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Species of the month

Every month it is our aim to highlight a species that is “in-season” and, although not necessarily rare or difficult to identify, has been highlighted by our local recording groups as being somewhat under-recorded and for which new records would therefore be welcomed.

If you or your recording group are aware of species such as this then please contact Bob Foreman.

 

May: The Spring Fritillaries (Boloria sp.)

Pearl-bordered Fritillary

Pearl-bordered Fritillary (Boloria euphrosyne)
Upper-wings
Photo: Neil Hulme

Pearl-bordered Fritillary

Pearl-bordered Fritillary (Boloria euphrosyne)
Under side
Photo: Neil Hulme

Small Pearl-bordered Fritillary

Small Pearl-bordered Fritillary (Boloria selene)
Upper-wings
Photo: Neil Hulme

Small Pearl-bordered Fritillary

Small Pearl-bordered Fritillary (Boloria selene)
Under side
Photo: Neil Hulme

Sussex is currently blessed with approximately 50 species of butterfly, some of these are only occasionally observed scarce migrants, others are from well-established breeding populations. Among these species is a small group of predominantly woodland-dwelling nymphalids, the fritillaries. The Silver-washed Fritillary (Argynnis paphia) as a familiar sight in late summer when it is likely to be encountered flying at speed along the rides of most "good" woodlands. Slightly smaller than the Silver-washed is the Dark Green Fritillary (Argynnis aglaja), a species that can also be common in Sussex and although it will be seen in woodlands is more likely to be found flying in the flower-rich chalk grasslands of the South Downs during mid-summer. However, there are two species which are far less frequently seen; the Pearl-bordered (Boloria euphrosyne) and Small Pearl-bordered Fritillaries (Boloria selene). All four of these fritillaries have similarly patterned upperwings, deep orange with an array of black spots and stripes, their larvae all feed on violets too. Differentiating the latter two species is somewhat trickier though.

The Pearl-bordered Fritillary is a medium sized butterfly with blocky black spots distributed evenly over its orange-brown upper-sides. The underside of the hind-wing is reminiscent of a stained glass window, being divided into numerous polygonal cells, and edged with a string of seven silvery white ‘pearls’. In all these respects it is very similar to the marginally smaller Small Pearl-bordered Fritillary.

The underside of the hind-wing in the Pearl-bordered Fritillary has a warmer look to it than that of its close relative, being a mix of earthy yellow and orange-brown. There are two silvery white polygonal cells in contact with the inner-central pentagon, which contains a small black spot.

The underside of the hind-wing in the Small Pearl-bordered Fritillary shows greater contrast, being a mix of cream and deeper red-brown. There are at least half-a-dozen silvery white polygonal cells in contact with the inner-central pentagon, which contains a significantly larger black spot. Also, the black lines which outline each polygonal cell are bolder in this species, and there are black spots situated inside the seven marginal ‘pearls’, adding to the greater contrast and generally darker appearance.

The most marked difference between these two species and their commoner relatives is the almost catastrophic collapse in their populations that has taken place in the south east of England in recent years. Of the Small Pearl-bordered Fritillary, Colin Pratt wrote the following in his 2011 county history: "For well over a 100 years, up until the mid 1970’s, this butterfly could be found in most suitable woods from one end of the county to the other - approaching 150 colonies had been discovered". Throughout much of its long history here, it was more numerous than the Pearl-bordered Fritillary. The last Small Pearl-bordered Fritillary of Sussex descent ever to fly in the county was seen on 29 June 2013. At some point during the first week of July that year the species went extinct, both locally and regionally.

The Pearl-bordered Fritillary or the ‘Woodman’s Friend’, as it was once affectionately known, was common in the days when many woodlands were actively worked for coppice products and charcoal. The butterfly would follow the woodman, as he moved around creating open areas in which the Common Dog-violet would flourish, until the canopy began to close again. In Colin Pratt’s words: "Up until around the middle of the 20th century this Fritillary occurred in numbers undreamed of by modern butterfly enthusiasts; it could often literally be seen in hundreds and occasionally even in thousands". Butterfly Conservation’s ‘The State of the UK’s Butterflies 2015’, produced by Richard Fox and colleagues, points to a 95% drop in this species’ national occurrence index (1km square occupancy) between 1976 and 2014.

As elsewhere, the population of Pearl-bordered Fritillary in Sussex has collapsed, and its geographical range contracted to just a few refuges. In recent years it has become restricted to just two strong population centres, at Rewell Wood in West Sussex, and Abbot’s Wood in East Sussex, following a successful re-introduction.

