Giant? Well, they were bigger than Jesus.
Giant beetles. I won't say they're unheard of in BX games I've played and run, but what I find amusing is that, even within the compactness of the Basic rules alone, we're given three varieties of them.
Beetles, Giant (from Moldvay)
|Hit Dice:||1 + 2||2'||3+1|
|Move:||120' (40')||120' (40')||150' (50')|
|Attacks:||1 bite||1 bite + special||1 bite|
|Damage:||2-8||1-6 + special||2-12|
|No. Appearing:||1-8 (2-12)||1-8 (2-12)||1-6 (2-8)|
|Save As:||Fighter: 1||Fighter: 1||Fighter: 1|
So right off the bat, we can see that they are basically a Small/Medium/Large progression. Fire beetles start off at about 2' long, finishing up with the Tigers at 4'. We also seen incremental increases in toughness and lethality. Also, they each appear in similar progression on the Basic (Levels 1-3) dungeon wandering monster tables.
The two "lesser" beetles are interesting because of their namesakes. Fire beetles -despite the scariness of the title- do not emit flames. Rather, each has three "glowing glands" that continue to emit light for up to six days after dying. It seems this critter solely exists to give low level PCs a brisk encounter and a free light source for the dungeon. Granted, 2d4 damage from its bite is a bad time for a 1st level PC, but that's what crossbows are for. Plus their morale is low.
Oil beetles spit a caustic fluid that penalizes the victim with painful blisters. It's interesting that a Cure Light Wounds spell will heal the blisters or the damage, not both.
Tiger Beetles are big, carnivorous, and dangerous. They are faster, tougher, and deal more damage (2d6!). It's also interesting that they have treasure. Type U doesn't yield much, but there's a chance of magic items!
The other tidbit about tiger beetles is that it mentions they usually eat Robber Flies. Which, as we've discussed previously, usually feed on Giant Killer Bees. One can imagine an interesting little food chain-based encounter sprouting up around this dynamic.