The Giant Willow Aphid Tuberolachnus salignus at Potteric Carr YWT Nature Reserve, Doncaster 2025.

C.A. Howes & Les Coe

On 18 and 21 October 2025 CAH & LC visited Potteric Carr YWT Nature Reserve, Doncaster to continue making observations on colonies of the Giant Willow Aphid Tuberolachnus salignus (Gmelin). Contrary to observations made in 2024 when all monitored colonies had been on topiaried Osier Salix viminalis (see Howes, 2025), this year, populations were developing on a range of Sallow hybrids, particularly those growing along the metaled Main Access Road (SE591005 to 593004) leading down to the Mother Drain Pumping Station and the YWT Education Centre. With the Sallow shrubs being periodically cut back to prevent them obstructing the highway, or obstructing views onto Decoy Marsh there is a constant re-growth of young wood with 2nd or 3rd year stems proving attractive to T. salignus aphid colonisation.

During the visit of the Doncaster Naturalists’ Society with the British Plant Gall Society on 28 September, it was noticed that small groups of the T. salignus aphid were beginning to colonise these Sallows and while their presence was attracting the occasional Hornet Vespa crabro, the population was too small to produce the large volumes of Honeydew to attract the many diurnal nectaring insects as encountered on Osiers in 2024 (Howes, 2025).

By contrast, up to 23 days later, on our visits of 18 and 21 October, a preliminary search revealed at least 59 colonies, covering some 806cm of young sappy Sallow stems and honeydew was beginning to dribble down onto vegetation and autumn fruits below (notably onto Guelder Rose Viburnum opulus).

No attempt was made to identify the Sallows but mean leaf breadths and lengths from five colonised shrubs ranged as follows:

Table 1.
Leaf Sizes of colonised Salix’s
Breadth (cm) Length (cm) n sampled
2.7 12 10
3 10 10
3.5 7.5 10
7.5 12.5 10
7.5 14 10

The relative diameters of 59 colonised stems ranged from 0.2cm to 2.0cm, the mean being 1.01cm as shown in Fig. 1.

Figure 1.

The relative sizes (lengths) of the colonies ranged from 2cm to 45cm, the mean being 13.66cm as shown in Fig. 2.

Figure 2.

The majority of the aphids appeared to be fully grown wingless (apterous) specimens, though the larger populations had produced a few winged (alate) individuals capable of flight and therefore of colonising new sites.

Significant discovery: Occasional Harlequin Ladybirds Harmonia axyridis and the odd Hornet seemed to have been attracted by the honeydew, though the weather was probably too overcast and dull to attract many diurnal nectaring insects. However on 18 October, Les found attached to one of the sticky leaves a discarded forewing of a notably large moth. This was identified using Townsend, Waring & Lewington (2007) as the right forewing of a Clifden Nonpareil Catocala fraxini (formerly classified in the Noctuidae, now in the Erebidae). Its presence raised several interesting prospects relating to the food-chain created by the Willow Aphid Honeydew and to the changing status of the moth in South Yorkshire.

Firstly, before the days of light traps, 19th century lepidopterists used to attract moths to wine and honey-soaked ropes; so had this moth, a species known to be attracted by sweet substances, been attracted to the superabundance of the honeydew during the previous wind-free evenings.

Secondly, since the finding of the discarded wing of such a large moth can be field evidence of predation by Brown Long-eared bats Plecotus auritus, this raises the prospect of an interesting extension to the Aphid sugar food-chain.

Moth & Bat predator-prey adaptations: Many moths (and some other insects) have primitive ears, known as tympanic membranes, which are usually situated on either side of the third thoracic segment. Moths with these “ears” (tympanate moths) include members and close relatives of the Noctuidae (Faure et al. 1993; Fullard 1987). Tympanate moths and C. fraxini is one of them, are best able to hear the echolocation clicks of bats within the range of 20 to 40 KHz (Faure et al. 1990; Rydell et al. 1995). Aerial-hawking bats tend to emit within this range in order to locate prey accurately at a distance while flying. On hearing an approaching bat’s ultrasonic clicks, these moths will take evasive action, consequently many aerial hawking bats feed mainly on insects other than moths (Rydell et al. 1995).

On the other hand the Brown Long-eared Bat belongs to a group of bats known as “gleaning bats”, a substantial proportion of their diet being caught by “gleaning” prey items off vegetation, rather than by aerial-hawking (Anderson & Racey 1991; Shiel et al. 1991).

Gleaning bats (sometimes called “whispering” or “listening” bats) have relatively broad wings (for slow hovering flight) and large ears (for listening for fluttering sounds produced by their prey) (Anderson & Racey 1993; Greatorex-Davies et al, 2004).
Consequently a substantial part of the Brown Long-eared Bat’s diet consists of Noctuid moths as discovered at the Rossington Hall bat roost in the 1980s (Howes, in prep).

