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"pronotalis-dealbatus intergrades(?)"

Cicada - Megatibicen pronotalis Cicada - Megatibicen pronotalis Walker's Cicada - Megatibicen pronotalis pronotalis-dealbatus transitionals (?) - Megatibicen pronotalis - male pronotalis-dealbatus transitionals (?) - Megatibicen pronotalis - male
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hemiptera (True Bugs, Cicadas, Hoppers, Aphids and Allies)
Suborder Auchenorrhyncha (Free-living Hemipterans)
Superfamily Cicadoidea (Cicadas, Leafhoppers, and Treehoppers)
Family Cicadidae (Cicadas)
Subfamily Cicadinae
Genus Megatibicen
Species pronotalis (Walker's Cicada)
No Taxon "pronotalis-dealbatus intergrades(?)"
Numbers
There are currently two "poorly defined" subspecies relative to geographic distribution and overlap in characteristics.

Tibicen pronotalis pronotalis
Tibicen pronotalis pronotalis "var. pronotalis" ?
Tibicen pronotalis pronotalis "var. walkeri" ?

Tibicen pronotalis walkeri

Tibicen pronotalis nr. dealbatus (?)
Tibicen dealbatus nr. pronotalis (?)

The sister taxon Tibicen dealbatus (Davis 1915) replaces pronotalis across the western "Great Plains" and is currently recognized as a distinct species. However, these "populations" appear to be closely related and possess similar morphology, calls, calling behaviors and host associations.
Size
Tibicen pronotalis (including both ssp. pronotalis & walkeri) & Tibicen dealbatus are among the largest cicadas in the eastern USA. These taxa are best described as having robust bodies, relatively narrow heads (as compared to the thorax), and are boldly patterned with black, brightly colored with greens, reddish-browns and/or orange and tan (+ heavy white pruinosity in dealbatus).
body length 3 to 4cm
forewing length ~5cm
wingspan 10-13cm
Identification
"Intermediate types (pronotalis - dealbatus transitionals ?)"

The specimens placed here are difficult to assign. Often considered to be "pronotalis" in parts of the range, they are characterized by greater pruinosity - much as seen in dealbatus - and occupy an intermediate range between pronotalis and dealbatus. Given the relationship and similarity, it is likely these represent transitional populations between the two and may deserve a separate guide page. However, for now, I am placing these under pronotalis until additional info becomes available.

1) These populations often possess broader heads than seen in dealbatus (more typical of pronotalis)
2) > pruinosity than seen in pronotalis, often with a well-developed dorsal abdominal mid-line stripe
3) < pruinosity on the thorax and lateral portions of the abdomen than typically seen in dealbatus
3) coloration and pronotal patterns are variable, but often akin to pronotalis in nearby parts of the range (esp. along the Gulf coast of e. Texas).
For additional images of cicadas from this area, please refer to the following site: "Big Thickett Critters"

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PRONOTALIS

T. pronotalis is one of our LOUDEST CALLING EASTERN Tibicen SPECIES.
However, it's not the males' calls that are so ear splitting, but rather the alarm squawks they produce when threatened or picked up! The alarm squawk of a male Tibicen pronotalis (syn. walkeri Metcalf), produces a mean sound pressure level of 105.9 dB(50cm) making it among the loudest insects in the world!
Refer to this link for details Loudest Insects

GENERAL DESCRIPTION: Tibicen pronotalis (syn. walkeri)

1) SIZE: One of our largest eastern species often rivaling T. auletes and T. resonans in size.
[Avg. 2.2-2.7 inches in total length - incl. wings....some specimens may be slightly larger, especially those from the southern part of the range]

2) BODY COLORATION: several color forms can be encountered across the range (referencing "ground coloration")
"Lime-Green": can be widespread - but often more typical of Eastern & Southeastern Populations. Populations in Alabama, Georgia and n. Florida are typically bright lime green with patternless pronota and bright lateral fulvous patches on the mesonota.
"Light Olive/Taupe": widespread but often more common in the western & southwestern reaches of the range - west of the Miss. R.
"Greenish Ochreous-Tan": widespread but often more common in the west central Gulf States (LA & e. TX), western & southwestern reaches of the range - west of the Miss. R.
"Ochreous" or "Yellow-Orange": Seems to occur in the more northern populations, especially those adj. to the Miss. R. and along the periphery of the Plains and Grassland fragments west into the eastern Tall-Grass Prairies ... replaced by dealbatus in the western Prairies
EYE COLORATION: "Light" usu. with a bluish, bluish-grey or purplish cast (rarely the grey-tan or sandy color seen in resh or auletes)

3) PATTERN: The pattern of the mesonotum is relatively consistent in "pronotalis" but may vary some in color and amounts of black (esp. in northern specimens). The lateral fulvous areas are often bright red or brick-colored (occasionally with heavy black). The pronotum may be solid and patternless (typical of southeastern populations) or may exhibit varying degrees of pattern centrally - often intricate (in some extremes, this pattern may be represented by a large centralized black blotch, much as seen in examples of T. cultriformis).

4) VENTER: Lightly Pruinose (usually ochreous with hints of pale green) / No dark pigmentation

5) The dorsum of the abdomen can be described as blackish. In most specimens reviewed, the dorsal aspect of the abdomen is characterized with some slight rust coloration visible on half or more of the dorsal segments.

6) The heavily infuscated (i.e. smoky black-grey) "Z" visible towards the ends of the forewings and typical of most Tibicen species is usually poorly developed to absent in this species with only the cross veins being evident (i.e. The radial and radiomedial cross veins of tegmina, forewing, NOT heavily infuscated or darkened.).

7) The costal margins of the forewings - heavy veins of the leading wing edge - are usually bowed or noticeably arciform (more so than seen in several similar species).

