These are dune snails, native to the Mediterranean region in Europe.

They are slightly smaller than the common garden snail, and are often found in groups in sunny sites.

These dune snails like sandy places, which is probably why they are not found around Ballarat.

However, they are not entirely coastal, with a range extending into at least the Wimmera in central west Victoria. They occur at Bannockburn too.

A feature of dune snails is their habit of massing together in exposed situations.

We would think that they would prefer to be out of the hot sun.

Their exposed grouping is thought to be due to the fact that they are slightly cooler up above the sandy ground, rather than on it.

Like most snails, they are active mostly at night.

At dawn they climb up - usually less than a metre - to their elevated positions, where daytime temperatures rarely reach more than 40 degrees.

They can apparently withstand temperatures of about 46 degrees.

Ground temperatures on sandy soils can be much higher.

Surprisingly, they seem to make no effort to use the shadier sides of any posts or fences.

Dune snails are serious agricultural pests, consuming a wide range of plant foods.

They have spread to many other parts of the world beyond their original Mediterranean range.

Some readers may be aware of "bee hotels", designed for the use of native bees and other native insects.

These consist mainly of short lengths of hollow bamboo stems in a frame, which small insects can use as nesting chambers.

Most of the holes are from 5-10mm wide.

A puzzle for the owner of one of these at Alfredton was the discovery of short, stiff grass-stems tightly-packed into the hollow bamboo and protruding out for a few centimetres.

The first report - with photos - shows three holes thus occupied.

The maker of these is the grass-carrying wasp, a small native insect.

Instead of plugging its nest holes with mud or some other sealant, it fills them with fine, stiff pieces of grass stem, presenting an unusual and effective barrier that would be difficult for any predator to remove or penetrate.

These wasps' nests are seldom reported, but they are probably not rare.

They would be easily missed. The spider stocks its nest with paralysed grasshoppers and crickets.

The latest word from our Alfredton correspondent says: "A friend in Buninyong also has a bee motel and has one 'occupant'. We now have up to 10 suites taken."

Can you ID this plant? It grows around swamps. It has a minty smell when the leaf is crushed. Is it a weed or native?

C.H., via email.

This is pennyroyal, a weed in the mint family.

Its mauve flowers are prominent in summer in some damp places.

Native to Europe, it is a true mint, growing to about 40cm, with numerous creeping stems and leaves at ground level.

It is now an environmental weed in southern Australia, spreading both by seed and root stems.

Crushed pennyroyal leaves have a reputation for deterring insects. There are several native mint species.

Locally we have four: river mint, forest mint, native pennyroyal and slender mint.

Pennyroyal has denser, rounder flower clusters than these native species.