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Six-legged mammoths

I usually don’t keep lists of “must-see” things when going on trips overseas, because past experiences have taught me that the best discoveries come when you least expect them. However, I must confess that I broke my rule before I taking the flight to New Zealand, and I decided that there are three NZ native animals I would like to see in the wild. The first one was undoubtedly the tusked weta.

Tusked weta belong to family Anostostomatidae. These creatures look like they were designed by Hollywood film industry (and yes, I can’t believe I am saying this about an insect): Males posses curved elephant-like tusks that extend forward from their mandibles. The tusks are used to push a male opponent during fighting over females or territories. The females have standard mandibles and do no have protruding tusks.

“Minor” male of Raukumara tusked weta (Motuweta riparia)

Female Raukumara tusked weta (Motuweta riparia)

There are three species of tusked weta in New Zealand:

The Mercury Island tusked weta, Motuweta isolata, is the biggest species of the tusked weta group, with a body length of 80-100mm and a weight of up to 28g. They are extremely rare and have a limited distribution in Middle Island in the Mercury Islands group. Like other native NZ invertebrates, human-introduced rodents are the greatest threat to these insects. The Mercury Island tusked weta is a protected species and a captive breeding and reintroduction program was developed by Department of Conservation in order to introduce this species into other islands in the Mercury group. The Northland tusked weta, Anisoura nicobarica, was once considered a species of ground weta because of its small size (up to 20mm long). It is relatively common throught its distribution range in the far north of New Zealand North Island, occupying cavities in trees similarly to tree weta.

The third species and the one I was after is the Raukumara tusked weta, Motuweta riparia, a moderate-sized weta in comparison to the other two species, with a body length of 30-40mm. It was the most recent one to be discovered, only in 1996. It is found along the banks of forested, slow-flowing streams in Raukumara Range, East Cape of the North Island.

Typical habitat of Raukumara tusked weta – forested, second order streams in the Raukumara range.

Male Raukumara tusked weta (Motuweta riparia)

Tusked weta are nocturnal. During the day they hide under stones in a wide chamber made from silt. The juvenile weta are very common in the habitat and can be easily found even during the day while resting in their burrows. However, the tusks are fully developed only in adult weta, and they are much harder to find by day (although not impossible). They appear to prefer to come out on dark moonless nights when conditions are moist and humid, and climb on the vegetation. Because of their small body size and lack of tusks, the juvenile tusked weta can easily be mistaken for ground weta. However, small morphological differences give them away – mainly the number of spines on the legs but a more useful character is the presence of tympani (the insect equivalent of ears) on the forelegs. These “ears” are missing on the forelegs of ground weta.

Juvenile Raukumara tusked weta (Motuweta riparia)

The adults seem to spend more time on branches and on the ground than on leaves in comparison to the juveniles. Interestingly, there is variation in the length of tusks in males, and “minor” adult males can also be found. These weta are mainly carnivorous, feeding on worms and insects. They are long lived, completing their development from juvenile to adult in two-three years. When disturbed, they immediately jump into the water and after swimming a short distance they press their body against the rocky bottom of the stream. Under running water, they are practically invisible for predators. The weta can stay in this state, completely submerged, for several minutes, after which they poke their heads and first thoracic segment out of the water, trying to assess if the danger has passed. I loved watching them swimming in the water, however it is not the safest place for escaping predators: one of the females I photographed decided to walk towards a small waterfall and vanished between the rocks. After a split second I heard a slurping sound and saw her crawling back up. An eel was lurking in the water below and tried to grab the weta!

Male Raukumara tusked weta (Motuweta riparia)

Photographically speaking, the tusked weta are insects that you love to hate. At night, they usually stand in the most awkward angles and will not move (unless you want to try to make them move and risk the diving of your beautiful weta). By day, they just never stop running, and their dark shaded habitat makes it unusually challenging to capture a crisp photo. I was lucky to have a piece of white paper lying around to use as a background. All in all, I am very glad I saw these marvelous insects, shaped by years of natural and sexual selection. They truly are a wonder of nature.

Why sometimes it is important to remember small details from your childhood

One of the things I intend to write about every once in a while is the use of insects in art or popular culture. I am still not sure if these will be independent posts or inserts within other posts. I thought I would start by talking about keeping insects as pets or insects drawn in Japanese manga and anime, but this week while walking atop one of the hills at Otago Peninsula, New Zealand, I was inspired to write about something more personal.

When I was 10, I used to collect stamps. This hobby was largely encouraged by my grandfather, who was a serious stamp collector. I remember how just by looking in his albums at stamps from all over the world I sometimes imagined myself drifting away to a far away places. I could stare at them forever, and I also enjoyed the smell of old paper. Despite my grandfather attempts to infect me with his obsession, collecting any stamp from just about anywhere in the world was not very interesting for me. I decided to collect stamps of animals and plants only, but my favorite ones were insect-themed stamps, and I had many of them.
Among the first stamps I got were two that I found especially peculiar. They depicted butterflies and came from New Zealand. I remember them very well – they were probably very common because I had dozens of them. But the reason I was intrigued by them is because something about the butterflies looked a bit off. I knew that one of them looked like Vanessa atalanta in a way (I was able to read English at the time, but I did not know what a red admiral is), the wing pattern seemed wrong though, especially for the hind wings. And the art looked, well, a bit like cubism.

