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On a recent visit to Travis Wetland we saw many webs of the nursery web spider (Dolomedes minor), which builds a nest to protect its young.
The spiders typically build these nursery in low growing shrubs, such as this Coprosma bush. The nest below is probably about to be vacated by the spiderlings.
We did get a (somewhat blurry!) video of the seething mass of spiderlings.
We didn’t see any of the adult spiders, though apparently the females were probably hiding nearby – they guard the nests at night. The nest below is now empty, though there is a spider on the bottom left, perhaps a juvenile?
There is detailed information about the Dolomedes genus in New Zealand here. There are four species here, with Dolomedes minor being the most common.
For more photos, including of the adult spiders, see here.
We had a short visit recently to one of the waterways that runs through Styx Mill Reserve, in Christchurch. The ~60 ha site has an interesting mix of vegetation types (mainly wetland and riparian areas), and even some locally rare plants. But on this occasion we went to look for arthropods – both in and around the water.
Below are a few of our finds. Our thanks to the folks at NatureWatch for help with the identifications.
The forest shield bug (Oncacontias vittatus):
Another immature shield bug, probably a Rhopalimorpha sp.
The New Zealand pond-skater (Microvelia macgregori):
The larvae of a mosquito/midge (Family Dixidae)
A longjawed orb weaver spider (genus Tetragnatha):
And this is the same spider making itself as thin as possible, presumably for hiding:
There is a guide to many of the species in the reserve on the Landcare website here and the reserve is part of the Styx Project. There is also a comprehensive booklet about Christchurch Waterways available from Environment Canterbury here.
We have been working on ways to take photographs of insects at home. Here are some of the tools and techniques we have found useful:
We have been using an iPhone 5 with the OlloClip 4-in-1 macro lens. This gives us a magnification of 15 x – which is better than many hand lenses.
Magnification inevitably results in a shallow depth of field, so achieving a clear focus requires care. The iPhone camera software allows you to lock the focus, if you tap and hold until the square yellow box flashes around your finger. The Olloclip software doesn’t appear to allow this, although it does allow you to set the focus and exposure on separate parts of the image, which is sometimes useful too.
To keep it steady, the camera is held on a tripod with a glif attachment to hold the phone on.
C has made a scissor-lift (out of FischerTechnik) to enable us to do fine height adjustments of the subject, relative to the camera. The lift has a threaded rod, and turning a handle moves the platform up and down relative to the camera. This degree of fine control was not possible with our tripod, but the lift ensures it is easy to make frequent small adjustments.
We have a piece of plain paper on top of the platform to give a neutral background.
J has built a small glass container, approx. 80 x 50 mm, which stops any live subjects from roaming too far. They can still wander/skitter out of view, but it increases the chances of capturing a photograph. The box is made of 3 mm picture glass, glued together with a silicone glue (RTV). You can often get glass off cuts from a picture framer.
The sides of the box are only 11 mm high (with a glass lid on top of that) which enables us to get sufficiently close with the camera. For some creatures you can take the lid off – but for the more mobile individuals, that is not an option.
The flat sides also mean we can get clear photos from the side – unlike the distortions you get with a petri dish or a plastic container.
Any moving of the insects that is required is done with a fine paint brush.
Lighting is also important. Natural light (although not direct sunlight) is sometimes sufficient, since we are using a tripod. When it isn’t, we use an LED torch.
The reason for using LED’s is that (unlike a tungsten bulb) it doesn’t produce much heat, so it doesn’t overheat the creature below.
Here are some examples of our results so far, of insects found in several Christchurch gardens:
This same general setup is also useful for photographing other subjects, such as the details of plants, rocks, shells etc.
Some ideas we have yet to try include:
- Try some focus-stacking software – this involves taking a series of images, each focusing on a different plane, and then the software stitches them together into a single clear photo.
- Find some way of aligning the camera to the eyepiece of our stereo microscope, that provides 40x magnification.
- Perfect a cooling box which will slowly cool an insect just enough to slow it down for photography, but that will also allow it to subsequently warm up and recover.
- Build a tall narrow (approx. 11mm wide) aquatic observation tank, for photographing more of the small creatures from ponds and aquariums – something like this. And find a suitable lighting method for aquatic subjects.
Do you have any tools/techniques you can recommend?