If it helps, Street Magic gives rules for insect shamanism - one of which is that it's NPC only!
... because anyone in their right mind will see an insect shaman, and promptly give him as bad a case of lead poisoning as they possibly can.
Personally, if I
knew I was going up against Insects, I'd take an ITS Gonryu if I could get my hands on it, and add MRSI software, because there's no such thing as too much Dakka.
Burst Fire, after fiddling with the overlapping explosion rules, means a net of 4 times the base grenade damage when you fire 2x Short Bursts with grenades using MRSI software. Although since it's 2 times base damage for 2 grenades, that's a bit of a Diminishing Returns situation, and you might be better off using Wide Bursts to spread the AOE over the largest area.
(Single MRSI / Triple MRSI)
HE Grenade = DV 20P/40P AP -2, -1/m radius
White Phosphorous Grenades = 16P/32P (Fire) initial + 8P/16P (Fire) for 10 Combat Turns, AP -Half, 10m radius.
Tough choice, there... probably take a belt (Yes, the Gonryu is
belt-fed 
) or two of each, since you never know if setting everything on fire will be a good idea or not until you're in the thick of it. Amiright?