It isn't microevolution - it is macroevolution.
Beetles represent an order of the insect class. There are eight *families* of beetles. It is quite hillarious to see Creationists unwittingly admitting not only evolution above the species level, but also evolution above family level.
I don't think they realise how different various beetles are. For example most bettles lay eggs, but some beetles give birth to live young. So the Creationists here are saying that one of these reproduction types can evolve from the other.
Some beetles eat plants, others scavenge dead insects, some are parasitic. So the Creationists are saying that at lease some of these different feeding habits, and the systems to support them evolved.
From here: http://www.ivyhall.district96.k12.il.us/4th/kkhp/1insects/beetles.html
A unique form of predation among beetles is present with larvae of tiger beetles. Most beetles are active hunters of prey, but tiger beetle larvae, also known as "chicken chokers," wait in burrows in the ground. These larvae have a large bump on their backs that help them hold their bodies in the burrow. When an insect walks over their camouflaged heads, they grab the prey with long mandibles.
The Creationists have unwittingly claimed such a system and behaviour could have evolved.
Here is another one from the same site:
Larvae of long-horned beetles (family Cerambycidae) and metallic wood-boring beetles (family Buprestidae) bore in the wood of shrubs and trees, especially those that are dying or dead. The female twig-girdler, a kind of long-horned beetle, lays an egg at the end of a branch on a living tree. Then, the female chews, or girdles, the stem to cut off the water supply. The tip of the branch dies and usually falls to the ground. The larva of the twig-girdler then feeds inside the dead branch. Metallic wood-borers are known also as jewel beetles.
And here is a table comparing different families of beetles and the differences between them: http://tolweb.org/accessory/Beetle_Suborders?acc_id=422
It is interesting to note that some beetles are more genetically different from each other than humans and chimpanzees are different from each other.
And the tactic of saying "they are all just beetles" is ridiculous given the difference between beetles. Why stop at "just beetles"? Why don't we go up a level to the Subclass of winged insects? We could say Noah had a pair of winged insects on the arc and all the dragonflies,beetles, wasps and flies are just variation of that original kind. A beetle evolves into a wasp? No problem! It is still a winged insect. Microevolution.
Why not go up some more steps to the level of the phylum of Arthropods. We could say Noah had a pair of Arthropods on board which microevolved into spiders, insects, and centipedes. An insect evolves into a spider? No problem! It is still an arthropod. Microevolution.
Perhaps we could go all the way up to the animal kingdom and claim that Noah had a pair of animals on the arc. All animals around today are variations of that original animal kind. A doglike creature evolves into a bear? No problem! It is still just an animal. Microevolution!
It's all just being made up as they go along. Creationists have no idea where this mythical evolution barrier exists. Is it at the species level? The genus level? The family level? They don't know. I can imagine if someone had earlier suggested that weevils could evolve into fireflies (both types of beetle), the Creationists wouldn't be having any of it.