Seeing is Believing

The Canterbury tree wētā (Hemideina femorata) is endemic to the lowland forests of Canterbury. Like other tree wētā, it is a sizeable insect and an opportunist when it comes to food, eating mostly leaves, but taking advantage of the protein in other insects it encounters.

Here in rural Canterbury, it’s rare to find tree wētā. Old timers talk about how you used to see wētā every time you trimmed the hedge, but in 15 years of trimming, I have seen no wētā. I’ve even put wētā houses (like bird houses, but designed to appeal to wētā) in the hedge, but have never found anything but spiders in them. 

Though I’ve never seen a study of their population changes, anecdotal evidence indicates Canterbury tree wētā numbers have dwindled with the intensification of agriculture and the increased use of chemical pesticides.

I have been fortunate to raise quite a few wētā in captivity, and in doing so, I’ve become familiar with the insects’ strong smell. This smell has been their downfall when faced with introduced mammalian predators—strong enough for even a human’s nose to perceive, it acts as a beacon to hungry rats, and stoats.

But it’s not just in my insect tanks I’ve smelled tree wētā. With some regularity in the early morning I can smell them in the hedge when I pass on my way to feed the chooks.

We humans have a poor sense of smell, as mammals go. We rely much more heavily on our sense of sight for identifying things. So for years now, I’ve doubted my nose, because I’ve never seen a wētā on the property or anywhere nearby.

But not long ago, on an evening walk with my husband, we found an adult tree wētā dead on the road.

Yes! I knew my nose couldn’t be deceiving me, though I was never confident enough to declare their presence based on smell alone. Now I am. I may not have seen them in my hedge, but if there are wētā being hit on the road a hundred metres from my house, I am willing to believe my wētā-scented hedge harbours them too.

A Day Off

Cathedral of red beech

Sunday dawned warm and sunny, and I prepared myself for another day of hard work in the garden, in spite of my aching back. It would be a crunch to finish what I needed to stay on track—my garden to-do lists get longer each week, and I don’t dare fall behind at this time of year.

Meanwhile, my husband was fretting about the lectures he still needed to prepare for this week. But he’s much better at relaxation than I am. Before I had a chance to gather my tools, he suggested a hike instead of a day of work.

So we ignored our pesky to-do lists and enjoyed a day at Hinewai. 

Hinewai Reserve is privately owned, and encompasses 1250 hectares of the outer Banks Peninsula. It includes a glorious mix of vegetation types.

The track forms an avenue within a dense kānuka stand.

Probably the most impressive are the 50 hectares of old growth forest. The red beech create a green cathedral, shading out much of the undergrowth. The effect is in stark contrast to the dense kānuka stands that blanket other parts of the reserve.

At this time of year, the gorse is in full bloom. Management at Hinewai allows this invasive weed to grow, because it provides an effective nursery for native trees. Eventually, the native plants will overtop the gorse and shade it out, but in areas recently disturbed by fire, the gorse is thick. On Sunday, the tops of the hills looked like they’d been capped with bright yellow snow, for all the gorse.

Gorse in full bloom in a recently burned area.

With 330 species of native vascular plants, and 60 species of fern (including six species of tree fern), Hinewai is probably the most diverse site on the Banks Peninsula. We never fail to see interesting things when we visit. This visit was no exception. A bright purple fungus creeping along a rotting branch was probably the most unusual find on Sunday, but we were treated to tree fuchsia in bloom, kererū swooping overhead, and pīwakawaka and tomtits flitting around among leafy lacebarks, kahikatea, tōtara, and kōwhai. I enjoyed seeing my favourite filmy ferns, with their translucent fronds. Large quantities of ongaonga (tree nettle) supported the red admiral butterflies that were enjoying the warm day along with us, flitting through the dappled light in the forest.

View down to Otanerito/Long Bay

And, of course, as with most spots on the Banks Peninsula, the views from the clearings at Hinewai were spectacular. 

My weekend to-do list forgotten, I had a lovely day enjoying the outdoors. Next weekend’s list is necessarily longer now, but it was good to take a day off. I must remember to do that more often.

