The pseudoscorpion Chthonius kewi in North Nottinghamshire and a note on its breeding.
The Naturalist (1972) 97 142. C.A. Howes
The pseudoscorpion Chthonius kewi new to science in August 1961, was discovered at Colne Point, near St. Osyth, Essex Specimens collected then and subsequently in July and August 1963 and July 1964, were extracted by the use of a Tullgren funnel from Agropyron litter and other debris at the base of the sea wall (Gabbutt, D. P.)
A new species of pseudoscorpion from Britain. J. Linn. Soc. Lond. 150, 165-181, 1966).
No further discoveries of C. kewi were made until Messrs. Peter Skidmore and Colin Johnson collected two specimens and a probable third at Idle Stop, North Nottinghamshire (Grid. Ref. SE 725982), only a few yards from the Lincolnshire border and about 2 miles from the West Riding border. The specimens were sieved from heaps of rotting aquatic plants (Potamogeton, etc.) dredged onto the banks of the Warping Drain.
The three specimens were examined in 50% alcohol by C.A.H. and worked out to members of genus Chthonius C. L. Koch. As one of the specimens recovered from the immersion and examination it was kept alive in order to make observations on its feeding and behaviour. The two preserved specimens were sent for determination via Mr. P. Jones to Dr. P. Gabbutt who confirmed them as 1 male and 1 female C. kewi.
The specimens are now in the Arachnida collection at Doncaster Museum and Art Gallery.
The live specimen was kept in the dark in a corked test tube at a temperature of about 65°F. On 27th June the beginnings of a silken chamber were noticed, spun across the angle of the tube’s base. By 30th June the chamber was complete and constructed like an elliptical canopy. The pseudoscorpion was sealed between the silken canopy and the glass of the test tube, but still freely moved about inside the chamber. On 12th July a cluster of eggs was noticed; there appeared to be five eggs in a pentagonal arrangement. The cluster appeared to be secured to the silken canopy and not to the parent, she still being able to move with agility around the chamber. When the tube was moved, or the area of the silken chamber tapped with a pencil, the female would extend its pedipalps and open its pincers in an aggressive stance orientating itself towards the area of disturbance. By 20th July the eggs had hatched, and the larvae could be made out still within the sac which had encased the eggs.
On 29th July the protonymphs were free from the egg pouch. At least five could be seen, though with dirt and distortion of the glass in the base of the test tube the exact number could not be made out and, as they moult after leaving the “pouch”, the spent skins may have further confused the situation. The protonymphs moved freely around the chamber and on occasions the parent could be seen apparently feeding them individually through their mouth parts coming into contact. As observations had to be discontinued for a week a small fruit fly was placed inside the test tube for the brood to feed on following their emergence from the silken chamber. Unfortunately, the parent and brood did not survive and on the 9th of August they were all found in a very desiccated state still within the silken chamber.
The specimens were dispatched to Dr. Gabbutt but were in too poor a state to be positively determined as C. kewi.
According to Dr. Gabbutt (pers. comm.) the observation concerning the female being independent of the egg mass is new, since in all reports of other members of the Chthoniidae (see especially P. Weygoldt: The Biology of Pseudoscorpions Oxford University Press, 1969) the eggs are retained in a “pouch” by the female and supplied with a nutritive fluid until a few days after the protonymphs have hatched.
C. A. Howes