drag the cicadas into the nest and place several of them in the brood tubes, where they lay an egg in each brood tube. The prey can be up to 88% heavier than the females. Depending on the size of the cicadas, each brood cell is provided with one to three cicadas. Each female manages to bring in a limited number of cicadas during her life, at most eight; this severely limits the number of offspring per female. When the larvae hatch, they feed on the anesthetized cicadas.

Two singing cicada species of the genus Diceroprocta , a Pacarina and three Tibicen species have been identified as prey for Sphecius grandis . For Tibicen dealbatus , only one observation of a prey-carrying female is available. Two species were recorded as prey on a more closely examined area in Arizona, Tibicen duryi and Tibicen parallelus , with males being slightly preferred to females (55 percent), which is in contrast to other species in the genus that preferred females as prey. Three other species of singing cicada that were active when the digger wasp was active were ignored.

Life cycle, mating and territorial behavior

The nesting behavior is the same as with S. speciosus . All Sphecius species build their nests in the ground and the nest clusters can contain several hundred nests, each of which is filled by a female. The tunnels are usually laid in well-drained, sandy soil, often under beaten paths, mostly in the blazing sun. The nests are only rarely created in overgrown areas. The burrows can easily be recognized by the U-shaped "collar" made of excavated material around the entrance hole.

After the larvae hatch from the egg, they feed on the supply of paralyzed cicadas that the females have dragged into the nests. After pupation the new hatch imagines in the summer, from July to early August, the following year. The hatching time of the females coincides with the appearance of the species of cicada in the area ( Tibicen duryi , T. parallelus ), which hunt the wasps.

Sphecius speciosus has many similarities with Sphecius grandis .

The males hatching a little earlier occupy territories in the areas where the young females hatch from the previous year's ground nests. After leaving the nest, the females are ready to conceive immediately, but do not choose their partner, but rather mate with the first male they find, usually a territory owner. After this mating they repel all further attempts at mating. In territorial fights, the males are brutal and do not shy away from damaging the wings or limbs of rivals. The average lifespan of an individual male is only 12 days. In general, the larger males are also the stronger and therefore more dominant. Smaller males, who have little chance in turf wars, try alternative strategies to achieve success. Either they evade in times when fewer animals are hatching and thus the competition is lower, or they do not occupy any territory and try to be successful like a raid when the territory owner is absent or distracted.

Males look for seats near the nests and guard the surrounding territory. They are always in a vigilant position to fend off other males. A study by a behavioral ecologist , John Alcock , showed that the majority of tagged wasps return to the same hide on a daily basis and only two males alternated between two different locations. The animals rarely sit on the ground.

Thermoregulation

S. grandis have the ability to thermoregulate , which means they are able to hunt during the day despite the high daytime temperatures. A study by Joseph Coelho showed that the animals maintained a high but regulated chest temperature during patrol flights. Experiments showed that the wasps have the ability to conduct heat from the thorax to the abdomen and that the abdomen generally stays cooler than the thorax. Dead wasps that were placed in the sun, on the other hand, reached unusually high temperatures in relation to their surroundings.

distribution

The species is distributed in the Nearctic and Neotropical zones from Central America to the western United States. In the US, there is reliable evidence for all states west of the continental divide , with the exception of Wyoming, and it is common in the western Midwest and the southwest, in New Mexico and in western Texas. The northern limit of the distribution is in central Washington.

Sphecius grandis live sympatric with S. convallis and, in a narrow strip in the middle of the continent, with S. speciosus (from southeastern Arizona and Colorado via New Mexico, Texas, Oklahoma and Kansas, to Chihuahua, Coahuila, Nuevo Leon and the North of Tamaulipas in Mexico). Although the species, like its relatives, avoids the higher mountain ranges, it occurs in higher altitudes than the sympatric S. convallis . A study showed that S. grandis occurs on average at altitudes of 755 m ± 23.3 m, while the average for S. speciosus is 219 m ± 4.7 m, for S. convallis it is 582 m ± 30.9 m and for S. hogardii at 18 ± 5 m. S. grandis often occurs in riparian zones. In Mexico it was found in Baja California Norte , Baja California Sur , Coahuila , Nuevo León , Tamaulipas and Yucatán, and in Nicaragua in Granada , in Costa Rica in Guanacaste and in Honduras .

Contact with people

The species is mostly harmless to humans. The poison is not very dangerous compared to other large hymenoptera species. In the test on mice, the fatal (lethal) dose was 46 milligrams of venom per kilogram of body weight, making it far more than ten times more harmless than honey bee venom. The pain response according to the Schmidt Sting Pain Index was 1–2, also lower than a bee sting.

The wasps often interact with humans as they often make their nests in backyards, gardens, and sidewalks. Control is usually unnecessary as the females are not aggressive. However, they sting when caught or kicked. The stings were described as being rather mild. Males are territorial and sometimes fly very aggressively at people as “intruders” into their territory, but, like all hymenoptera males, cannot sting.

Systematics

Specius grandis was first described by Thomas Say in 1824 using specimens from Madera Canyon , Arizona . He named the species Stizus grandis . The new combination in the genus Sphecius Dahlbom in 1843 was carried out by Anton Handlirsch in 1889. The scientific name grandis means "large". It is one of five Sphecius species in America, including four in North America. The genus Sphecius comprises at least 21 species worldwide.

