The lifetime of these bugs is too short. Bugs only live for 8 seconds, while cooldown is 3 seconds. Considering the low attack frequency for pet builds, it is so hard to keep the bugs at max numbers.

Lets see other temporary pets.
Black Scourge - lifetime 8 seconds, cooldown 3 seconds, 3 summon limit, 15% chance to summon, bugs have low health so easy to die.
Bonescavenger - lifetime 18 seconds, cooldown 4 seconds, 3 summon limit, 15% chance to summon, ghosts have high health.
Ghol Gloves - lifetime 18 seconds, cooldown 4 seconds, 3 summon limit, critical hit to summon, spiders have high health.
Black Hand - lifetime 15 seconds, cooldown 5 seconds, 3 summon limit, 50% chance to summon, moderate health.
Primal Instinct - lifetime 25 seconds, cooldown 2 seconds, 4 summon limit, 20% chance to summon, low health.
Easy to see that Black Scourge bugs have the shortest lifetime, and they are the hardest to keep at high numbers because of low health and low summon chance. Moreover, Black Scourge holds weapon slot, the most important and fiercely competitive slot. Weak bugs with low pet bonus makes Black Scourge underwhelming.
Suggestion
Increase their lifetime to 15 seconds to match other temporary pets, or 10 seconds with at least 25% chance to summon.
If possible, I hope to slightly increase their explosion range, maybe 3.5 to 3.8 meters.
p.s. Ghol Gloves need critical hit to summon, this is a bit strange. Few pet builds have enough OA and attack frequency to make critical hits.