Despite it becoming extinct in 2013 in south east England, the Small Pearl-bordered Fritillary is again flourishing in its last stronghold of Park Corner Heath and Rowland Wood thanks to a captive breeding and reintroduction programme carried out under the auspices of the ‘Fritillaries for the Future’ project led by Neil Hulme and involving a small group of dedicated volunteers. The breeding stock for this came from Bentley Wood on the Hampshire-Wiltshire border.

Although both of these species are known as woodland inhabitants, the Pearl-bordered Fritillary was once also to be found in more open habitats; heathland and more scrubby parts of the Downs. Compared to the Small Pearl-bordered Fritillary it has a definite preference for the warm, dry clearings created in coppiced of woodland. The Small Pearl-bordered Fritillary’s habitat preference is for much damper woodlands with areas of standing water or permanently damp rushy rides. It is this preference that is thought to be a major factor in the species’ decline in Sussex as Climate Change dies out our once damp woodlands.

Both of these species fly earlier in the year than their larger relatives, the Pearl-bordered being the first to appear, usually in late April through to early June, in the early part of the 20th Century there was occasionally a partial second brood in late summer. The Small Pearl-bordered Fritillary’s flight period is about three weeks late than Pearl-bordered from mid-May through to the End of June, again with occasional partial second broods in August.

All records of these butterflies are particularly welcome and if you are luck enough to encounter either species please send the details either directly to bobforeman@sussexwt.org.uk at the SxBRC or enter them on iRecord.

 

 

April: Tapered Drone Fly, Eristalis pertinax

Male Eristalis pertinax - photo: Steven Falk

Male Eristalis pertinax Beachy Head, East Sussex. Note that pronounced bulge in one of the wing’s veins which identifies it as one of the Eristalini hoverflies.
Photo: Steven Falk

Female Eristalis pertinax - photo: Mike Mullis

Female Eristalis pertinax Herstmonceux, East Sussex
Photo: Mike Mullis


Male Eristalis pertinax - Photo: Mike Mullis

Male Eristalis pertinax Herstmonceux, East Sussex. Note the yellow tarsi (‘feet’) on the front and middle legs compared to the dark tarsi of the hind leg.
Photo: Mike Mullis

Eristalis pertinax distribution

Map showing scattered distribution of Eristalis pertinax records in Sussex. The apparent coastal and downland bias may well be a result of recording effort rather than a true reflection of distribution.

Everyone loves bees don’t they? The recent revelations that our bees are in decline has prompted protests and petitions and have highlighted the vital service these buzzing pollinators provide to our planet. Yet many other pollinators which provide the same service don’t get the same level of public support. So in April I’m raising my banner for the hoverflies.

There are almost 300 species of hoverfly in the UK and one of the first to appear each year is Eristalis pertinax - the Tapered Drone Fly.

At first glance you may mistake this hoverfly for a honeybee but that’s exactly what Eristalis pertinax wants you to think. This isn’t an attempt to jump on the bee bandwagon to win some attention - it’s all a cunning strategy called Batesian mimicry. The UK’s hoverflies come in many shapes, colours and sizes but most of them sport yellow/orange markings and black stripes making them easily confused for wasps, bees, hornets and bumblebees. But unlike bees and wasps hoverflies are harmless. They don’t sting and can’t bite. But they have discovered you don’t have to actually be dangerous to deter predators - you just have to look like something that’s dangerous. It’s a strategy you can try for yourself. To avoid unwanted attention simply strap on a fake bomb and a wear a big hat with TERRORIST in big letters across it and I guarantee nobody will want to talk to you. Except maybe the police.

Some hoverflies are so much like bees and wasps that only their mother could tell them apart (check out my favourite - the furry bumblebee mimic Eristalis intricarius) yet their devious mimicry isn’t the most incredible feature about them. Their wings are the things. Hoverflies (like all flies) have just two wings (half as many wings as bees and wasps). The looped wing venation is a way to identify the Eristalini and Eristalis pertinax has that noticeably tapered abdomen and the front and middle tarsi (the end section of the leg) are yellow.

Whereas other flies keep their wings straight hoverflies have the inclination to incline their wings and an angled downward stroke at a remarkable rate of 120 beats per second allows them to fly to a most amazing place: nowhere. Hoverflies have become the motionless masters of mid-air. In April you’ll spot Eristalis pertinax doing just that - hovering around sunny woodland rides defending its territory.

The looped venation on their wings is a way to identify the Eristalini and Eristalis pertinax males have that noticeably tapered abdomen and in both sexes the front and middle tarsi (the end section of the leg) are yellow.

