TECHNICAL | PPC113 November 2023
In this seasonal special, Paul Westgate, from Veritas Pest Consultancy, takes a look at what or who could be lurking in our lofts during the winter.
To humans, the loft is just a storage place, somewhere to stash boxes of seldom used belongings, Christmas trees, suitcases and old toys.
For other animals, especially insects, the loft provides a refuge, a winter holiday resort. In their minds, the domestic loft is simply a heated tree, a habitat to occupy (albeit for many only on a temporary basis).
Many of the creatures that check in as the temperatures begin to fall in autumn are welcome guests; residing during the coldest months of winter and checking out in the spring once temperatures climb again. They complete their stay without fuss and without nuisance.
However, some are not so courteous or indeed welcome; they provide concern, discomfort and, like a jack-in-the-box, a surprise waiting to pop out later on in the year.
Mammals
Bats
Bats in the UK are highly protected; bats, their roosts and access to their roosts are protected under the Wildlife and Countryside Act 1981.
There are some 17 species of bats in Britain, which represent about a quarter of all species of British mammals.
One of the most common and well known, the pipistrelle bat (Pipistrellus pipistrellus) has an estimated population of around three million individuals.
This small bat is capable of eating around 3,000 insects per night and can regularly be found taking up residence in a loft space.
Bats commonly begin to check-in to their hibernation sites towards the end of October, emerging in early March.
Identifying the presence of bats is an important step when planning rodent or insect control work. Scattered piles of droppings similar in size to those left by mice, which crumble when squeezed, are perhaps the most obvious signs of these animals.
Their stay presents no direct issues but they may not be welcomed by all, and pest controllers should beware: fines for disturbing or interfering with a bat colony are severe.
Luckily, the Bat Conservation Trust provides excellent guidance and support for those domestic properties lucky enough to have bats roosting in a loft, plus excellent documentation to support pest control work.
Edible dormice (Glis glis)
In certain parts of central England, another resident may be encountered during the winter months: the edible dormouse (Glis glis).
This introduced invasive species is now thought to number in excess of 25,000 individuals, largely throughout the Chilterns. They can overwinter in buildings, especially lofts where they present the same risks as the other more commonly encountered rodent species.
However, treatment is very different from their rat and mouse cousins, with a class licence needed before controls are applied (this is largely to support understanding of their distribution).
See ‘Edible dormice: licence to trap them (CL02)’.
No rodenticides are permitted for use on Glis glis and, aside for live capture and humane dispatch, only those traps listed on the Spring Traps Approval Order (and its associated variations) are permissible for use.
Insects
Cluster flies
Perhaps the most well-known and frequently encountered insect loft guest is the cluster fly (Pollenia rudis).
This medium size fly – in its larval stage a parasite of the humble earthworm – enters loft spaces in sometimes biblical proportions during autumn.
The cluster fly is one of a number of species from the Polleniidae family and is perhaps the most obvious and bothersome of the loft’s winter occupants.
A useful key for their identification can be found at ‘Mike’s Insect Keys’.
These flies, although not directly linked with disease transmission, do present a risk to reputations.
And they are bothersome and unwanted. Cluster flies often require treatment with insecticides, or carefully placed and serviced electric fly killers.
Other flies
A large number of other Diptera (true fly) species overwinter in the adult stage within lofts, and although not in the same numbers as the cluster fly it is common to find members of the blow fly (Calliphoridae) family, such as the bluebottle (Calliphora spp.) and greenbottle (Lucilia spp.).
You may also see some Muscidae species (identifiable by bent fourth wing veins) such as the green cluster fly (Eudasyphora cyanella) and the autumn fly (Musca autmnalis).
Another fly of significance, from the grass fly family (Chloropidae), is the yellow swarming fly (Thaumatomyia notata). It has a distinctive yellow and black striped thorax and a similar size to the ubiquitous fruit fly.
They can build up in such significant numbers that irritation, repulsion and reputational damage can occur wherever these flies swarm in public facing areas.
Wasps
Queen wasps are regularly-encountered loft occupants, and the only member of the colony which survives the winter period.
The fertilised queen can often be found biting down on timber structures, remaining hidden in cracks and crevices, and awaiting the return of warmer times.
Queen wasps often check in earlier than many of the other loft ‘residents’ and their hibernation can begin well into the summer months.
When temperatures increase in spring the queens will set about the construction of their golf ball-sized nest which, if conditions are favourable, will soon develop into a thriving nest of many thousands of individuals.
Read BPCA’s Pestwatch: Queen wasps.
Lacewings
Bright green or brown insects from the Neuroptera order of insects are often noted by homeowners.
These lacewings are aphid-eating predators and often congregate in reasonable numbers in the loft.
Their presence is not usually significant and (in most cases) they will see out the winter unnoticed.
Butterflies
Another group of insects which largely undertake their stay unnoticed are the Lepidoptera.
Several species of butterfly overwinter in the adult stage, in contrast to the majority of butterflies, which will overwinter in the pupal, larval or egg stage.
Two common flamboyant examples include the peacock (Aglais io) and the small tortoiseshell (Aglais urticae).
Ladybirds
The harlequin ladybird (Harmonia axyridis) is a recent introduction to the UK. Arriving around 2014, it was bought to help control insect pests (aphids, thrips etc) within the glasshouse industry.
These aphid-eating machines, selected for their ferocious appetite, rapidly left the confines of the greenhouse and entered the ecosystem of Britain, where they are now commonplace.
Harlequin ladybirds cluster together, often in lofts, roof spaces and around window frames.
They can cause minor damage to fabrics, furnishings, and have the potential to bite.
However, it is their impact on the environment which is perhaps far more problematic.
There are reports that classify their impact on native ladybirds and other beneficial invertebrate species as somewhat significant.
“These aphid-eating machines... rapidly left the confines of the greenhouse and entered the ecosystem...”
You’re a fool, if you dare
While the loft may seem a quiet, lonely and eerie place, in the animal world it is a temporary lodging; a hotel or a waiting room for better times, better conditions and a more favourable environment.
For a pest controller, when undertaking work in loft areas, be sure to check out who’s in town and who’s checked in for a long winter.
But remember, just like Berk from the 1980s Trapdoor kids’ TV programme; be careful when you open that trapdoor, because there’s something lurking ‘up’ there!
Find out more
For more information about insects and their identification, why not book onto a BPCA insect identification course, where you can improve your identification skills and facilitate the correct treatment.
bpca.org.uk/find-training