This week, over 20 years later, I got my answer.
While I was starting to make my way down hill, I caught a glimpse of some bright red color from a nearby gorse bush. I went closer, and the butterfly took off. Still, it did look like a red admiral during flight, and knowing the territorial nature of this species, I decided to wait. And lo and behold, a few seconds later the butterfly returned to the exact same spot, only this time it landed on a rock.

Vanessa gonerilla, New Zealand red admiral

Vanessa atalanta, red admiral (photographed in Canada)

Now I could take a good look at it. Yes, definitely the same butterfly from the stamp, and the wing pattern fits perfectly. New Zealand red admiral, Vanessa gonerilla. Obviously this is a different species from V. atalanta that occurs in Europe and North America, but the similarity between the two species is striking, both in upper and lower sides of the wings.

Vanessa gonerilla, New Zealand red admiral

Vanessa atalanta, red admiral (photographed in Israel)

While the upper side has the same type of contrasty combination of aposematic coloration – black, white and red (probably to deter predators), the lower side is an explosion of colors (especially in V. gonerilla), and is used mainly for camouflage.

Vanessa gonerilla, detail of lower side. Click for full size.

The red admirals belong to the butterfly family Nymphalidae, and it is a good opportunity to mention that members of this family look like they have four legs only (instead of six legs like all other insects. See photos above). But a close inspection reveals that the adult butterflies do have six legs. The forelegs are shortened and hairy, and held close to the body. They are used for cleaning the butterfly’s antennae from pollen and sometimes even for tasting nectar.

Portrait of Vanessa gonerilla, showing the specialized forelegs for cleaning antennae. They also have hairy eyes, how cute!

By the way, similarly to the European and North American red admiral, the caterpillars of the New Zealand red admiral feed on nettle. The endemic nettle, Urtica ferox, also known as ongaonga, is a large stiff bush (can reach a few meters in height), covered with large stinging spines that remind me of the NYC skyline. I hear these plants are something you want to avoid at all cost, and they sound as bad as the nasty Urtica pilulifera I know from Israel. There was even one case of death caused by this plant (a similar event is reported here).

Urtica ferox (ongaonga). Insert: I see a row of Chrysler Buildings, I don’t know about you.

By the way, I also got to see the tussock butterfly depicted in the second stamp during my first visit to Otago Peninsula a month ago. They were very abundant, flying slowly between the grasses. Unfortunately, by the time I arrived to the site the second time, they were all gone. It was nice to revive a piece of my childhood while visiting a foreign country many years later. Sometimes you have to go halfway around the world to come full circle.

Leaf-veined slugs

In one of my day walks through the forest I reached down to dismantle a rotting piece of wood, to reveal some of the invertebrates that are hidden within.

Does not look like a slug at first glance.

There are about 30 species of native New Zealand slugs, most of which are endemic to New Zealand. All have a characteristic leaf-vein pattern on their dorsal side, most likely for camouflage. This leaf-vein pattern is absent in introduced species. In addition, native leaf-veined slugs have only one pair of tentacles – unlike introduced species of slugs, which have two.

New Zealand slugs belong to the family Athoracophoridae. The one in the photo below belongs to the genus Pseudaneitea. The pale bumps on the surface of the dorsal side are called papillae. In some recently discovered species the papillae form retractable spikes. Very cool, however it is unclear what the spikes are used for.

Leaf-veined slug (Pseudaneitea schauinslandi)

More common are members of the genus Athoracophorus. Leaf-veined slug biology is poorly known, but they are thought to feed mainly on algae and fungi found on the surface of plants. In contrast to other slugs, these beauties do not feed directly on plants’ foliage, and therefore do not cause excessive damage to plants. I wonder if they are ever considered as plant pests.

Leaf-veined slug (Athoracophorus bitentaculatus) with body fully extended

Leaf-veined slug (Athoracophorus bitentaculatus) with body retracted

Leaf-veined slug (Athoracophorus bitentaculatus). They are just so adorable.

The slugs are nocturnal, and frequently can be seen mating on the surface of leaves. All terrestrial slugs and snails are hermaphrodites meaning they have both male and female reproductive organs, but they need to mate in order to fertilize each other’s eggs. Most slugs have an enchanting mating ritual, in which they hang down on a rope of mucus and encircle each other until they form a spiral with their bodies. Their reproductive organs are drawn and get entangled too, until eventually flattening, creating a translucent flower-like structure. The mating process in leaf-veined slugs seems a little less “exciting”. The two mates meet on the surface of a leaf or on a thick branch, and after a short period of time spent familiarizing with each other, they exchange sperm. In the photo below the male reproductive organ is visible (a slug’s genitalia is located close to the head), and these slugs are in the process of exchanging sperm. Once the exchange is completed, the slugs part and each one lays clutches of soft eggs in a moist protected place, such as under fallen leaves or in rotting logs.