It’s not all sitting around in the sky though. During their few days of life hoverflies fight, fornicate and feed. While busy collecting energy-giving nectar and protein-rich pollen they inadvertently provide that vital pollination service to our flowers and crops. And hoverflies have earned the title of ‘The Gardeners Friend’. About 40% of them have a larval stage which is basically a tiny crawling stomach that roams around your flowerbed eating pesky aphids. Pollination, pest control - next thing you know these beneficial little insects will be mowing the front lawn for us too.

Eristalis pertinax larvae however are, like many other species, aquatic and filter feed on the tiny organisms found in decaying matter in ponds. These type of hoverfly larvae breathe through a long tube and have earned the name ‘rat-tailed maggot’ a phrase I find pleasing to mention under my breath each time Nigel Farage appears on TV.

If you’re interested in recording hoverflies I’d recommend the excellent identification guide ‘Britain’s Hoverflies’ by Stuart Ball and Roger Morris. Steven Falk has an impressive catalogue of hoverfly photos on his Flickr site. To become more involved with fly recording in Sussex join the Sussex Fly Group who organise field trips and indoor identification sessions throughout the year.

Michael Blencowe, Sussex Fly Group

 

 

March: Brown Hare Lepus europaeus

Brown Hare photo Damian Waters

Amber eyes and ears with black tips: Hare
Photo: © Damian Waters/Sussex Wildlife Trust

Brown Hare photo Bob Eade

The sit tight philosophy.
Photo: © Bob Eade/Sussex Wildlife Trust

Map of Brown Hare records in Sussex

Map showing where Brown Hares have been seen in Sussex but also large areas without any records

When we muse upon all things March, the mad hare has got to be up there. The Brown Hare is the most widespread of the two UK species, and the only one you’ll spot in Sussex. They are creatures of open country. Vegetarian grazers, occasionally indulging in a spot of browsing saplings. With a home range of some 50 hectares, their movement patterns track availability of fresh plant growth. Hares thrive in areas that provide grassland alongside arable land that incorporates cereals, leys, margins and winter stubbles; meeting their appetite for seasonal food.

Hares are naturalised mammals, and who introduced them is still disputed. Usually the Romans are implicated, although there are those that maintain their introduction pre-dates this, and they instead arrived some time during the Iron Age. Whenever they got here, I always get a thrill seeing a hare blazing its zigzag trail across the South Downs, nothing but chalk dust in its wake. If you’re still clarifying the difference between rabbits and hares in your mind. Did the ears have black tips? Hare. Did those amber eyes fix you with a slightly unnerving stare? Hare. Was there big air as it bounded away, propelled by long hind limbs? Hare!

Hares often specialise in the sit tight philosophy. I saw one a couple of weeks back, a just visible lump of primed muscle, long ears flat along its back. Waiting for me to get close enough. Adrift in the middle of a field, which on first appearance seemed stupidly conspicuous, this fitted with hares’ often used predator avoidance strategy. No danger of being sneaked up on here (unless Luna the Eagle Owl makes another bid for freedom). When you do reach their flight zone, hares often hold their tail downwards, concealing the white flag of its underside, as they beat their 45 mph retreat.

And the boxing? Two males sparring for attention? No. This is a female, telling an overly-amorous male to back off, as she approaches oestrus. Hares aren’t renowned for their parenting skills. A female can expect to give birth around 40 days after mating, with the first leverets usually arriving during February. As soon as they are born, the female leaves her young, indulging them with just a few minutes of her time each day, for just over a month until they are weaned.

A new threat has recently entered the hares’ world. Myxomatosis is already known to make the leap from their rabbit cousins, with the first confirmed UK mortality of a hare from Somerset in 2014. It now seems that another virus, RHD2, can also kill hares, being recently linked to deaths in Essex and Dorset. Anyone finding a sick or dead hare is asked to send a photograph of it to Dr Diana Bell at the University of East Anglia https://www.uea.ac.uk/about/-/uea-researchers-to-investigate-mysterious-hare-deaths who is researching hare die-off across the UK. The map above shows some of Sussex’s hare hotspots - the South Downs, as well as areas of grazing marsh, but highlights large areas with no records. If you spot a hare in Sussex please report your sighting to SxBRC, to make sure they contribute to Sussex Mammal Group’s new online mammal map https://sxbrc.org.uk/mammals/mapping.html#.

Laurie Jackson, Sussex Mammal Group

 

 

February: Common Toad Bufo bufo

Common Toad

Common Toad Bufo bufo at Knepp
Photo: Ryan Greaves

Common Toad heat map

Heat map of Common Toad records in Sussex, the red squares show where most records have been collected.

The Common Toad (Bufo bufo) is a solitary creature, spending the majority of its life on land buried in leaf litter, under tree roots, in log piles and in vegetable patches. Basically anywhere slightly damp where there is an abundance of invertebrate prey. However like all our native amphibians, Common Toad must return to water in spring to breed, sometimes travelling over 2km to get to their preferred pond.

