Summon Mephit

[Quidam]

Mephits have a 25% chance of summoning another mephit of the same type. How long do these guys stick around? It says "much like summon monster" but it also says that new mephits can't use their summoning power for an hour.

 

[Krafen]

"As summon monster" would mean 1 round/level. Mephits have 3 HD, so I guess the summoned mephit would stay for 3 rounds.
The SRD entry says:

Summon Mephit (Sp): Once per day, all mephits can summon other mephits much as though casting a summon monster spell, but they have only a 25% chance of success to summon one mephit of the same type. Roll d%: On a failure, no creature answers the summons. A mephit that has just been summoned cannot use its own summon ability for 1 hour.

On the other hand, the SRD entry for Tanar'ri says:

Summon Tanar’ri (Sp): Tanar’ri can summon other tanar’ri much as though casting a summon monster spell, but they have only a limited chance of success. Roll d%: On a failure, no tanar’ri answer the summons. Summoned creatures automatically return whence they came after 1 hour. A tanar’ri that has just been summoned cannot use its own summon ability for 1 hour.

It could be the Mephit is supposed to be able to summon another Mephit for a full hour, in which case the restriction on the summoned Mephit's own summoning ability would make sense. I didn't find an entry for Summoning under Special Abilities in the DMG.