In terms of monthly shipments, Android devices surpassed Apple’s iOS lineup long ago. Apple executives and Apple bloggers repeatedly point to a different stat, however, that paints an interesting picture: Despite Android’s huge lead in terms of shipments, iOS remains the global leader in usage as measured by companies that monitor web traffic.

Unless the current trend is reversed in the next month or two, however, there will soon be a changing of the guard.

Net Applications is among the better respected firms that monitors global web traffic, and the company’s June data tells quite a story. For the second month running, iOS’s usage share has seen big declines as Android has continued to gain share at an impressive pace.

According to Net Applications, Android’s share of global combined smartphone and tablet usage rose to 43.75% in June from 41.58% in May and 37.75% in April. Meanwhile, iOS’s global share dipped below 50% for the first time in years in May when it fell from 51.11% to 48.34%. Then last month in June, iOS’s share dropped again to 45.61%.

At the current pace, Android will overtake iOS for the first time ever, though the lead may soon vanish as Apple prepares to launch two new iPhone 6 models and refreshed iPad tablets this fall.

As a depressing aside, BlackBerry is now officially part of the “other” category after having shown marginal gains in recent months.