Common Toad has dry warty skin and brilliant golden-bronze eyes with dark horizontal pupils. They are generally described as brown to olive brown, but colour can widely vary with some very dark or very red individuals. Additionally, a key identification feature are the large paratoid glands that stick up behind the eyes. These glands produce bufotoxin, an alkaloid neurotoxin that helps to defend against predation.

Common Toad have much shorter legs than Common Frog and tend to crawl or hop, rather than make large jumps. They also differ in their choice of breeding pond, generally preferring much deeper, larger bodies of water compared to the shallow pools where frogspawn can often be found. Common Toad-spawn is also very distinctive, being formed of long strings of a double row of eggs draped around submerged vegetation like a pearl necklace.

At this time of year Common Toad may be seen migrating back to their ancestral breeding pond, often disregarding any barriers that have appeared, including busy roads and deep drains. They tend to travel at dusk, most commonly emerging from their overwintering site after a spell of damp, warmish weather (air temp of 7-8°C). Unfortunately this can often coincide with peak car commuting times and scores of Common Toad can be killed as they try to cross roads.

Whilst, Common Toad is widespread in Britain, populations have declined dramatically over the last century and it is now listed as a Priority Species of Conservation Concern. Declines are largely due to habitat fragmentation and a huge loss of breeding ponds. However, the species is also generally under-recorded, so any sighting, especially of migrating or breeding Common Toad, is desirable. The map above shows where Common Toads have been recorded but also highlights the large areas of Sussex from which we do not have any records.

Please report any sightings of Common Toads either to iRecord, or by email to bobforeman@sussexwt.org.uk with details of location, grid reference and date found.

 

 

January: Hemp-agrimony Plume, Adaina microdactyla

Adaina monodactyla

Adult Hemp-agrimony Plume Adaina monodactyla, Rewell Wood
Photo: Colin Knight

Adaina monodactyla larva

Larva of Adaina monodactyla, in stem of Hemp-agrimony
Photo: Colin Hart

Adaina monodactyla gall

Hole produced by Adaina monodactyla larva in gall formed in stem of Hemp-agrimony
Photo: Colin Hart

Adaina monodactyla distribution

Distribution of records of Adaina monodactyla in Sussex
Map from Sussex Moth Group website

There are 44 members of the Pterophoridae or plume moth family that occur in the UK of which 30 have been recorded in Sussex. The smallest of these, with a wingspan of around 15 mm, is the Hemp-agrimony Plume Adaina microdactyla, although not rare it isn’t a commonly recorded species but is one that, according to County Recorder, Colin Pratt, is believed to be on the increase in Sussex.

The plumes are all small moths, with a wingspan of no more than about 30 mm. Their wings are deeply cleft or lobed into feathery "plumes", the forewing being divided into two and hindwing into three lobes. They have a distinctive resting posture, standing high up on their legs with their narrow wings overlapping or rolled up and held at about 90° to the body forming a "T-shaped" profile. Species such as Common Plume Emmelina monodactyla and White Plume Moth Pterophorus pentadactyla will be familiar to many, being relatively common and widely distributed species.

Adaina microdactyla is double-brooded, the adults, which when newly emerged are a pale greenish-yellow colour, can be seen flying from mid May to mid June and again from mid July to late August. It hibernates as a fully-grown larva in the dead, grey-coloured stem of the foodplant, Hemp-agrimony Eupatorium cannabinum, on damp riverbanks and places on the downs, and can be found throughout the winter and early spring. The larva feeds in the upper half of the stem often at or near a leaf or stem node. It eats the living pith during August and September often causing the flowers above the feeding point to abort. In thick stems there is little sign of feeding, but thinner stems form a swelling or gall. When fully grown the larva may overwinter in situ, or move down the stem and form a new gall as a hibernaculum. The overwintering gall will have a 1.5 mm hole in the side partly plugged with a pointed pellet of silk. To confirm the species split open the stem with a thumbnail or knife and the larva will be sitting in a flimsy cocoon across the width of the stem and slightly higher than the hole. The larva is creamy-white with a brown head 6-7 mm long and cigar-shaped. There is a broad but faint dorsal band of dark brownish grey becoming wider towards the head and tail. Keep the stems with larvae in an outhouse, slightly damp, and the larva will pupate when the weather warms up in April and emerge about a month later.

If you find any stands of Hemp-agrimony (maybe when you are out looking for Brown Hairstreak eggs?) spend a bit of time examining the stems for these tell-tale larval feeding signs. If you find anything, please submit the details with some photos to iRecord, or by email to bobforeman@sussexwt.org.uk with details of location, grid reference and date found.