With the location of the (Potteric) Brown Long-eared Bat roost based at the secure equipment compound (SE593004), the species-rich hedgerow and deciduous woodland-edge vegetation along the Main Access Road would seem to be an ideal foraging habitat for this nocturnal flying mammal (Swift & Racey 1983; Entwistle et al. 1996).

The changing status of the Clifden Nonpareil: To quote from the Yorkshire Moths website
https://www.yorkshiremoths.co.uk/index.php?bf=24510&v=t
and Yorkshire Butterflies and Moths 2020 to 2024 (Butterfly Conservation & YNU),
“Porritt in 1883 was aware of four Yorkshire records from 1858 to 1875, with a fifth in 1896. This was however the last seen in the county until 1976. It was resident in the Norfolk Broads area and in Kent until the 1960s but then disappeared, only to reappear as a resident species in the south of England in about 2007. Until 2020 it only appeared in Yorkshire very rarely as scarce migrant, however the resident population in the south had been moving north at an ever increasing rate. In 2021 we had three records, then in 2022 an amazing 14 moths were seen, and it was suspected it was breeding in the south of VC63 [Austerfield]. In 2023 the invasion accelerated. We received 48 records of 51 moths from 37 sites spread fairly evenly over southern, eastern, and central parts of the county. 2024 brought a slight reduction, but we still had 34 records. It is now likely that many of these moths were colonists rather than migrants. The rate of advance has been astonishing and it will be fascinating to watch further progress.”

Recent local Records are as follows:
2020: Building up in the south of the county (Austerfield) as a native and an immigrant.
2021: Austerfield 7 Sept.
2022: Austerfield 3 caught in traps near Poplars 28 Aug; 18 & 22 Sept; Sprotbrough 5 Sept.
2023: Too many to list (!). Fishlake 19.9.23.
2024: Austerfield 7 (3 together), 8, 10 & 16 Sept; 16 Oct; from New Rossington 16 Oct and Hatfield Moors 8 Sept 24.

The species has only been known at Potteric Carr since 2024 when one was taken at light but dismantled by Hornet attack. It was also recorded in August 2025 (pers. com. Potteric Carr staff).

References:
Anderson, M.E. & Racey, P.A. (1991). Feeding behaviour of captive brown long-eared bats, Plecotus auritus. Animal Behaviour, 42, 489-493.

Anderson, M.E. & Racey, P.A. (1993). Discrimination between fluttering and non-fluttering moths by Brown Long-¬eared Bats, Plecotus auritus. Animal Behaviour, 46, 1151-1155.

Entwistle, A.C., Racey, P.A. & Speakman, J.R. (1996). Habitat exploitation by a gleaning bat Plecotus auritus. Physiological Transactions of the Royal Society of London Biological Sciences. 351, 921-931.

Faure, P.A., Fullard, J.H. & Barclay, R.M.R. (1990). The response of tympanate moths to the echolocation calls of a substrate gleaning bat Myotis evotis. Journal of Comparative Physiology. Part A. Sensory, Neural & Behaviour Physiology, 166, 843-850.

Faure, P.A., Fullard, J.H. & Dawson, J.W. (1993). The gleaning attacks of the Northern Long-eared Bat Myotis septentrionalis are relatively inaudible to moths. Journal of Experimental Biology, 178, 173-189.

Fullard, J.H. (1987). Sensory ecology and neuroethology of moths and bats: interaction in a global perspective. In: Fenton, M.B., Racey, P.A. & Raynor, J.M.V. (eds.), Recent advances in the study of bats. Cambridge University Press, Cambridge, pp. 244-272.

Greatorex-Davies, J.N., John, E & Arnold, H.R. (2004) Moth wings found at the feeding perch of a Brown Long-eared Bat (Plecotus auritus) in Bluntisham, Cambridgeshire, from 1980-1983 – a preliminary analysis. Entomologist’s Record and Journal of Variation. Vol. 116 (6): 241-257.

Howes, C.A. (Unpublished draft in Doncaster Museum 1996). Notes on the diet of a colony of Brown Long-eared Bats (Plecotus auritus) at Rossington Hall, Doncaster.

Howes, C.A. (2025) The willow, the aphid and the sugar-habit. The Naturalist 150, 1119: 146-153.

Rydell, J. (1989). Food habits of Northern Eptesicus nilssoni and Brown Long-eared Bats Plecotus auritus Bats in Sweden. Holarctic Ecology, 12, 16-20.

Shiel, C.B., McAney, C.M. & Fairley, J.S. (1991). Analysis of the diet of Natterer’s Bat Myotis nattered and the Common Long-eared Bat Plecotus aritus in the West of Ireland. Journal of the Zoological Society of London, 223, 299-305.

Swift, S.M. & Racey, P.A. (1983). Resource partitioning in two species of vespertilionid bats (Chiroptera) occupying the same roost. Journal of the Zoological Society of London, 200, 249-259.

Townsend, Waring & Lewington (2007) Concise Guide to the Moths of Great Britain and Ireland. British Wildlife Publishing, Dorset.

Yorkshire Butterflies and Moths 2020 to 2024 (Butterfly Conservation & YNU).