Recently, speculations have been published that the Western Cicada killers actually belong to two cryptic species. Analysis of mitochondrial DNA from specimens in a study in Big Bend National Park , Texas , showed that the Western Cicada killers are genetically split into two clades , possibly representing two different species. The two clades appear to be separated by the Rocky Mountains , with one mainly found in the south and east and the other in the west. They occur there together with the Eastern Cicada killer ( S. speciosus ) and the Pacific cicada killer ( S. convallis ) in the same biotopes and also hunt the same species of cicada.

literature

Individual evidence

  1. ↑ a b c d Charles W. Holliday; Joseph R. Coelho: Improved Key to New World Species of Sphecius (Hymenoptera: Crabronidae). In: Annals of the Entomological Society of America. 99 (5), 2006: 793-798 doi : 10.1603 / 0013-8746 (2006) 99 [793: IKTNWS] 2.0.CO; 2
  2. ↑ a b c d e f Jon Hastings: Provisioning by female Western cicada killer wasps, Sphecius grandis (Hymnoptera: Sphecidae): influence of body size and emergence time on individual provisioning success. In: Journal of the Kansas Entomological Society , vol. 59, April 2, 1986: 262-268. JSTOR 25084766
  3. ^ Joseph R. Coelho: Sexual size dimorphism and flight behavior in cicada killers. In: Oikos 79 (2), 1997: 371-375 doi: 10.2307 / 3546021 JSTOR 3546021 .
  4. ↑ a b c d e f Lee Townsend: Cicada Killer Wasps. University of Kentucky 2010.
  5. ↑ a b c d Zachary Zolinas: A Dynamic Balance Living in the Sonoran Desert. In: Juntos , Unit Two 1999: 12.
  6. ↑ a b Jon Hastings: Sexual-size dimorphism in Western cicada killer wasps, Sphecius grandis (Hymenoptera: Sphecidae). In: Transactions of the Kentucky Academy of Science. vol. 50, 1-2: 1-5.
  7. ^ A b Charles W. Holliday, Jon M. Hastings, Joseph R. Coelho: Cicada prey of New World cicada killers, Sphecius spp. (Dahlbom, 1843) (Hymenoptera: Crabronidae) In: Entomological News. 120 (1), 2009: 1-17. doi: 10.3157 / 021.120.0101
  8. ^ A b Ensign Howard Evans, Kevin M. O'Neill: The Sand Wasps: Natural History and Behavior. Harvard University Press 2007. ISBN 0-674-02462-1 , at page 34.
  9. ↑ a b Jon M. Hastings; Patrick J. Schultheis; Maggie Whitson; Charles W. Holliday; Joseph R. Coelho; Angela M. Mendell: DNA barcoding of new world cicada killers (Hymenoptera: Crabronidae). In: Zootaxa vol. 1713: 27-38, 2008. hdl = 10385/598
  10. ^ A b Jon Hastings: Protandry in western cicada killer wasps ('Sphecius grandis', Hymnoptera: Sphecidae) and empirical study of emergence time and mating opportunity. In: Behavioral Ecology and Sociobiology. April 1989 vol. 25, 4: 255-260. doi: 10.1007 / BF00300051 JSTOR 4600338
  11. ^ Ensign Howard Evans, Kevin M. O'Neill: The Sand Wasps: Natural History and Behavior. Harvard University Press 2007. ISBN 0-674-02462-1 , at page 35.
  12. ^ Jon M. Hastings: The Influence of Size, Age and Residency Status in Territory Defense in Male Western Cicada Killer Wasps ("Sphecius grandis", Hymenoptera: Sphecidae) In: Journal of the Kansas Entomological Society. vol. 62, 3, Jul 1989: 363-373
  13. ^ John Alcock: The behavior of western cicada killer males, Sphecius grandis (Sphecidae, Hymenoptera). In: Journal of Natural History vol. 9, 5, 1975: 561-566. doi: 10.1080 / 00222937500770431
  14. ↑ a b Joseph R. Coelho, Charles W. Holliday, Jon. M. Hastings, Elizabeth Maty, Meghan Swigart, Angela Mendel: Thermoregulation in male western cicada killers ( Sphecius grandis Say) in the Chihuahuan desert. In: Journal of Thermal Biology. July 2007 vol. 32, 5: 270-275 doi: 10.1016 / j.jtherbio.2007.01.016 .
  15. ^ A b c Joseph R. Coelho, Charles W. Holliday, Jon M. Hastings: The Geographic Distributions of Cicada Killers ( Sphecius ; Hymenoptera, Crabronidae) in the America. In: The Open Entomology Journal. vol. 5, March 2011: 31-38. Download PDF
  16. ^ Vincent H. Resh, Ring T. Cardé (Editors): Encyclopedia of Insects. Academic Press (Elsevier), San Diego, USA 2003. ISBN 0-12-586990-8 . in the chapter Venom, on page 1162.
  17. ↑ Kathryn Gardner: Stinging Insects: Cicada Killer Wasps. ( Memento of the original from March 6, 2005 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Masterbeekeeper.org, Dyce Laboratory for Honey Bee Studies, July 2004. @1@ 2Template: Webachiv / IABot / www.masterbeekeeper.org
  18. ↑ Edward Bechinsky, Frank Merickel: Homeowner Guide to Minor Stinging Insects. PDF University of Idaho , May 2009: 7 pages.
  19. ↑ Jorge Víctor: Sphecidae y Crabronidae (Hymenoptera) - De algunos Municipios del Centro y Sur de Tamaulipas, México. ( Memento of the original from September 25, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Acta Zoológica Mexicana. vol. 23, 3, 2007: 35-48. @1@ 2Template: Webachiv / IABot / redalyc.uaemex.mx
  20. ↑ Sphecius . in Catalog of Sphecidae, compiled by Wojciech J. Pulawski. California Academy of Science. last updated: 23 September 2017.

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