Leaf-veined slug love (Athoracophorus antipodarum)

Don’t mess with the Huhu

On my first night in New Zealand, I did something that I always do when I get to a new place – see which insects were attracted to light that was left on. The usual suspects are various species of moths, but sometimes also katydids, antlions and beetles.

To my surprise, the first insect that I found was a large longhorn beetle (family Cerambycidae). With a length of 50mm, hairy body, large mandibles and beautiful elytra reticulated in yellow, one could not miss it resting on the asphalt. I later learned that this was the huhu beetle, Prionoplus reticularis, New Zealand’s largest endemic beetle.

The huhu beetle, Prionoplus reticularis

Detail of Prionoplus reticularis elytra

Portrait of Prionoplus reticularis

The adult huhu beetles do not feed and live for about two weeks only. These insects spend most of their lives in the larval stage, boring into and feeding on dead wood. They can become pests in sawn timber and logs, eventually destroying the wood and leaving just the outer shell. The larvae are considered delectable wild food and were traditionally harvested by the Māori people to be eaten raw or cooked (note to self: I need to try this). At the end of their growth the larvae reach an impressive body length of 70mm and create a chamber for pupation. The adult beetle emerges from the pupa after 25 days and uses its strong mandibles to break free from the pupation chamber in the wood. The whole life cycle can take up to several years.

The adult beetles appear during the southern hemisphere spring and summer (November to March). They start their activity around dusk, and many of them reach outdoor lights and well-lit rooms in their heavy flight. I often found mating pairs in close proximity to light bulbs.

Many people fear these beetles for no good reason (or worse – I heard people relate to these beetles as cockroaches). The adults look a bit scary with their enormous jaws and long antennae swinging from side to side as they walk, but they are harmless and not aggressive. Well, that is, if they are not provoked. They can still use their mandibles to bite, but their bite is a lot less serious than other bites I got while in NZ (for example, ground weta’s. Stay tuned!).

Huhu beetle (Prionoplus reticularis). He’s coming to getcha!

NZ Forest critters – first impressions

The insects I am currently after in NZ are nocturnal (meaning they are active at night) – this ensures me some interesting encounters with animals that are usually shy and cryptic. I thought I would start by describing to you my few readers (most likely my friends, family, and if I am lucky maybe one or two of my former students) what my night activities are like at the moment.
So what kind of animals you can find while taking a night walk in the forest?
Surprisingly for me, the most common animal to encounter in the NZ forest during the night is not a cricket or spider, but representatives of a genus of cockroach. These relatively small cockroaches (15mm) belong to the genus Celatoblatta of which 16 species are known. Very similar in appearance to the northern hemisphere German cockroach, they occupy the leaf litter and low forest plants. I mainly found them on ferns, and although I cannot tell them apart, I am certain that I saw more than one species.

Forest cockroach (Celatoblatta sp.)

Another common insect active in the dark forest is the crane fly. Here too, several species are seen, but I am talking about a particular species. One that is so massive, especially during flight with its thick leathery wings, that often I was not really sure what I was looking at. Unfortunately I have no idea about the species name.

Crane fly (unidentified)

Slugs are also seen frequently, usually climbing on tree trunks, on logs and sometimes on leaves (lower left). The slugs I have seen so far are very different from the ones I know, and I will dedicate a separate post for them. Ground weta (genus Hemiadnrus, lower right) are common on tree trunks and low plants. A very interesting insect group and the core of my current study – they will receive more attention in future posts.

Leaf-veined slug (Athoracophorus antipodarum)

Ground weta (Hemiandrus “onokis”) nymph

I will end this post with two creatures that are not as common as the ones above, but can be easily found with a little patience.

Antlions (order Neuroptera) are sometimes seen on the vegetation. This pair was sitting on a branch and were probably communicating using their antennae. It is a relatively large species, so at first I thought they belong to the family Myrmeleontidae. However, looking at their antennae, I see that they are simple and not curved as in Myrmeleontid antlions. Therefore I am guessing that these are big lacewings, but I am still not sure regarding the family or genus.

A pair of antlions (unidentified)

If you are lucky, you might stumble upon cicada larvae as they emerge from the soil and climb nearby objects to molt for the last time into adult cicadas. I was fortunate enough to see this beautiful individual drying its wings after molting. It belongs to the highly diverse genus Kikihia, with about 30 species. Unfortunately, further identification is very difficult because there is no identification key available to the species level. This is one of the most beautiful insects I have seen. Vivid green in color with red “socks”, and rows of golden hairs on the abdomen.

A newly emerged cicada, Kikihia sp., with the moon shining in the background

In New Zealand!

For the past three weeks or so I have been traveling in New Zealand, looking for suitable fieldwork sites for selected species of ground weta. It is now summer at its peak in NZ, the air is (usually) warm and the sun is scorching hot. This is quite a change from the frozen cold state I left Canada in. Although I enjoy the scenery and the lively creatures I encounter, I have to admit I was never a summer person. I prefer the cold temperatures, so in a way I miss the winter. However, I am aware that had I been in Canada now I would have wished for some warm sunny days. Got to take whatever I can.

Meanwhile, in Canada…

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Entomologist and Photographer