11 Across - Strange men filling a lake
15 Across - 6 multiplied by 500...brilliant
20 Across - Hermit crab from corner lab mutated
8 Down - Wily entomologist shares his tips about bad beetles
10 Down - Line erased trashed bosses
12 Down - Bird talk wildly nonsensical at first
(Sorry no letters any help really appreciated...J.Boy)