Seasonal Changes of Population Density and Some Characteristics of Overwintering Nymph of Lycosa T-insignita BOES. et STR. : (Araneae : Lycosidae)

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Abstract

The seasonal changes in density of a Lycosa T-insignita population in an area of Tokyo showed two peaks, one appeared in spring and the other in autumn. The spring peak consisted mainly of the overwintered last instar nymphs and the adults which had emerged from these nymphs. The autumn peak also consisted of the nymphs larger than 1.0 mm in carapace width and the last instar nymphs which should overwinter. It was considered that this spider generally repeatd two genrations annually, since the adult emergence showed two peaks which appeared in spring and summer. According to the incubtion experiment started in a different period from Novermber of 1967 to March of 1968, it could be said that the overwintering last instar nymphs were inhibited in therir development into the adult stage during late autumn and winter, suggesting that they were in a state of diapause. The degree of this inhibition of their development appeared most strongly in the period from November to December. The development during this period seemed to be partly advanced when food was provided during the incubation period. The disappearance of the inhibition of development began to occur in January and thereafter accelerated as the season progressed. The intensity of resistance against hunger among overwintering individuals changed parallel to the change in the degree of inhibition of the development into adult.

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