Knopper galls on oak

Every single acorn on this young oak tree has been affected by galls.

Knopper galls
Knopper galls

I think that they are knopper galls, caused by the wasp Andricus quercuscalicis’s egg laying. The affected acorns, all of them in this tree’s case, are unable to develop properly or germinate. Instead, they will fall to the floor and next spring female wasps will emerge from them and go looking for Turkey oaks (Quercus cerris): without Turkey oaks, they can’t complete their lifecycle.

knopper galls3

knopper galls 4
The deformed acorns feel slightly sticky and waxy.

There is a fascinating account of the wasps (Andricus quercuscalicis) and their galls on the University of Reading’s biodiversity blog or at Wikipedia.

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Sawfly larvae on birch

These sawfly larvae are making short work of devouring the leaves on this birch sapling.
These sawfly larvae are making short work of devouring the leaves on this birch sapling.
I think these are the larvae of Croesus latipes - I can't find a common name for them. They are considered a minor nuisance, not a serious pest.
I think these are the larvae of Croesus latipes – I can’t find a common name for them. They are considered a minor nuisance, not a serious pest.

The posture the larvae are adopting is characteristic of many sawfly larvae. Also note the way their stubby little prolegs start from segment five (the first three pairs of legs are the proper legs that will remain in the adult, they are on segments one, two and three).

Generally, caterpillars of moths and butterflies have fewer prolegs than sawfly larvae and they start further back than segment five. Have a look at the post about caterpillars on redcurrants for a labelled photo showing the segments, legs and prolegs.

 

Ragwort and the Cinnabar moth

This strikingly coloured moth is the Cinnabar moth. The plant it is on is common ragwort (Senecio jacobaea – which is looking a bit tatty as it has recently been mowed). Ragwort is the principal food plant for the caterpillars of the Cinnabar moth. The caterpillars are equally striking, but they are striped black and yellow.

Cinnabar moth on ragwort
Cinnabar moth on ragwort

In the UK, there are few plants that excite such heated debate as ragwort does. Sadly, the debate is generally more heated than considered.

Ragwort, like very many plants, does contains naturally occurring “toxins”: specifically, pyrrolizidine alkaloids. These alkaloids are produced by vast numbers of plants. The alkaloids make the plants taste bitter and unpalatable, thus deterring herbivores from eating them.

The risk from ragwort comes when it is dried and mixed in with a hay crop – then animals are less able to detect the bitterness and also unable to sort out the different herbage and forage and consequently more likely to ingest ragwort (or any other undesirable plants).

So, ragwort does have some risks, but it also has lots of benefits, including being a food plant for dozens of insects, including several endangered species. It isn’t a plant that warrants a knee-jerk panic reaction, but a considered assessment of its potential risk and benefits in any given situation.

In 2010, the Welsh Government published new guidance on ragwort control. This Code of Practice presents a surprisingly balanced analysis of the ragwort situation, as well as guidance on control strategies as and when appropriate. It is freely available for download from the Welsh Government website.

 

Maybugs play peek-a-boo

Who's peeking out from under the Philadelphus leaves?
Who’s peeking out from under the Philadelphus leaves?
A pair of cockchafers - Melanotha melanotha
A pair of Maybugs or cockchafers – Melanotha melanotha. The one on the right, with the larger antennae is the male.
Unimpressed with being discovered, they make their departure.
Unimpressed with being discovered, they make their departure.

Cockchafers (Melanotha melanotha) have lots of other nick names:  May bugs is probably the commonest – although they’re not a “bug” in the true sense of the word, they’re a beetle.

In some areas, their larvae are an agricultural and horticultural pest.  They live in the soil for several years, munching on plant roots. Here, in north Wales, they are relatively uncommon.

The Natural History Museum and Buglife both have lots of information about cockchafers, including how they (yes, the bugs) were once taken to court in France and ordered to leave the city of Avignon or else be killed!

 

 

 

Capsid bugs on Welsh poppies

Capsid bug (Calocoris sexguttatus) adult and nymph on Welsh poppy (Meconopsis cambrica.
Capsid bug (Calocoris sexguttatus) adult and nymph on Welsh poppy (Meconopsis cambrica.

Welsh poppies are generally trouble free, but these capsid bugs have a particular taste for them. They eat through a feeding tube that they poke into the flowers at bud stage. Their saliva causes the tissue around the hole to toughen, discolour and die. Then, as the flower opens, the wound sites will often tear. Consequently, the flowers are marked with discoloured spots and little holes.

These bug aren’t a major pest or problem, and if possible (as always), it is best to tolerate them.

Golden micro moths

There are more than 1500 species of micro moth in the UK. But it’s quite possible you’ve never noticed them as, like the name suggests, they’re small. These are Micropterix calthella, sometimes called the marsh marigold moth.  Their larvae feed on dead and dying plant material. The adults feed on pollen.

Golden micro moths, Micropterix calthella, feeding on the pollen of a buttercup
Golden micro moths, Micropterix calthella, feeding on the pollen of a buttercup
These moths are swarming over a click beetle.
These moths are swarming over a click beetle.

Eristalis tenax – the drone fly

The larvae of many hover flies are beneficial in the garden, because they feed on aphids. Eristalis tenax, the drone fly, is one of our commonest hover flies, but its larvae aren’t so useful: they are the so-called  “rat tailed maggots”, living in water and feeding on microscopic things they find there.

You might see them sometimes, in a pool, or a forgotten bucket of water, with their “tails” poking up to the surface of the water.

Eristalis tenax - the drone fly

Nevertheless, even if the larvae aren’t particularly useful, the fly itself is still an important pollinator and a very welcome visitor.

Eristalis tenax - the drone fly - on a dandelion
Eristalis tenax – the drone fly – on a dandelion

Dandelions are great for attracting hover flies of many types, so it is worth keeping a few. If you’re worried about seeds, pick the flowers before they turn to seed-clocks and throw them in the bin, or on a fire, don’t put them in the compost heap!