Snail and Slugs

If you think that snails and slugs are hibernating now, you could not be more wrong.

To my great surprise in December, I found an adult Garden Snail (Cornu aspersum) crawling along in the middle of the day, in full view.

Then I was told by an expert, Simon Taylor, that snails only avoid extremes of cold or dry heat. Admittedly it was a mild winter morning. But perhaps this snail was an exception, because when I checked one of their favourite well-hidden hibernation spots in our garden, they were still there - loads of them.  See a sample below.

These hibernating snails have been there for quite a while. On the bottom left of that picture, note the pale epiphragm on the unattached snail. Hibernating snails stop feeding and seal the aperture of their shell with a sticky substance, which is called the epiphragm. The epiphragm is composed of dried mucus that can easily be dissolved. It protects the snails from extreme weather conditions.

Also, above that snail there is a chain of translucent lemon-shaped eggs; they belong to the Irish Yellow Slug (Limacus maculatus). This distinctive slug is omnivorous; it is often found in compost heaps in great numbers, under logs, etc. It is active at this time of the year.

These are the only slug’s eggs that I can identify, because they are translucent. Most of slug’s eggs are creamy-white and opaque. See below.

Creamy-white slug eggs need to be reared in other to find out who laid them. I’ve done just that indoors with a cluster of creamy eggs that I picked at the end of September; they took about four weeks to hatch and I’m rearing just two of them on lettuce leaves. I will keep you posted when they reach maturity.  However, in the field I have no idea how long they take to hatch.

While some slugs hibernate deep in the soil after reproducing, this is not the case with others. For example, on the same day, I found several Budapest Slugs mating under logs in the Irvine Road orchard. This keeled slug was very common in my old allotment plot. 

Other slugs are simply active all the year round, like the above mentioned Irish Yellow Slug. Another one is the supposedly rare/under-recorded carnivorous Shelled Slug (Testacella haliotidea) but is surprisingly common in our garden and old allotment plot. I find them all the year round under a mulching membrane that I use in our back garden. It is an ideal habitat for snails, slugs and earthworms the favourite food of the Shelled Slug.

Under the cover of night, quite a few species go out foraging at this time of the year. In our back garden they go for the chicories. The commonest slug is the oatmeal coloured Deroceras reticulatum which is (in-)famous for its love of lettuces. 

In the front garden its slightly darker close relative, Deroceras invadens, outnumbers all the other visitors to the flowers of a Winter Iris (Iris unguicularis) plant which are extremely popular during the night. These night visitors find the flower stems and petals delectable and in the process do a lot of damage.

To give you an idea of some of the other Winter Iris visitors, below is a snapshot of a night catch, soon after the very cold spell in early January ended.

I’m having trouble with the identification of the tiny snails, though. On top of these, I have seen foraging there the above mentioned Irish Yellow Slug and tiny Garden Snails. The latter probably hatched from late laid eggs already. Just a guess.

Even though I’ve not told you about all the active species, I must stop now as this is by far my longest Nature News piece. I hope that I’ve convinced you that slugs and snails are active at this time of the year in our gardens and allotments - they never stop. Of course, they know where the most delectable plants are being cultivated - they have refined tastes like us.

Further reading:

• Fremlin, M. & Taylor, S. 2022.  Further observations on the carnivorous slug Testacella haliotidea Draparnaud, 1801. Essex Naturalist (New Series) 39: 66-73. [PDF]

• The best sites for snails and slugs are probably https://www.naturespot.org/ and www.inaturalist.org.