8) MALES: opercula are oblique/rounded & ochreous to olive-yellow colored (rarely orangish-tan)

9) CALL: The call has been described as a deep rhythmic "Yeee-Yeee-Yeee-....." with a subtle underlying rumble ..."broom-broom-broom-...." (difficult to vocally immulate or "spell out"). This species calls from late afternoon 'til well after sunset. The calls of the males are often heard as late as 10 to 11 PM (EDT & CDT).

10) "SUBSPECIES": There are two poorly defined "subspecies". These ssp. or forms are perhaps better described as clinal variants with overlapping coloration & varying degrees of pattern.

Tibicen pronotalis pronotalis (North & West) & Tibicen pronotalis walkeri (South and East)

NOTE: Although some of these variants exhibit phenotypic tendencies with strong geographic affiliations (i.e. clinal), they are not likely representative of "subspecies".
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Distinquishing traits of T. dealbatus are as follows:

1) ABDOMEN: T. dealbatus exhibits greater pruinosity (white powdered wax) than seen in pronotalis. The pruinosity is usually arranged in "dotted stripes" along the sides of the abdomen and dorsal abdominal midline (rare in pronotalis).

2) THORAX: T. dealbatus exhibits greater pruinosity on the thorax (esp. the mesonotum)
Often similar in appearance and confused with "The dorsatus Group"

3) T. dealbatus is usually a bit more compact and has a slightly narrower head than seen in pronotalis

4) COLORATION: Variable in both taxa and not entirely diagnostic!, - tendencies - when T. dealbatus is green, it is typically a duller "pea green" (often more of a ~lime green in pronotalis) - when tan, it is typically more of a sandy-brownish tan as opposed to a ochreous yellow or taupe (green-tan) seen in pronotalis.

5) DISTRIBUTION: Geographic distribution of pronotalis and dealbatus and how they may relate.
To date, neither pronotalis nor dealbatus seem to be sympatric in their "pure" form. Although there is evidence to suggest genetic exchange and blending among adjacent populations (pronotalis x dealbatus), it is unlikely to find both taxa in their "pure forms" coexisting side by side.

6) CALL: The call of dealbatus is identical to that of pronotalis and may be described as a deep rhythmic "Yeee-Yeee-Yeee-....." with a subtle underlying rumble ..."broom-broom-broom-...." (difficult to vocally immulate or "spell out"). This species calls from late afternoon 'til well after sunset. The calls of the males are often heard as late as 10 to 11 PM EDT.

HYPOTHETICAL: Based on call, behaviors, host affinities and morphology, Tibicen dealbatus (Davis 1915), "Plains Cicada" (no accepted common name applies) and Tibicen pronotalis Davis 1938 - [syn. marginalis (Walker 1852)], "Walker's Cicada" are possibly conspecific representing a cline.
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T. resh vs. T. pronotalis

differentiating Tibicen resh from the "T. pronotalis Group"
The "Z" infuscation found near the tip of the forewing is prevalent in resh and NOT so in pronotalis & dealbatus (usu. very faded or absent).

Note the evident "Z" towards the tips of the forewings





(NOTE the faded "Z" - the cross veins are evident but not heavily blackened)


Possible pronotalis-dealbatus transitional (??)
North Dakota


Tibicen pronotalis var. pronotalis
(NOTE the faded "Z" - the cross veins are evident but not heavily blackened)

Tibicen pronotalis var. walkeri
(NOTE the lack of a smoky black "Z" - ONLY the cross veins are evident)

Tibicen pronotalis var. pronotalis
(NOTE the lack of a smoky black "Z" - ONLY the cross veins are evident)
Range
Intermediate specimens between dealbatus and pronotalis occupy an extensive, yet relatively narrow band running from Texas north into the Dakotas.
(TX, OK, KS, NE, SD, & ND)
Habitat
Often riparian
Transitional forests to tall grass prairie

usu. Riparian ecosystems with large quantities of Cottonwoods & Willows (often sycamores + associated Hardwood forests)
Season
For most parts of the range, July-Sept
June-Oct across the Gulf States
Food
This species group (pronotalis, dealbatus & cultriformis) seem to prefer cottonwoods & willow (Salicaceae)
T. pronotalis and allied taxa are also reported from sycamore (Platanaceae)
Less commonly associated with maples and misc. other flood plain hardwoods.
Life Cycle
eggs usually laid in dead twigs, wood or bark
(occasionally eggs may be laid in living stems and twigs)

eggs hatch and nymphs burrow into the soil

nymphs feed on the sap in roots for several years (prefer Pines)

Final instar nymphs emerge and develop into winged adults (emergence for this species usu. occurs at night)
Remarks
1) Songs of pronotalis and dealbatus are identical.

2) Appears to cross with dealbatus - with which it may be conspecific (?).

3) Both pronotalis and dealbatus will call well after sunset (during the day upto ~10:00pm or later), an unusual behavior for most US cicada species.

HYPOTHETICAL: Based on call, behaviors, host affinities and morphology, Tibicen dealbatus (Davis 1915), "Plains Cicada" (no accepted common name applies) and Tibicen pronotalis Davis 1938 - [syn. marginalis (Walker 1852)], "Walker's Cicada" are possibly conspecific and represnt a cline.

4) There are several color forms ranging from bright green to dull straw-yellow + intermediates.

5) There are two poorly defined "subspecies" of pronotlais. These ssp. or forms are perhaps better described as clinal variants with overlapping coloration & varying degrees of pattern.
Tibicen pronotalis pronotalis (North & West) & Tibicen pronotalis walkeri (South and East)
NOTE: The observed differences appear to represent "individual variation". Although some of these variants exhibit phenotypic tendencies with strong geographic affiliations (i.e. clinal), they are not likely representative of "subspecies".