Forum Entomologi Italiani

Altro Gyrinidae fuori misura, stavolta americano:

U.S.A., Michigan, Charlevoix Co., 33°N-5°W, 18.VI.1984, R. Merchant legit
12,5 mm

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Maurizio Gigli
http://utenti.romascuola.net/bups
http://bup.xoom.it/

Altra discussione senza risposte ripescata dalla sezione extrapal.

Almeno al genere credo si possa arrivare.

_________________
Maurizio Gigli
http://utenti.romascuola.net/bups
http://bup.xoom.it/

As far as I know, the genus is Dineutes sp.

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Ciao
Adrian

Grazie Adrian. Seguendo la tua indicazione ho trovato un lavoro, vecchio ma forse ancora utilizzabile, sui Dineutes del Nord America. Si può visualizzare liberamente, ma non scaricare il pdf. Questo è invece disponibile qui, ma compreso nell'intero volume XXII di Transactions of the American Entomological Society.

Ne ho estratto la chiave di identificazione delle specie allora (1890) riconosciute, che è questa:



Sutural angles of elytra rounded in both sexes ... Group A.
Sutural angles of elytra rounded in ♂ , produced and strongly dehiscent in ♀ ... Group B.
Sutural angles of elytra distinct, frequently produced, in both sexes ... Group C.

Group A.
Femora of ♂ not toothed.
- Size large; surface very shining; elytra with a bronze vitta ... vittatus.
Femora of ♂ toothed.
- Size large; opaque, color dark olive; tooth prominent, oblique ... sublineatus.
- Size medium to small; surface black, frequently bronzed.
-- Tooth strong, acute; sutural angles broadly rounded, apices not serrate ... emarginatus.
-- Tooth weak; sutural angles scarcely rounded, apices finely serrulate ... carolinus.


Group B.
Femora of ♂ not toothed.
- Size medium; surface black, not polished, sometimes bronzed.
-- Anterior tibiie gradually broadened from base to apex, tip oblique, exterior angles obtuse. ... hornii.

Group C.
Under surface black, shining, usually bronzed.
- Femora of ♂ not toothed.
-- Size medium, form robust; apices strongly depressed, not dehiscent at suture.
--- Anterior tibiae regularly broadened from base to apex, exterior angle acute, produced ... nigrior.
-- Size medium, form more slender; apices not strongly depressed, dehiscent at suture.
--- Anterior tibiae regularly broadened from base to apex, exterior angle rectangular ... assimilis.
- Femora of ♂ toothed.
-- Size small; apices dehiscent at suture, sutural angles evident, produced.
--- Anterior tibiae cylindrical at basal third, then rather suddenly broadened and continuing nearly parallel to apex, exterior angle acute, produced ... productus.
Under surface brown or testaceous; femora of ♂ toothed.
- Apices of elytra serrulate.
-- Size medium to small; surface very highly polished, not bronzed, strongly narrowed in front; under surface chestnut-brown, serration distinct ... serrulatus.
-- Size medium: surface not highly polished, bronzed, moderately narrowed in front; under surface pitchy-brown, serration fine ... analis.
- Apices of elytra not serrulate.
-- Size moderately large; broad, narrowed in front, surface metallic shining; under surface and legs testaceous to straw color ... discolor.
-- Size small; narrow, very convex, surface polished black; under surface and legs rufous ... angustus.

Copio qui anche le due tavole presenti nel lavoro.






The numbers refer to the same species throughout: a refers to the apices of elytra; b to the genitalia of ♂.
1 - vittatus
2 - sublineatus
3 - emarginatus
4 - carolinus
5 - hornii
6 - nigrior
7 - assimilis (7b - a little distorted by pressure)
8 - productus
9 - serrulatus
10 - analis
11 - discolor
12 - angustus

Con un po' di pazienza penso di poter arrivare alla specie.

_________________
Maurizio Gigli
http://utenti.romascuola.net/bups
http://bup.xoom.it/

In my humble opinion, after a very fugitive sight, it may be productus. But obviously, it need more attention and detailed investigation.

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Ciao
Adrian

A me ha consentito di scaricarlo senza problemi: eccolo qui.

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Marcello Romano

A me no. O meglio, ora si, ma stamattina cliccando su "view PDF" mi diceva che non risultavo una istituzione o un privato autorizzato e non mi mandava avanti. Ora lo apre normalmente! Boh! Meglio così. Avevo intenzione di scaricarmi le singole pagine e ricomporle in un pdf, ma se è già pronto è meglio.

_________________
Maurizio Gigli
http://utenti.romascuola.net/bups
http://bup.xoom.it/