 

Skink Snap

Stepping out the door one day last week, I met with this lovely skink on the porch. It’s not unusual to see them on our property, but it is unusual for them to sit still for photographs. The cool morning must have made this one sluggish, because he happily waited while I snapped a few pictures. 

I’m always pleased to see skinks; native vertebrates are pretty rare out here in the middle of the Canterbury Plains. We’ve deliberately landscaped to protect and encourage skinks, as I’ve blogged about before. It’s nice to know our efforts have been successful. On sunny days the native plantings rustle with unseen skinks, and the rocks sport basking lizards. I’ve learned not to leave garden hoses lying on the ground, lest a lizard take up residence in the open end.

The common skinks in our yard aren’t in any danger of extinction (unlike many of our native lizards, which are), but it’s nice to know they thrive here. Seeing them makes me smile.

Mingha-Deception Track

Last Wednesday was a glorious, chilly, sun-sparkling autumn day. A perfect day to climb up over the main divide on the Mingha-Deception Track. The track starts where the Mingha River joins the Bealey River. It follows the Mingha upstream through beech forests to the tussock-covered Goat Pass. On the way, it passes a spectacular hanging valley over which tumbles Kennedy Falls—150 metres tall. Kennedy Falls reminds me of one of the reasons New Zealand is so special. This spectacular natural feature sports no access road, no interpretive signage, no gift shop, not so much as a footpath to reach it. It spills down the mountainside in all its glory, unsullied by tourism. By the time you get to view the falls, you feel you’ve earned the privilege.

Goat Pass Hut, set in a hollow just north of the pass, is a spacious hut which we shared with just one other group of trampers Wednesday night. As we ate dinner, a group of noisy kea flew overhead. Thankfully, they didn’t call in at the hut to tear apart our shoes drying on the porch. About ten-thirty, while we all lay snug in our sleeping bags, great-spotted kiwi began calling around the hut—males and females duetting and answering one another. The great-spotted kiwi is a nationally vulnerable species, with a population around 15,000, and I always feel lucky to hear them in the wild.

Thursday morning saw us scrambling down the boulder-strewn upper Deception River on the other side of the main divide. 

Formerly known as Goat Creek, the Deception River got its name in 1900 when surveyor Mr. N. A. Harrop warned engineers building the rail line along the Otira River that the water level in the little river was deceptive—they had no idea how much water could come down the river where it flowed into the Otira River. Three months later, the river flooded and crossed the Otira Valley, damaging the new rail line. It has been called the Deception River ever since.

The day we scrambled down the Deception was one of those deceptive days—the river was lively and powerful, but the water was clear and low enough to cross on foot. Tumbled and scoured boulders left no question about what the river could be like, however. It’s not a place you’d want to be in a storm.

A few hours downstream, we passed a pair of whio (blue ducks) sitting on the rocks preening and ignoring us. Like kea and kiwi, whio are threatened with extinction. There are fewer than 3,000 remaining, so seeing a pair of them was a treat. 

The Deception Valley is narrow and steep, with many side streams pouring into the river, often in waterfalls that would be tourist attractions in their own right if they were anywhere else. Old slips, scoured into crumbling cliffs by the river, speak of a landscape in constant motion. A section of the river smells of sulphur from warm springs nearby—a reminder of the intense geological forces that have shaped the land.

As we emerged from the valley onto the wide flat where the Deception meets the Otira river, the deceptive nature of the river revealed itself again. Freshly tumbled rocks lay in drifts on the forest floor, far from the river’s current flow, showing the extent of recent flooding.

We had a glorious two days, with perfect weather, great wildlife encounters, and good company. Definitely a track to recommend.

Beach Hangout

We nipped out to the beach after dinner on Saturday. We had a nice walk on our lovely, lonely bit of coastline.

But the beach was busy with youth hanging out (up to no good, probably). Some were alone, and some were in groups, strutting their stuff.

But these youth weren’t your usual crowd of city kids, they were juvenile spotted shags, Strictocarbo punctatus punctatus, also known as spotted cormorants, parekareka, and kawau tikitiki.

