Holborough Marshes

A very pleasant walk around Holborough Marshes, starting off in warm sunshine, getting gradually cooler and just caught by the first start of the rain as we approached the car at 6:30 p.m. Then off to Pam's for lamb champ chops cooked by Paula, with Monty smelling strongly of the marsh ditchwater. Nightingales singing strongly!

In the narrow strip of woodland leading out to the river wall just at the start of the reserve, there were four Speckled Wood, Pararge aegeria, all of them that I saw likely to be males. They were in apparently obvious territories, from ground level to about waist height, and I saw one duel. One was already quite battered, and it seems that each individual adult only survives for approximately one week, perhaps feeding off honeydew up in the canopy. These will have over-wintered as chrysales. There will also be over-wintering caterpillars, an almost unique scenario amongst butterflies to have these two options, which still have to form chrysales and which will then be on the wing from sometime in May in their turn, peaking in June. It was impossible to tell if there were three spots or four spots on the top of the hind-wing in these insects.

This is the same butterfly's head in close-up, demonstrating the irridescent hairs:

While photographing the Speckled Woods, the camera caught the underside of a Greater Celandine leaf, Chelidonium majus, with its long thin silky hairs:

Here are the flowers of the Greater Celandine, with the same silky hairs, this time on the outside of the sepals.

One of the high points was a female Gooden's Nomad Bee, Nomada goodeniana on a Dandelion flowerhead (Taraxacum officinale) - apparently they seem to be seen on these quite often . The lack of any red on the abdomen, the unbroken yellow bar on T2, the yellow tegulae, the yellow tubercules (many on this specimen) all point to this species. The orange antennae have no black on them and have only 12 segments, the eyes are reddish rather than green spotted and the abdomen has only 6 tergites, so this is a female.

In this side view the pattern of yellow bands on the tergites and sternites of the abdomen can be seen, as well as the long mouthparts seeking the pollen or nectar in the capitulum.

A quiet Holborough

Quiet because of a much lower variety of birdsong, but there were some good insects and a couple of really nice songsters.

Butterflies were nice with a fresh Speckled Wood, Pararge aegeria, and two others scrapping, over the brambles on the path in to the reserve by the houses. At the end of the walk there was a Green-veined White and a male Orange Tip along the concrete path.

The picture below shows a Bombus pascuorum doing something quite strange - it is investigating the remnants of an old Lamium album flower from which the corolla has already fallen off. There seems to be little to attract the bumblebee, and little advantage to the flower in attracting the bee. I wondered if this is a common observation?

Well, it turns out apparently that Lamium is unusual in the family Lamiaceae in that the nectaries continue to secrete nectar for some time after the corolla falls off. This seems odd, but after all, why not if it perhaps more successfully facilitates pollination of the other flowers in the whorl, the structures are there anyway and perhaps it just shows common sense to leave them releasing for a day or two longer. This fits in with the often bizarre position of the nectaries in many other plants, by no means confined to the flowers themselves, for example perhaps being on leaves close-by.

The nectaries themselves in Lamiaceae are often are a ring or torus of four individual structures surrounding the four ovary chambers. The fourth is however undeveloped and apparently vestigial in Basil, the three developed ones directed downwards towards the lower corolla lip. In other Lamiaceae there may be only one active lobe, the one with the thickest epidermis. The nectar-producing cells inside the nectaries are small and parenchymatous, with abundant inter-cellular spaces to release the nectar into. Starch acts as the carbohydrate store and builds up in them prior to anthesis, and then disappears as the flower develops and requires the sugary nectar. The stomata on the nectary surfaces are ultimately fed solely by the phloem vessels in some Lamiaceae and are at least in some cases "anomocytic" (lacking in subsidiary cells), perhaps subsidiary cells being unnecessary where close control over opening and closing is unnecessary. However in Lamium oddly enough there are more than two guard cells per nectary stoma!

Fuller details of the fascinating Lamiaceae nectary structure and function can be found in the article in the South African Journal of Botany on Floral nectaries of Basil (Ocimum basilicum): Morphology, anatomy and possible mode of secretion written by M.P. Mačukanović-Jocić, D.V. Rančić, and Z.P. Dajić Stevanović from the University of Belgrade.

This is a more conventional picture of a bee visit, with the anthers held over the back of the bee, releasing the pollen there. Much will be collected by the bees' legs perhaps and transferred to the pollen baskets. Other grains may end up on the stigma of the next flower to be visited.

This individual has quite worn wings so she is probably not fresh. She is quite a large insect judging by the size of the flower she is visiting, so she could be either a Queen from last winter or a large worker from the first generation this year. I am pretty sure she is the standard Carder, B. pascuorum, as she has shaggy hair overall, paler hair on segment 1 of the abdomen than on segment 3, and a few black hairs do appear to be present on the back (and therefore maybe the side?) half way along the abdomen.

This is the same bee having moved on to another, more advanced whorl of flowers. Here, although most of the flowers in the whorl are over, there is at least one more to come! As the bee makes use of one of the flowers on the back of the whorl, you can see how the legs are being used to help hold the bee in position for nectaring, head held deep in the hood of the corolla. There might also be a tiny insect on one of the calyces to the front of the whorl.

Before the Bumblebee got on to that whorl it had been up to a bit of thievery, getting at the nectar by attacking the side of the corolla just above the ovaries:

Holborough birdsong

Cool, breezy and early afternoon at Holborough. I walked through the woodland path out along the sea wall towards the river end of the concrete path, and mainly listened to birdsong,

There were at least one Nightingale, one Chiff-chaff, one Chaffinch, Moorhens, three Sedge Warblers (I think), two Blackbirds. Overall what a wonderful experience! In addition, a Heron and about a dozen Herring Gulls were on the river mud.