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The championships, which were first held in 2008, start in Argentina later this month.
University forwards Sam Dickson and Josh Hill trialled for the team, and made it through to the final camp, but did not make the cut.
It is a shame for the Southern unions, but far from a calamity for rugby in this region.
Picking junior teams is very much hit and miss.
For every player picked who went on to be an All Black, there are probably six players in the same Colts team who never went on to have a lengthy Super Rugby career.
Take the 2014 team, which was third in the junior championships in Auckland.
It produced five All Blacks in Damian McKenzie, Richie Mo'unga, Anton Lienert-Brown, David Havili and Atunaisa Moli.
But it also had team members such as Kaveinga Finau, Scott Mellow and Matt Peni, who quickly sank from the scene.
The 2013 team, which had the highest number of players from the South to make the Colts team (five) has produced players such as Scott Barrett and Ardie Savea, but there are also many misses.
Players mature at different rates, while others simply do not enjoy a high enough profile to get their name under the selectors' eyes, even though New Zealand Rugby has selectors right throughout the country to keep an eye on talent.
The New Zealand side going to Argentina will attempt to win the championships for the seventh time, but has plenty of catching up to do. It lost 24-0 to Australia last weekend on the Gold Coast.
NZ Colts team for the World Championships
Kaylum Boshier, George Dyer, Samipeni Finau, Devan Flanders, Cullen Grace, Kohan Herbert, Kianu Kereru Symes, Shilo Klein, Jeriah Mua, Fletcher Newell, Ollie Norris, Simon Parker, Taine Plumtree, Kaliopasi Uluilakepa, Tupou Vaa’i, Tamaiti Williams, Fergus Burke, Leroy Carter, Leicester Faingaanuku, Cole Forbes, Taufa Funaki, Scott Gregory, Lalomilo Lalomilo, Dallas McLeod, Billy Proctor, Rivez Reihana, Etene Nanai Seturo, Quinn Tupaea.