What is this old US Army Air Corps plane?
Well gosh, this is a rare bird! The 'DEHAN' monoplane:





From this forum:


  More about Dr.Ing. Jacob Emil Noeggerath (Nöggerath ?),from the first
  Lange's book :
  
  He had in 19011/12 the HUNGARIAN " DEHAN ":) monoplane designed ,wich
  was flown at München-Oberwiesenfeld.
  
  There is another short passage about it in the Etrich book by Hanuš
  Salz.
  
  Dr. med. Theodor Dieterle let built this monoplane in the Otto works
  in Munich in 1913. He was supported by J.E. Noeggerath (not Nöggerath)
  who corresponds with Etrich since 1911 and was probably involved in
  the design too.
  
  It had an unusual longitudinal stabilisation system with a sort of
  tank? at the front that later was removed.
  
  Hanuš Salz named it "Dieterle Schwalbe" or "Taube" only. I prefer the
  term "Schwalbe" as the wings are peaked and the tail even it is not
  splitted but inward curved and not Taube-like.
  
  After this machine was tested with the swiss army, they contacted
  Etrich as well. Only an order for his machines was not realised.


So, it would appear that the plane was a one-off, commissioned by two medical doctors in Zurich, designed by Etrich (hence the similarity of the wings to those of the Taube), built in Munich and flown in Switzerland.

Which does, of course, leave another question: how did it turn-up in Texas in 1918? (Or did it?)

Edit:
There is quite a lot more info on this page under the name 'Dieterle Schwalbe'. In particular:  


  Als Besonderheit verfügte die ‚Dieterle-Schwalbe‘ vor der Rumpfnase über eine mit Bleischrot gefüllte, jederzeit verstellbare Metallkapsel von ca. 10 kg. Mit diesem Vorgewicht konnte der Aeroplan während des Fluges ausbalanciert werden. Mit der Lenkbarkeit und dem Sturzflugverhalten von Flugapparaten hat Dieterle sich intensiv beschäftigt und seine Erkenntnisse in mehreren Bulletins des Aero Clubs 1914/15 veröffentlicht. Ob das Resultat seiner Forschungsarbeit in die Entwicklung späterer Sturzkampfbomber wie der Ju 87 eingeflossen ist, kann vermutet werden.  


Google translation:  


  As a special ordered that, Dieterle Swallow 'in front of the fuselage nose over a column filled with lead shot, at any time adjustable metal capsule of about 10 kg. With this pre-Wicht of Aeroplan could be balanced in flight. With the steerability and the nosedive of Aerial equipment Dieterle has intensively and published his findings in several bulletins of the Aeroclub 1914/15. Whether the result of his research has gone into the development of later dive bombers like the Ju 87, can be suspected. 


In other words, Dieterle specially ordered that there be 'pre-weight' canister of about 10kg lead shot attached forward of the fuselage and which could be adjusted in flight to balance the aircraft.




Caption reads: "The 'Dieterle Swallow' with the characteristic Pre-weight; Oberwiesenfeld January 1913"