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Identification characters
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Category :: Identification characters
The distinctive front tarsi of the male of Platycheirus clypeatus. Note the markings on the basal segment - clearest on the left - with a vertical white streak with a black spot near the apex of the tarsus.
The male genital capsule of Sphaerophoria scripta
Melanostoma scalare (left) and M. mellinum (right) - compare the size of the dust spots on just behind the antennae
Only a few genera of the Syrphini have yellow stripes along the sides of the thoraz - (Chrysotoxum, Doros, Xanthogramma and Sphaerophoria). This is Sphaerophoria.
Pic Title: Male Platycheirus clypeatus front tarsi
Poster: stuart
Posted: Thu Jul 17, 2008 9:41 pm
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Pic Title: Sphaerophoria scripta genitalia
Poster: stuart
Posted: Thu Jul 17, 2008 9:38 pm
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Pic Title: Melanostoma female frons dust spots
Poster: stuart
Posted: Thu Jul 17, 2008 9:37 pm
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Pic Title: Yellow markings on the side of the thorax of Sphaerophoria
Poster: stuart
Posted: Mon Nov 28, 2005 9:21 am
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The presence of upstanding hairs on the top of the squama is a chracteristic feature of the genus Syrohus, but in other Syrphini the top surface of the squama is bare - although the squama (flap at the wing base) still has a fan of hair around the margin. This is Episyrphus balteatus.
The characteristic feature of the genus Syrphus is the presence of upstanding hairs on the top surface of the squama at the base of the wing. Once you know exactly where to look, this is quite an easy character (given good lighting), but it is essential to distinguish between the fan of hairs around the margins of the squama (which are almost universally present) and the sparser upstanding hairs on the top surface.
One of the trickiest couplets in the whole Stubbs & Falk (2002) key is the very first which asks whether the humeri and hairy (subfamily Milesiinae) or bare (subfamily Syrphinae). The hairy humeri of Milesiinae are usually fairly obvious because the head tends to be rounded behind giving a clear view of the humeri. It also helps in this specimen, Brachypalpoides lenta, that the pale hair stands out well against the black of the legs.
One of the trickiest couplets in the whole Stubbs & Falk (2002) key is the very first which asks whether the humeri and hairy (subfamily Milesiinae) or bare (subfamily Syrphinae). Unfortunately, in the latter the back of the head tends to be hollowed out and so fit over the front of the thorax obscuring the view - as this photo shows. Hopefully tou can make out the humeri down the gap, but beware of the hair around the humeri, but not actually on them.
Pic Title: Squama without upstanding hairs
Poster: stuart
Posted: Mon Nov 28, 2005 9:14 am
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Pic Title: Hairs on the squama of Syrphus
Poster: stuart
Posted: Mon Nov 28, 2005 9:08 am
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Pic Title: Hairy humeri of Brachypalpoides
Poster: stuart
Posted: Mon Nov 28, 2005 8:59 am
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Pic Title: Hairless humeri of Syrphus
Poster: stuart
Posted: Mon Nov 28, 2005 8:56 am
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Females of the two common species of Melanostoma are easily told apart by the dust spots on their frons (top of the head, between the eyes). This is M. scalare in which the dust spots are large and extend most of the way across the frons, almost meeting in the middle.
Wing of Hekophilus pendulus showing the loop in vein R4+5 which is characteristic of the Eristalini. This is used in couplet 5 of the Key to Tribes (Stubbs & Falk, 2002, page 59). The only non-Eristaline with this feature is Mereodon, and so it has been included in the Key to genera of Eristalini (Stubbs & Falk, 2002, page 138) so, when you see this feature, you can go straight to the generic key.
This trips a lot of people up! The first couplet in the key to genera of Xylotini (Stubbs & Falk, 2002, page 158) asks "GROUND COLOUR of face yellow or dark" and notes that, in the latter case it may be pale dusted. This photo of Criorhina shows clearly that the GROUND COLOUR is shiny black although the centre of the face is heavily yellow dusted.
The shape and position of pits on the INSIDE face of the 3rd antennal segment are used in the key to Brachyopa (Stubbs & Falk, 2002, page 130). This is the most frequent species, B. scutellaris, in which the pit is quite large and extends close to the lower margin of the antennal segment.
Pic Title: Dust spots on the frons of Melanostoma
Poster: stuart
Posted: Mon Nov 28, 2005 8:50 am
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Pic Title: Eristaline wing showing loop in vein R4+5
Poster: stuart
Posted: Mon Nov 28, 2005 8:48 am
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Pic Title: Has Criorhina got a yellow face?
Poster: stuart
Posted: Mon Nov 28, 2005 8:43 am
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Pic Title: Antennal pits of Brachyopa
Poster: stuart
Posted: Mon Nov 28, 2005 8:39 am
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