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Curiosities

1. Floor at the back door

Camera in normal mode

Early in April 2018 I was sweeping the kitchen, and when I swept in front of the back door and left the pile of dust in a sunlit spot I noticed some very small spots running back towards the door.


2. 'Aliens'

Camera in normal mode; Maximum focal length

I was intrigued, and when I looked by the door I noticed that there were a number of tiny spots (which I presume are some sort of mite) wandering around. The floor is vinyl, with a glossy surface, and near the door it reflects the light from the sky, and if I look there the mites appear as black spots. There are lots of tiny spots of dirt on the floor, so I can only pick out the bugs if they are moving. There is a dark band near the door and they disappear when they enter this, so I can't tell if they are coming in somewhere there. They also disappear if they get near the benches, and they just seem to be wandering around, not going anywhere in particular.


3. Enlargement of 2.

(Dots moved together)

I don't know what they eat; I tried putting spots of honey, cheese and assorted food crumbs on they floor, and an hour later 2 had drowned in the honey, but the rest were ignoring everything. I decided to try to photograph them, and got out my Pentax X90. It is an excellent camera for photographing scenery and flowers (if it's not windy), but has difficulty coping with moving objects, and poor light. It weighs only 430 grams, has a 26:1 zoom range (focal length 4.6 - 120mm: equivalent to 26-675mm on a 35m), and a macro mode which will focus down to 10mm.


4. Mite

Length ~2mm

However it does not do well in poor light, or with moving targets, as it is slow to focus. I call it my delayed action telescope; I can photograph the You Yangs (hills on the other side of the Bay, and then zoom in on a distant water bird which is completely invisible in the first photo, but I can't see any real detail until I upload the images and look at them on the computer. The camera is not well suited to photographing the bugs - there aren't that many of them, they don't like to be in the sun and you can't use the flash in macro mode, and they zip around erratically at relatively high speeds, so it is hard to follow them. It would be useless to try to use a tripod so I have to hand hold the camera and hope for the best. The 'tile' in 2. is 65mm wide.


5. Another mite

Length ~2mm

Photos 1-3 were taken in normal mode against the light, so although the vinyl is a redddish color it does not show. The remaining photos were taken in macro mode, and revealed that the pattern on the vinyl is very obviously screen printed. The mites are a greenish yellow color which does not show up well against it, making everything that much harder. I have taken more than five hundred photos, but only got a few reasonably good ones. As I was hand holding the camera every photo was a different magnification, and at a slightly different angle, and there is significant distortion in the lense.


6. Juveniles

Length ~ 0.5, 1, 2mm

However the pattern in the vinyl gave me a scale I could use to measure the insects, so I photographed a ruler on the floor to measure the pattern, and worked out how to print each photo at the same magnification. The scale on the photos is 4mm long. I soon noticed there were some even smaller juvenile insects, and eventually found that the size varied from less than 1mm to about 2mm. Once the insects get off the bright area they are almost impossible to see, but one morning I noticed one coming into the room, and managed to follow it several meters into the laundry. However this was very painful as I had to keep my bad neck at an awkward angle, and if I took my eyes off it for a moment, or it stopped for more than a few seconds, I would lose it.


5. Unknown mite

Length ~0.5mm

One evening, when I had about decided to give up my research, I dug up a clump of carrots for dinner, and before I went in I pulled off the leaves, and left them on a bench by the back door. When I picked them up in the morning to put them in the compost, there were dozens of mites running everywhere. I put some faintly ruled graph paper in the bottom of a flat bottomed cylindrical vase and shook the tops over it, getting some bugs among the dirt. I thought the graph paper would make it easier to get some good photos, but this hope wasn't fulfilled.


6. Argentine ants enjoying honey

Length ~ 3mm

I also tried gluing sheets of paper to the floor, and discovered that they did like crushed corn chips, but I still couldn't get good photos. I almost wonder if they realise that they are more obvious on the plain background; they certainly seem very aware of the approach of the camera, and zip off at high speed as I try to focus. One day I took three almost identical photos a few seconds apart and when I looked at them carefully I noticed an unrelated even smaller beastie which had moved slightly between each photo (5.).

The difficulty of photographing these mites contrasts starkly with the ease with which Argentine ants can be photographed. These love honey, don't mind sunlight, and are not at all shy, so it is much easier to get good photos (6).

 © Roger Riordan 2004-2019

Alien invasion

(Unknown mites)