Insects and Invertebrates
Little Wittenham Wood and it's associated wetland habitats hold a diverse invertebrate fauna including many Nationally Rare (Red Data Book) and Nationally Scarce invertebrates.
The reserve's grassland areas have been less well studied, but have still proved interesting. Records go back to the 1940's, but the majority have been made since the 1980's. Over 1,000 species have been recorded.
Of the Insect groups dragonflies (Odonata), butterflies and moths (Lepidoptera), flies (Diptera, particularly hoverflies, soldier flies and craneflies), true bugs (Heteroptera), ground beetles (Coleoptera: Carabidae), various water-beetles and grasshoppers (Orthoptera) have been well surveyed. Other invertebrates, such as spiders (Araneae), snails and slugs (Mollusca), woodlice (Oniscidea), millipedes (Diplopoda) and centipedes (Chilopoda) have also received considerable attention.
Woodland inverts
Moth trapping in the 1980's recorded 276 species of 'macro-moth'. These include the tree dwelling species Strophedra nitidana (on Oak), Oncocera formosa (on Elm), Light Orange Underwing (on Aspen) and the White Letter Hairstreak Butterfly (on Elm). The White Marked moth (Cerastis leucographa) is associated with herbs of sheltered woodland edge.
Woodland flies have been well recorded. Three families, hoverflies (Syrphidae), soldier flies (Stratiomyidae) and to a lesser extent craneflies (Tipulidae), are particularly well recorded through casual surveys and various malaise trapping programmes. A Malaise trap looks and works rather like the fly-sheet of a ridge-tent and catches flying invertebrates, including many uncommon species not readily collected by hand netting. Of considerable interest is the large number of species associated with 'dead wood' micro-habitats. Bark fissures on over-mature Oak trees also provide a home for rare spiders such as Tuberta maerens (a Red Data Book species) and Zygiella stroemi. Other uncommon spiders associated with the foliage of shrubs and trees include Philodromus collinus, P. albidus, P. praedatus and Theridion familare.
The diverse spider fauna also includes uncommon species of damp shady leaf-litter, such as Pachygnatha listeri and Saloca diceros. Other leaf-litter dwelling species of note are the rare centipedes Lithobius muticus and L. macilentus, the millipede Brachychaeteuma melanops and the woodlouse Haplophthalmus montivagus. Despite considerable recording effort snails or slugs indicative of ancient woodland have not recorded from the Reserve. These include the most reliable indicators of long-term continuity of 'ancient woodland' and supports evidence that the woodland, although ancient, is secondary in origin.
Wetland inverts
Surveys by Pond Action in 1990 found the invertebrate interest of the two main woodland ponds to be of high and very high nature conservation value. The species found here reflect the well vegetated nature of the ponds. Examples are the caddis flies Leptocerus tineiformis and Holocentropus dubius; the aquatic bugs Cymatia bonsdorffi and Corixa panzeri; the water beetles Cercyon convexiusculus and Enochrus testaceus. The diving beetle Ilybius subaenus is of note for being considerably outside its usual north-western British range. These ponds are the main breeding sites for the reserves amphibians and dragonflies.
A large number of invertebrates are associated with lush marginal vegetation surrounding ponds or flushed areas. Good examples are the hoverflies Parhelophilus fruticorum and Anasymia contracta. The soldier flies are particularly diverse and includes several rare species associated with calcareous flushes, such as Oxycera analis and O. pardalina.
Grassland inverts
Bumblebees were surveyed across the reserve's grasslands in 1999. Seven species of true bumblebee (Bombus), including the south-eastern B. ruderarius, and four species of cuckoo bumblebee (Psithyrus), including Ps. rupestris were recorded.
Castle Hill is the only grassland area on the reserve that has been intensively surveyed for invertebrates. Here patches of flower-rich grassland hold a characteristic collection of species. These include the true bugs Berytinus montivagus and B. signoreti, the leaf-hopper Arboridia parvula and a good array of picture-wing flies (Tephritidae). Although no snails of note are found today, sub-fossil shells of Pupilla muscorum and Helicella itala (last seen alive in the 1940's) suggest that the turf must have been much shorter in the past. The rare soil-dwelling woodlouse Trichoniscoides helveticus lives in the crumbly chalk soils of the ramparts.
The shorter flower-rich areas on Church Meadow slopes hold a contrasting but equally important invertebrate fauna. Species of note include the 6-belted clearwing moth, the hoverfly Triglyphus primus, the spiders Argenna subnigra and Hahnia nava and snail Vertigo pygmaea. Both this area and Castle Hill support thriving and expanding colonies of Marbled White Butterfly.
The structural diversity offered by tall tussocky grassland provides good habitat for many invertebrates. Detailed surveys of the ungrazed grassland on Castle Hill have shown it to be particularly rich in invertebrates, including many uncommon spiders that require either a rough grassland structure or an undisturbed leaf-litter layer. Two Bush-crickets, Roesel's (Metrioptera roeselii), and the Long-winged Conehead (Conocephalus discolor) are both recent colonists to Oxfordshire.
