Arthropedia - What To Look For In Spring: Sallow

The last forays I made to my local patch (before lockdown) were to check out the sallow flowers.

Sallow is the name given to certain species of willow, notably Goat (Salix caprea) and Grey (Salix cinerea) Willows, which have short erect catkins. Male and female flowers are borne on separate trees with the male ones being the classic well-known pussy willow catkins. Depending on the year, they can come into flower from as early as late February but March is probably the best month here in Norfolk. A good sized tree can have flowers open over several weeks, lasting into April. This early blossoming makes them an important source of nectar and pollen for all sorts of insects. Plenty of flies are attracted to the flowers as well as bumble and solitary bees and also butterflies.

A small straggly sallow in my local cemetery.

The fluffy yellow catkins are the male flowers, chock full of pollen. The female flowers are green and a bit spiky looking, although soft to the touch. They also attract insects by producing lots of nectar. The male flowers attract lots of female and worker bees as they collect the protein-rich pollen to rear their young on. Male bees visit for the sugary nectar that gives them energy to fly around searching for a mate. (Female bees also drink nectar for energy). Most other insects will be after nectar too. The less showy female flowers produce nectar in order to attract insects that have previously visited male flowers so hopefully have some pollen to transfer and fertilise the plant. I’ve always seen more insects on the male flowers than the females.

Classic pussy-willow catkins at various stages of opening.

Because of the bonanza of insects, a good stand of sallows will attract various birds including tits and warblers. One cold spring at Rye Harbour was particularly memorable for me as a fall of warblers included several Lesser Whitethroats that were feasting on the bumblebees high up in the branches of a group of willows. It was also memorable for some forlorn looking Cuckoos sitting hunched up on the shingle amidst the Sea Kale plants in the freezing cold blast of an icy wind!

Field sketches of Lesser Whitethroat at Rye Harbour from May 2013, a particularly cold, late spring.

Field sketches of a Cuckoo at Rye Harbour, from May 2013.

Bees

Bumblebees are regularly seen at sallow blossom, the queens feeding up on nectar when they first emerge from winter hibernation and then the first worker bumblebees collecting pollen to take back to the nest.

*Bombus hypnorum* worker with yellow pollen collected on its hind legs

*Bombus pratorum* queen. Note the reddish tail and shaggy hair compared to *B. terrestris*.

Honeybees also exploit sallows. On a warm windless spring day a stand of sallows will positively hum with busy bee activity as dozens of them collect pollen to take back to their hive. The real stars of the sallows however are the solitary bees. Many of the Andrena species are on the wing early in the year (several are double brooded with a second generation flying in the summer) and will collect pollen from sallows. Several of these mining bees are known to collect willow pollen almost exclusively, making these trees extremely important to their survival.

Female *Andrena bicolor*, one of the earliest mining bees, and relatively small in size.

*Andrena bimaculata* female. These bees are quite variable with some, like this one, having reddish patches at the base of the abdomen whereas others are totally dark.

Female *Andrena nigroaenea* with bright yellow pollen load on her hind legs.

A freshly emerged female *Andrena nitida* getting stuck in to reach the nectar at the base of the stamens. The obvious grey patches on the sides of the abdomen are distinctive and give rise to the English name Grey-patched Mining Bee.

Female *Andrena minutula*, one of the ‘mini-miners’.

Female *Andrena fulva*. The bright foxy red thorax and abdomen make this species readily identifiable even when it is high up in a sallow.

This worker honeybee (*Apis mellifera*) is clinging on to a leaf with her mandibles while she shuffles pollen off her underside with her middle legs onto the pollen collecting areas on her hind legs.

Butterflies and moths

Sallows are a great place to seek out spring butterflies with Peacock and Comma often visiting them and occasionally Brimstones as well. These species all over-winter as adults and will emerge on the earliest of warm days in spring. In mild winters I have recorded butterflies in January and February but in colder years have had to wait until March and occasionally even April for my first sighting. Emerging so early, they are reliant on good sources of nectar. As well as sallows, Dandelions are also very important for these spring flying species.

Several early flying species of moth are known to visit sallows for nectar too. ‘Sallowing’ was recommended for moth enthusiasts in the Amateur Entomologist’s Society‘s publications – going out on a mild windless night and checking sallow blossom by torch light for moths. I tried this once many years ago but without success – the only nearby accessible sallows were beside the river and adjacent to street lights. My nearest sallows now are in the local cemetery, safely locked up at night away from the prying eyes of entomologists!

Interestingly, a number of moths are called Sallows. However, they fly late in the year and are not especially associated with Sallows (although the caterpillars of at least two of them will feed on the buds and leaves, as well as other deciduous trees). As most of them are varying shades of yellow, they are presumably named after their colour rather than any association with Sallows. Sallow can mean “of unhealthy yellow or pale brown colour” but Sallow moths are actually very pretty and two are featured on Plate X in my book “Arthropedia: An Illustrated Alphabet of Invertebrates“.

Hoverflies

Several early species of hoverfly are routinely only seen at sallow blossom, possibly because recorders only look for them at sallow catkins! Some of the Eristalis species over-winter as adults so can be on the wing very early in the year on warm, sunny days although they are at their most abundant in summer when they can be found on the umbels of members of the carrot family (Apiaceae, formerly Umbelliferae).

Female *Eristalis tenax*. A honeybee mimic and one of the commoner and widespread species of hoverfly.

*Melangyna lasiopthalma* is an early spring species that benefits from sallow blossom.

Male *Syrphus torvus*. There are several species in this genus of fairly large, boldly marked hoverflies. *S. torvus* is distinguished from the others by having hairy eyes, most noticeable in the males.

*Criorhina rannunculi* is a real spring gem and is often encountered foraging on sallows, although other early blossom such as Blackthorn is used. They are large hoverflies, being bumblebee mimics and do actually fly with an audible buzzing drone. They vary in colour with red-tailed and white-tailed forms. They are often high up in sallows but I luckily found this one at the base of a moss covered tree.

Other Flies

Flies are on the wing on colder days than many other insects and sometimes they are all I find on sallows. Many of them are small and rather undistinguished so I have yet to identify them (notably the many Anthomyiidae species). ‘Nicer’ specimens turn up though, if you take the time to look for them.