Sunday, 13 January 2013

A cool harvestman

Today I came across an unmistakable harvestman species, Dicranopalpus ramosus. This species has - or is in the process of - colonising Europe from its original home in North Africa. It is unclear if this expansion has or not anything to do with human transportation, but it has been suggested that it could could have been introduced with garden plants or horticultural produce, and the species has carried on expanding. It was first noted in the UK in 1957, and reported in Scotland in 2000.
 This is the second time I spot this harvestman. The first time (07/11/2009), was in the same location and also on a headstone (above). They have a typical resting posture, close to the substrate, with their long legs outstretched to the sides, and they often rest alongside leaves or branches this way. When resting on walls - or in this case on headstones - they are easy to spot. The second distinctive feature is that, their palps are forked. Males have a dark mask across the eyes and plain bodies about 4 mm in length, females have pale eye region and dark patterns in their body, palps and legs. 
Adults are found from the end of July onwards, peaking in September, apparently happy to live until February or March if the frosts don't kill them. 

A female
Male showing the usual stretched posture.
Close up of the same male.

No records were available for East Yorkshire, so these now have been uploaded into iRecord.

More information
Page in the British Spiders site.

Saturday, 12 January 2013

House spider with egg sac

Under the lid of the water butt in the garden I found this small Tegenaria, guarding its curious egg sac. I had never seen a Tegenaria egg sac before, the reason being that, according to W.S. Bristowe, their egg sacs are normally attached inside the spider's funnel, where they would be hard to see. In this case I probably broke the funnel when opening the lid and the egg sac seems to hang from the plastic by a few threads of silk. This peculiarity and its small size compared to other Tegenaria specimens make me think it is T. domestica, a species found in or outside houses. I hope I didn't disturb the spider too much, as I plan to follow the development of her spiderlings, which stay with their mums for a few molts inside her funnel.

Thursday, 10 January 2013

Longtailed mealybugs

A few years ago I bought a house plant, Clivia miniata, and soon after I realised it was infested with Longtailed mealybugs, Pseudococcus longispinus. These are pests of many agricultural plants in warm regions and greenhouse or house plants in colder areas. I was reluctant to get rid of the plant, since has flowered nicely every winter, so I keep the infestation in check by regularly wiping the leaves. Today I checked the plant and realised it had quite a few visible mealybugs so I gave them a quick photographic session, experimenting with a little 400x Veho microscope.
At first sight, infested plants appear to have small powdery patches on their leaves, especially on the underside. On close inspection, weird whitish bugs become apparent, and these are actually insects, with sucking mouthparts. This species has 17 pairs of lateral projections, four of them are long filaments on their rear ends. Under the microscope, their six legs are visible under their bodies, although they are hidden under their lateral projections when looked from above. Mealybugs are covered on a waxy white substance that looks like desiccated coconut, and hair-like fibers. They are soft insects and this is  their protection against predators, although lacewings, ladybirds can predate them, and they are also parasitised by wasps.
The lateral projections and fibers of an adult mealybug
Individuals of different sizes cluster together. The larger ones are adult females. They are wingless and have little mobility and they can reproduce parthenogenetically. The smaller individuals are nymphs, and have shorter lateral projections.
They are quite mobile, as you can see in this video.



The first stage nymphs - just visible with the naked eye - are called crawlers. They are yellowish, and have little wax. I found it impossible to take a photo of them under the microscope, as they walk surprisingly quickly. They appear to be a dispersal stage in the wild, as they are easily blown away by the wind and thus transported to nearby plants. Males do exist, although they are quite rare, and they look completely different. They are winged and lack the waxy coating of females.

More information
Mealybug info.