Leaf-rollers, as the term suggests, are organisms that roll leaves to form shelters - unlike galls, the plant doesn't grow new structures, although there is some overlap (excuse the pun) with some leaf-rolls including further distortions such as thickening and increases in cell number, and hence being considered galls (Redfern & Shirley, 2011). In this case, the roll in a willow (Salix) leaf (found at Winnall Moors on the edge of Winchester, southern England) involves twisting and thickening of the plant tissues and so is classed as a gall (only just - sometimes the thickening is very slight).
|Willow leaf roll showing twisting and thickening (increased cell size is visible in places)|
|The roll unrolled - at first glance there is nothing but frass (invertebrate faeces)|
|Looking more closely, a few pale creamy-white rounded-oval eggs can be seen, each no more than 0.5mm in diameter. Whatever they are, an adult invertebrate was here recently. We'll return to these later...|
|A small cocoon of tangled silk. The lid (top right) is detached showing that whatever developed here has now left.|
|The bottom of the cocoon showing attachment threads plus a dark patch that may be frass.|
|An unidentified exuvium - probably one of the Hemiptera (true bugs) with clearly defined wing buds and abdominal segments.|
|That's more like it - something recognisable, an exuvium of a small spider; even the leg hairs are clearly visible.|
|Dorsal view of the tiny spider (a few mm long) found in the leaf roll.|
|A close-up showing various appendages and some of the eyes.|
|Ventral view of the insect showing the pointed 'snout', long antennae and spotted wings held in a tent-like position.|
|Dorsal view of the head showing protuberant compound eyes and orange simple eyes (ocelli). Note the patterning on the head and the bristly antennae.|
And so, that brings us to the end of the specimens that could be identified (to some extent at least) at the time of collection about two weeks ago. However, I did mention that we would return to the eggs. Once found, I put them on their section of leaf in a small container to see if they would hatch, and they did...
|Tiny larva about 1mm long - dorsal view|
|Ventral view showing segmented legs.|
|Ventral close-up of the head and thorax.|
So, at present, I have identified all the organisms within this single leaf roll as far as I can. I hope it shows the importance of such small-scale habitats and the diversity they support, as well as highlighting some groups that are likely to be under-recorded due to their small size and tendency to hide. These under-recorded groups and habitats are worth taking the time to investigate as there are discoveries to be made that might be in your local patch of habitat or even your garden or back yard. Happy bug-hunting!
Cooter, J. & Barclay, M.V.L. (eds.) (2006). A Coleopterist's Handbook (4th ed.). AES, Orpington.
New, T.R. (2005). Psocids. Psocoptera (Booklice and Barklice) (2nd ed.). RES Handbooks for the Identification of British Insects 1(7): 1-145.
Redfern, M. & Shirley, P. (2011). British Plant Galls (2nd ed.). FSC, Shrewsbury.
van Emden, F.I. (1942). Larvae of British Beetles. III. Keys to the families. Entomologists' Monthly Magazine 78: 206-272.