Neumania papillator

Neumania papillator was first described by Ruth Marshall in 1922, the specific epithet papillator was applied due to its prominent papilla. John C. Conroy provides a technical description of the species in A Revision Of The Species Of The Genus Neumania Sensu Stricto In North America, With Descriptions Of Seven New Species (Third Part) (see References), and notes that whilst the species was originally recorded in Wisconsin, Louisiana, Tennessee and Pennsylvania he could not identify the precise location of the recorded Wisconsin population: he could not see the "Lauderlae Lakes" on any maps. The holotype collected by Marshall at this location on 13 August 1913 is currently held at the Field Museum of Natural History, as is the female allotype also collected by Marshall on 9 August 1915. Neumania papillator is soft bodied, covered with small spines and has six legs. John C. Conroy examined 13 males and 43 females, and recorded mean male lengths of 0.46 mm (range: 0.397-0.504 mm) and mean female lengths of 0.563 mm (range: 0.525-0.641 mm); Ruth Marshall's original description differed slightly with males and females recorded as 0.6 and 0.78 mm respectively. It has been recorded at a depth of 5 metres. Larvae of the Eastern forktail damselfly (Ischnura verticalis), larvae of skimmer dragonflies in the genus Libellula and adult water mites of the genus Limnesia have all been observed preying on N. papillator. == Behaviour ==

Both sexes of Neumania papillator are ambush predators - perching among the fronds of the aquatic vegetation, they hunt copepods (small crustaceans) which pass by in the water column. When hunting N. papillator adopts a characteristic stance termed the 'net stance' - their first four legs are held out into the water column, with their four hind legs resting on aquatic vegetation. This allows them to detect vibrational stimuli produced by swimming prey and thus orient towards and then clutch at the prey. - if a male finds a female, he slowly circles around her whilst trembling his first and second leg near the female. Sperm packet uptake by the female would sometimes follow. - but Proctor found a disharmony between sex ratios of Neumania papillator in the field and in laboratory conditions, with male biased sex ratios in the field and female biased sex ratios in the laboratory. Possible explanations for the male-biased field sex ratio were differential predation (predators eating females more than males proportionally) or it could have been caused by susceptibility to starvation, however these were refuted experimentally: invertebrate predators preferred males to females, and starved males died on average 40 days before starved females. The sex ratio at 'emergence' (the transition from deutonymphs (juveniles) to tritonymph (preadult resting stage) was female-biased, hence the discord could not be explained by any bias at emergence either. Proctor identified three remaining possible explanations for the differing sex ratios: • Differing depth preferences between the sexes combined with only sampling shallow regions; this could possibly be potentiated by female mites preparing for overwintering by burying themselves within the substrate. • Sweeping the net when collecting may bias the sampled sex ratio, if it is the case that when disturbed, females are more likely to cling strongly to aquatic plants whilst males are more likely to swim • If sex determination is environmental, then variation in light and/or temperature between the field and laboratory could produce the observed discord However Proctor noted that only hydryphantid mites (a subfamily of mites from the superfamily Stygothrombioidea (suborder Prostigmata)) have been observed burying themselves in the substrate to prepare for overwintering, that laboratory experiments found no evidence for sex-based disturbance responses and that environmental sex determination has not yet been observed in arachnids. == References ==