I was struck by this image when looking through a book on First World War motorcycle uniforms, and I do believe this photograph shows the first instance of a 'skull and crossbones' (or Jolly Roger) logo on a motorcyclist's outfit. The photo was taken in Italy during WWI, and shows 'Renzo' on a Bianchi Model 500 A. Renzo ("waiting for action" it says on the back of the photo) was an Ardito (literally - 'audacious man'); the Arditi were the equivalent of Special Forces in the Italian Royal Army, created during a difficult period during the War for a specific job - to break a stalemate on the entrenched Italian Front. They were specially trained as an elite unit, with (according to 'Italian Arditi') "special recruitment procedures, training, arms, uniforms, priveleges, and benefits. For the first time, an Italian soldier was given concentrated, specific training, both psychological and physical; the Ardito also received the best available equipment and enjoyed superior living conditions. In order to counter the high casualty rate (!)... esprit de corps was very important..particular attention was focussed on comraderie and attitude, in order to motivtate the men and help them bear the psychological stress involved."
I've always been interested in the history of this symbol; there is evidence of origin on the flag of Roger II of Sicily (1095-1124), a sponsor of the Knights Templar. Former Templars flew Roger's flag when pirating at sea, after the Knights were disbanded. The image was later used by von Ruesch's Hussar Regiment #5 of the Prussian army in the early 1700's (see illustration below, from 1744), and around the same time was adopted by pirates, privateers, and corsairs plying the world's oceans (the first citation of the 'Jolly Roger' being 1724 - Charles Johnson's 'A General History of the Pyrates').
The Jolly Roger has been utilized by 'bikers' in the twentieth century for the same purpose - as a 'memento mori' (reminder of mortality), and to signify 'no fear' of death. The image has been modified in a thousand ways since this first, very simple logo on Renzo's riding outfit, but the message remains the same; don't mess with me.
The motorcycle is a Bianchi Model 500 A, a 498cc sidevalve single-cylinder machine with a short-leading-link front fork (see patent drawing from Jan 19th, 1915), a Bosch magneto, and Zenith carb. This was Bianchi's mainstay model, introduced in 1916, which dates the pic of Renzo between 1916-18, as the Arditi were disbanded after WW1.
I can't find much further information about the spec, but it would appear that this machine has a cone clutch inside the engine casting, plus a kickstarter, and a geared primary drive, all very advanced for 1915, although the final drive is still a single-speed belt. While similar in profile to the ubiquitous Triumph used by English despatch riders during WW1, the Bianchi is clearly a better-engineered machine - the clutch alone makes for a far more useful motorcycle. (In the detail photos, the engine uses a non-standard Binks carb).
The photograph of Renzo can be found in Aldo Carrer's amazing book 'The Motorcycle Uniform During the World War One' (sic - Zanetti, 2008). You can order the book (and his previous effort, 'The Dawn of the Motorcycle') from Aldo directly here. The photo is copyright Aldo Carrer, as it is from his private collection.
The Bianchi motorcycle photos are from 'Eduardo Bianchi' (Gentile, NADA, 1992), which is a lovely book in English/Italian.
The photo of the Arditos (knives raised!) is from 'Italian Arditi: Elite Assault Troops 1917-20' (Angelo Pirocchi, Osprey, 2008). As a further note, many of the Arditi joined Fascist paramilitary units just four years after WW1, to support Mussolini's rise to power. They were created about the same time as the Austro-Hungarian and German armies founded the Sturmtruppen - not a very romantic outcome.
For more information on pirates, I recommend 'Under the Black Flag; the Romance and Reality of Life Among the Pirates' (Cordingly, Harvest, 1995), which is the best book I've found on the subject.