Working on the smithing recipes you need a boat load (a big boat too) of these, 120. The bugs do only spawn during the day, worms at night, 7AM, 7PM, respectively. If you find them up at night they are just leftovers. The drop rate is probably closer to 1 in 10-20. I did not have any luck of them dropping during the night hours even though I killed some, but may have been coincidence. I killed everything bugs, nuisances, rockhoppers and worms and never ran out of mobs in that one area, respawn is fast. The name hopper, a blood drenched hopling spawned fairly often also. As far as the time, I just left an alt in PoK to check the time and people have previously mentioned.