Shags were once heavily persecuted as pests. Fisherman believed they destroyed the fisheries, snapping up all the commercial fish and decimating their numbers. Research has shown, however, that their impact on fisheries is minimal. On the other hand, there is some evidence that, in our area at least, shag populations are hurt by commercial fishing. Spotted shag populations on the Banks Peninsula rose from 9,787 pairs in 1960 to 22,123 pairs in 1996 following a reduction in commercial fishing around the peninsula. Illegal shooting can also cause local population declines.

The spotted shag is a marine species, never venturing far from the sea and feeding in deep water up to 16 km from shore. They’re gregarious, breeding and roosting in colonies with up to 2000 birds. The groups of juveniles on our beach were small—a few dozen birds at most. These birds were probably born on cliffs around the Banks Paninsula, and when mature, they’ll head back to those cliffs to lay eggs and rear their young.

So they really were just hanging out on the beach, just like teenagers from Christchurch hang out on the beach on weekends, away from the adults, goofing off and getting takeaways.

Mystery Maggots

Caterpillar, not maggot–see the six true legs and 10 prolegs?

The weather has been hot here, and all the doors and windows stand open all day. With no window screens, that means an array of bugs (and the occasional bird) pops in and out of the house. It’s not unusual to find flies, butterflies, damselflies, etc. on the windows. 

Still, I did a double-take when I saw maggots on my desk the other day. I knew they hadn’t flown in on their own—they must have been hatched nearby. I checked for unseen dead things on the shelves above, but found nothing. There was another maggot this morning, and I did a second unsuccessful check for the source. Then, while I was away from my desk for fifteen minutes, another appeared.

This time I pulled out the microscope and had a closer look.

It wasn’t a maggot at all. It was a tiny caterpillar.

I could think of no reason for a bunch of caterpillars to be living on my bookshelves and dropping onto my desk.

Then I remembered earlier in the day I’d shooed a wasp out of the office several times.

Bingo!

The wasp was a European tube wasp. These little insects seek out cracks and holes to nest in. They fill their nests with up to 20 caterpillars as food for their larvae and then seal the nest with mud.

That would explain the bits of dried soil that accompanied some of the ‘maggots’.

We’ve seen the same thing with our native potter wasps. Last year I had to put tape over all the screw holes in the underside of the dining table, because potter wasps were stuffing them with paralysed spiders (and the spiders kept falling out all over the floor).

As I write, the wasp has returned. Empty-handed this time, she’s fossicking around for a new place to raise her young. Maybe she’ll find one her caterpillars will stay in this time.

Sub-Alpine Idyll

We recently went on a lovely hike up Peak Hill, overlooking Lake Coleridge. The start of the track crosses paddocks, but once on the reserve land, the vegetation changes to a beautiful sub-alpine spread of daisies, Spaniard, matagouri, and tussocks. The daisies, in particular, were spectacular—so many were in bloom that the whole hillside looked frosted. The Spaniard was blooming, too, spiky flower heads rising above the daisies like something from a Dr. Seuss book. Native bees, mānuka beetles, and syrphid flies were all taking advantage of the abundance of nectar and pollen. The air hummed with insects.

You could be forgiven for thinking it was a beautiful, peaceful place. And it was, for us. But among the insects buzzing around were predators—pompillid wasps hunting for spider prey, robber flies snatching unwary insects out of the air, and birds snapping up bugs to feed to their young.

And then there were the plants themselves. At least one hapless beetle impaled itself on a Spaniard leaf. 

It may be pretty, but it’s a rough world out there when you’re insect-sized.

Alpine Delights

The family spent a delightful hour on the Dobson Nature Walk in Arthur’s Pass National Park on Wednesday. The track is an easy one, and hiking it quickly takes about 20 minutes. But it’s not a walk you want to do quickly, especially in summer. It winds through alpine and sub-alpine vegetation, including some beautiful tarns, and in summer, so many plants are blooming, it’s hard to take five steps without finding another lovely orchid, daisy, or hebe in bloom.

