Further monthly records (1994 to 2000) of size and abundance in a population of the "Australian" flatworm, Australoplana sanguinea alba in the UK

Collections of the "Australian" flatworm, Australoplana sanguinea alba, hav e been made in one garden in the UK three times a week from February 1995 t o September 2000. All specimens seen were placed in 70% alcohol, one jar ea ch month. Flatworms were counted but not collected for some months from Mar ch 1992. The first flatworm was seen in December 1991. Rainfall, soil moist ure and air and soil temperature (and latterly, the depth of the water tabl e) were recorded. All specimens (5121) were weighed and measured. For some years the maturity of each specimen was also determined. Fewest flatworms a re found in July and most in November. Seasonal variation is probably relat ed to soil moisture content. Relatively low rainfall in the winter of 1995- 6 apparently led to low numbers of flatworms the following winter. Average size of flatworms is smallest in July and largest in March. Apparent hatchl ings are most abundant August to October. 80% of the specimens were mature. Immature flatworms form the majority only between July and October. Specim ens as small as 9.5 mm long are mature. Only four egg capsules have been se en over eight years. Flatworms have been observed undergoing fission and it is suspected that fission may be the main method of reproduction in this p opulation. Body weight varies with the square of body length (exponent = 2. 093).