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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.
This is Diplora, our pet praying mantis.
Diplora, with (another) meal
Exoskeletons
We have kept praying mantis’ before. Diplora joined the team when she was still very small – to start with we fed her Drosophila (fruit flies) from our compost bin.
Diplora consuming a fruit fly (while upside down on the roof of a glass box)
Like other insects, praying mantis’s get their shape from a stiff exoskeleton, so to get larger they shed this outer layer from time to time.
Diplora in the process of moulting
Diplora has done this 3 times since we got her and we suspect she only has one more moult to go before she (or he) becomes fully adult.
Several exoskeletons from one mantid as it grew larger
One of the interesting things about this process (ecdysis) is that the exoskeleton retains a lot of the fine detail of the mantid, but with the advantage that we are able to examine it in detail – because unlike Diplora, the exoskeleton stays still while you have a good look at it.
Exoskeleton showing the compound eyes
We have enjoyed looking at details such as the compound eyes, the spikes on the forelegs, mouthparts (mandibles) and their fine antennae.
Exeskeleton showing antennae and the eyespots on the arms
Exoskeleton showing detail of forearms and an eyespot on the arm
Detail of abdomen
We have not yet fully captured the process on video, but here is some footage from someone who has (for a different species of mantid).
Compound eyes and pseudopupils
One thing that puzzled us with our mantids was the appearance of black dot in each eye – which isn’t always there, depending on the light. You can see it in the photos above, especially the one at the top. This is known as a “pseudopupil” and is essentially an artefact of the viewer. The compound eyes are made of many cones, with lenses over each. The lenses reflect some light, but in one position, relative to the viewer, no light is reflected, and so a dark spot appears.
This site has a series of photos of all kinds of insects showing this effect.
Chaos - it's not just a theory... 