For me, the best part of the walk is the abundance of sundews in the tarns. As an entomologist, I’m naturally drawn to carnivorous plants like sundews. Sundews catch insects on the sticky hairs you can see glistening in this photo. The hairs are sensitive to both touch and taste, and when they sense a struggling insect, they fold inward to further entangle their prey. Enzymes exuded by the hairs then digest the insect, and the leaf takes up the nutrients in order to grow in the nutrient-poor alpine wetlands. 

These sundews were just beginning to flower—many plants had flower buds, but none had yet opened. The flowers sit above the leaves—an important adaptation, since the plant needs to be pollinated by the very insects it eats.

The alpine summer is short, so when these plants are done flowering, the leaves will slowly shrink into a structure called a hibernaculum that sits near the soil surface and protects the plant through the winter.

Catlin’s River Walk—a little bit of magic

My family and I were in the Catlins last week, in the southeast corner of the South Island. It’s a wild and remote area, home to more penguins and fur seals than humans. No urban adventures here—it’s a place for outdoor recreation.

One of the things we did was to hike part of the Catlins River Track (we didn’t have time to do the full track). It was unlike any other place I’ve been in New Zealand.

In fact, it reminded me most of eastern Pennsylvania, in spite of the fact that it shares not a single common species of plant or animal.

The track follows the Catlins River, a beautiful waterway that cuts through layers of limestone in one little cascade after another. Swing bridges cross the river several times, providing great aerial views of the water (and a little excitement for those who don’t like heights). The forest is old-growth beech which provides habitat for myriad native birds, carefully protected by intensive predator control. 

In addition to the beech, we were delighted to see two species of orchid on the forest floor, red-flowered mistletoes in the treetops, several species of slime mould, some lovely mushrooms, and a beautiful native harvestman. The birdlife was noisy and varied, but we weren’t lucky enough to see any endangered mohua. And, amazingly, there wasn’t a single sandfly! 

The whole effect was one of an enchanted forest. We were certainly enchanted.

The track is relatively flat—easy hiking for kids or those who can’t face the usual Kiwi hiking track going straight up a mountain, and because there’s no “goal” to reach, you can simply walk as far as you’d like, and then return. The entire length is 12 km one-way, with a return loop option through forestry land away from the river. 

I highly recommend this track. I’ll certainly be going back when I have enough time to do the whole thing.

A Weakness for Weevils

I was excited to find a new weevil on our property the other day. At least until I identified it.

Meet Otiorhynchus sulcatus—the black vine beetle—pest on a wide range of garden plants, including grapes, black currants and strawberries (all common in my garden).

I admit, I have a weakness for weevils—no matter how much of a pest they are, I think they’re cute. And this one is no exception. She’s lovely, in spite of her diet. And I’m certain she’s a ‘she’, because no males of this species have ever been found. The black vine beetle reproduces parthenogenetically, producing viable eggs without the need for fertilisation by males. 

This ability is the result of a bacterial symbiont in the genus Wolbachia. When researchers in California eliminated Wolbachia in black vine beetles (by giving the beetles antibiotics), the beetles’ unfertilised eggs were no longer viable. It’s a clever little ploy by the bacterium to ensure its own reproduction—only infected insects can reproduce, and they can do so without the trouble of finding a mate (I wrote more about this fascinating relationship in Putting the Science in Fiction and on Dan Koboldt’s Science in Fiction blog).

Another cool feature of the black vine beetle is that it is flightless. It’s not uncommon to find flightless insects and birds here in New Zealand, but it’s a little unusual to see it in invasive pests like the black vine beetle. Native to Europe, the black vine beetle is now distributed all around the world. Pretty impressive travelling for a 6 mm-long flightless insect.

Apparently black vine beetles can cause significant damage to plants. The larvae eat roots in the soil and do the most damage, particularly in potted plants, where root growth is limited. I’ve decided not to worry about them at the moment. I’ve got more damaging pests to worry about, and to be honest, I wouldn’t mind seeing them again. They are awfully cute.