Monday, 12 July 2010

Phasmid Study Group summer meeting

On Saturday I went up to the Phasmid Study Group summer meeting at the Natural History Museum in London. The PSG is one of the older specialist invertebrate study groups in the world, and has a wide membership from professional entomologists to children (some of whom came to the meeting).

Phasmids (variously called stick insects or walking sticks) are a very widespread group, occurring on all continents and in most climates. There are no native British species, but at least three New Zealand species have been established in the UK for nearly 100 years. In warmer climates they are a potential pest, so in the US especially keepers may face restrictions on whether they can keep them, depending on the local climate and agriculture. Despite their potential for producing large numbers of offspring, in the UK at least they are an apparently harmless addition to the British insect fauna.

The closest living relatives of phasmids are probably the grasshoppers, with which they share a tendency for extravagant camouflage. The phasmids walk rather than jump, but many species can fly, especially the males, in a rather grasshopper-like flight. Unlike the grasshoppers, they are almost entirely nocturnal, remaining still by day and only awaking to feed at night.

All known phasmids eat plants, in many cases only a few specific types. Some are more generalist feeders, and many species can be maintained in captivity on commonly available plants such as Blackberry, Oak, Privet or Eucalyptus. In most cases husbandry is simple, with the foodplant supplied in ajar of water and the animals sprayed lightly once or twice a day to maintain humidity. Depending on the native habitat, heating may or may not be required, but good ventilation is beneficial providing the humidity does not drop below the individual species requirements.

The Saturday meeting went well, with some beautiful high-resolution photographs of phasmid eggs (these are as distinctive as the adult insects and much used in identification), and a slide show of a collecting expedition to Malaysia. Because of their camouflage, phasmids are hard to study in the wild and it is very probable that there are many more species to be described. In many cases as well, only one gender is known, and the nymphal stages are unrecorded. Even less is known of their ecology – with most species only habitat descriptions and the time of year that adults are seen is the most that anyone has recorded (if that).

The highlight of the day though is the livestock exchange at the end of the meeting. Many hobbyists bring surplus stock to be distributed, and anyone who is interested can take a new species home. As phasmids are often colourful or fascinatingly formed, and in some cases very variable (Phencephorus cornucervi varies the degree of bracket fungus mimicking outgrowths depending on humidity for example) there can be some demand for the rarer species. As usual, I came home with some new species to raise. My current collection comprises the following:

Peruphasma schultei

I have kept these for several years. They are easy to keep and breed at room temperature on Privet. A fairly new species in culture (the species was only described in 2005); they have become very popular very quickly. They originate from Peru, from the Cordillera del Condor. This is the species shown at the top of the post.

Oreophoetes peruana

Another Peruvian species, this is unusual in feeding on fern (most phasmids feed on various angiosperms). Like the previous species, they are warningly coloured in either green and yellow or red and black, making them very striking display animals. I got some nymphs at the meeting – I have kept them before but not managed to raise a new generation, probably because the eggs were too dry. Hopefully with these I will have more success.

Haaniella dehaani

These originate from Malaysia. A terrestrial species, they feed on Blackberry and require fairly high humidity. They bury their eggs in the substrate, so they need to have about 3cm of peat on the floor of the cage to lay in. I have one pair of adults. They have laid eggs, but none have hatched yet - phasmid eggs can take many months to emerge.

Clonaria conformans

These originate from Vietnam. A fairly standard species, they feed on Blackberry and are easy to keep.

Eurycantha coriacea

One of several species of Eurycantha originating from New Guinea, the nymphs I obtained are from a parthenogenetic all female strain. Parthenogenesis is widespread in Phasmids, but in species with both sexually reproducing and parthenogenetic strains the latter is usually smaller. In Eurycantha some species are gigantic – there were set specimens of female E.ponderosa on show at the meeting which were nearly 20cm long and 3cm wide. Eurycantha are very adaptable in their diet, feeding on Blackberry, rose, and Ivy amongst others. They need similar conditions to the Haaniella to do well.

Medauroidea extradentata

Another fairly standard-looking Vietnamese species, they feed on Blackberry

Diapherodes gigantea

Originating from Puerto Rico and nearby islands, these spectacular phasmids can be raised on Blackberry or Eucalyptus. Watch a video of one here:

Acanthomenexenus polyacanthus

Another Malaysian species, their name comes from the multiple spines that cover their bodies. They are not very large, and can be fed on Blackberry.

This is just a short list of the species in culture – the PSG list has several hundred species in all.

As phasmids are such spectacular insects, they are commonly seen in insect houses at zoos around the world, with several to be seen at Bristol. Even so, only one species is currently the subject of a conservation programme – the Lord Howe Island Stick Insect Dryococelus australis. This was believed extinct for many years, until a tiny population was rediscovered on an offshore island. It is currently being bred in captivity in Australia in  the hope it can be reintroduced to its original home once the rats that caused its near-extinction have been eliminated.

For more information on phasmids, see the Phasmid Study Group website (link on right)

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