UPDATE August 2018: with the recent acceptance of the 2008 record from Hidalgo county (see this page) this becomes the second record for Texcas.
These two male White-tailed Sylphs Macrothemis pseudimitans were on San Felipe Creek, Del Rio, Val Verde county, Texas on May 09, 2014. They are the first confirmed records for Texas, and the third for the U.S. (two fairly recent records from Arizona) - but see this page for what was very probably this species in Texas in 2008. :
01) This first individual was patrolling a short beat close to the bank:
- on these zooms note the distinctive shape of the "club", and also the cerci:
02) This second individual was patrolling a short beat close to the bank, about 100 yards from the first individual:
In this combination image you can see small differences in the shape and size of the pale marks on the abdomen, establishing that these photos portray seperate individuals. Also note the shared features that distinguish this species from Ivory-striped Sylph (M. imitans/imitans leucozona):
A: the two well-separated pale "lozenges"
anteriorly on the side of the thorax.
B: the pale blue frontal marks extending down to a fine point almost to the bottom of the thoracic frontal plate.
C: the very small pale marks on S6.
D: the large size of the S7 pale marks, which are matching non-symmetric trapezoid shapes that almost touch for their entire length along the central ridge, and have a "flat" rearmost edge.
This male Ivory-striped Sylph was photographed by Troy Hibbitts at Las Moras Creek, Fort Clark Springs, Kinney County, Texas in June 2012:
A: the two pale "lozenges"
anteriorly on the side of the thorax are thinly connected (can have a complete but very thin break).
B: the pale blue frontal marks extend less than half-way down the thoracic plate, ending in a short, broad, blunt point.
C: the large pale marks on S6.
D: the smaller size of the S7 pale marks, each of which is a rounded oblong or a "soft" trapezoid, with a rounded/pointed rearmost edge.
This male Ivory-striped Sylph was photographed by Troy Hibbitts at Montell Springs, Uvalde County, in July 2010; the same features are highlighted; note also the different shape of the "club" and the cerci compared to pseudimitans: