Abstract:
Jerking, which we defined as a pronounced and often repeated lunging of the
entire body, was studied in larvae among seven species of phytoseiid mites, and in the
nymphal stages of Neoseiulus fallacis (Garman). This behavior was observed in all
active immature stages of N. fallacis, and in larvae of six of seven species studied.
Jerking was usually triggered by direct contact with a conspecific predator or an active
immature stage of two-spotted spider mite, Tetranychus urticae Koch. With N. fallacis
larvae, jerking occurred occasionally without direct contact. Usually in these cases,
jerking occurred in response to the nearby movement of a mite, and less frequently, no
stimulus was observed. The larval jerking tendency, or the mean proportion of contacts
resulting in larval jerking, of a species was significantly correlated with a tendency to
congregate. Often in species with larvae having high jerking and congregating
tendencies, grouped larvae repeatedly probed their immediate area and each other with
their front legs. Species with larvae having higher mean jerking tendencies also had
higher mean numbers of jerks per jerking response. There was no consistent trend among
species in jerking tendencies of young, middle aged, and older larvae. Jerking appeared
to be a generalized response to any inter-individual contact, and not directed toward any
specific individual. Larvae of N. fallacis had a higher tendency to jerk than conspecific
protonymphs and deutonymphs, and had both the highest jerking and congregating
tendencies among larvae of all species studied. An individual was more likely to jerk
when approached by another mite than when it was the approaching member, and when
observed in approaching N. fallacis larvae, jerking often appeared aggressive. Jerking N.
fallacis larvae experienced fewer and shorter investigations, and fewer attacks from
cannibalistic adult females than anesthetized larvae that were unable to jerk.
