June 2012

May has been a busy month for all living things. Regular cycles of sun and rain have led to vigorous growth of plant life, providing ready and abundant energy resources for the web of trophic levels of animal life. Many birds have fledged early broods already, while some that started too early have not yet been successful – some of our Cirl buntings (Emberiza cirlus) are in this latter category. However, there’s plenty of time yet to catch up. I was delighted to discover the active nest site of a pair of Cirls close to my own home, right at the end of May. I’m now on chick alert, waiting to hear their first calls to parents eager to feed them.

Among the birds already hatched but not yet fledged are our Peregrines at St. Anthony Head. Having emerged early in May, the two chicks are now growing well and are displaying much downy vigour when active, especially when a parent arrives with a kill to feed them. Favourite food prey includes pigeon (Columbidae) species and jackdaws (Corvus monedula). A number of us are keeping watch over the chicks as they grow to maturity, from the bird hide on St Anthony Head. It is very much hoped that the chicks will fledge into beautiful juveniles like the one depicted in the image, which was one of last year’s fledglings from the same location.

Early in the month I came across another, renewed and rare occurrence in my own garden: a tiny stick-insect, about 2½ cm long, clinging to a shrub. There is a growing number of southern England locations where these animals – properly called Phasmids – occur, including here in the Roseland. They became naturalised here and in wider Southern England over 100 years ago, having been brought either as curious pets or on plants imported for the horticultural trade from New Zealand.

The species you are most likely to see here in the Roseland is the Prickly Stick-Insect (Acanthoxyla geisovii), which was discovered spreading out from around St Mawes. It is also found in the Torbay area of Devon and in the Scilly Isles on Tresco and St Mary’s. Roseland individuals are said to be descended from insects collected from Tresco and deliberately released in a garden at St Mawes.

Prickly Stick-Insects are easily identified, especially when large, as the green or brown body is covered black spines. They can grow up to 10cm or more in length. One that I found in my garden a few years ago was approximately this size.

The Unarmed Stick-Insect (Acanthoxyla inermis) occurs in several sites in Cornwall and may also now be present in the Roseland. Clusters of populations occur around Truro, Falmouth Mevagissey. As its name suggests the Unarmed Stick-Insect’s body does not have spines and is fairly smooth. It was probably introduced accidentally to Cornwall through the import of plants for the horticulture trade early in the 20th Century.

What makes stick-insects especially fascinating is their life cycle. All individuals are female and reproduce without males, a process termed parthenogenesis. There are no known occurrences of males, not even in New Zealand where the insects originated. Females produce fertile eggs that hatch in spring, revealing miniature stick-insects just over 1cm long. They will grow quickly to maturity and then begin egg production. Eggs are simply passed and fall to the ground, to await emergence of the juvenile insects in the following spring. Adults are short-lived and unlikely to survive winter naturally.

Despite being an introduced species, stick-insects do not seem to pose any threat to our indigenous plant or insect life. Their preferred foodplant is the ubiquitous bramble, although their diet is adaptable and varied.

Some things to do for Roseland nature in June

· Have you seen naturalised stick-insects in your garden? The UK Phasmid Study Group want to hear from you! They’re keen to hear about any new sightings, so add your records here. They also have an upcoming Summer meeting event being held at the Natural History Museum in London, at 11:30 on 7th July.
· Keep your eyes peeled for deer (Cervidae)! Despite being massively under-recorded in the Roseland, there is plenty of anecdotal evidence that several species of deer live in the region. A recent sighting by a local hunting specialist suggests that the Japanese Sika deer (Cervus Nippon) are now living in the Roseland. However, Sika and UK mainland red deer are able to interbreed, producing viable offspring. This is making it difficult to separate the species for the purposes of recording.

Did you know that ‘Sika’ is Japanese for ‘deer’? So our anglicised name for this species is Deer Deer…!

References

Phasmid Study Group (2012) Phasmids: An Introduction to the Stick Insects and Leaf Insects. Online. Available from:
http://phasmid-study-group.org/content/Phasmids-Introduction-Stick-Insects-and-Leaf-Insects.

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