Period of mating varies annually from 46 to 65 days during April to late June or early May to July. Lacebugs mated at any time of day but peak of pairing tended to occur about afternoon at field temperatures around I5°C. Duration of mating and angle between the sexes varies between pairs. In 55 % of pairs, males were to the right of females with dorsal surface of tip of male abdomen in contact with ventral aspect of that of female. Eggs are usually laid singly but occasionally in groups of 2-6 in thistle leaves. Oviposition in stems may occur at high adult densities in the laboratory. About 78-99 % of total eggs were laid in primary leaves, others in leaflets of axillary buds. Eggs were predominantly laid in midribs and other veins. Tingis eggs were implanted to varying degrees or seldom unembedded in leaf mesophyll with extrusion of part of chorion beyond non-oviposition surface in thin leaves. Oviposition rhythm was positively correlated with daily rhythm of physical conditions especially temperature. Six-hourly oviposition rate, proportion of females laying, and number of eggs laid per female increased from minimum between 00.00 and 06.00 hours to a peak at 12.00 to 18.00 hours and declined afterwards. Rate of oviposition and average fecundity varied annually according to temperature differential between pre-peak oviposition period of different years. Oviposition rate increased with temperature (in I965 and I966) and age (in I965) during pre-peak phase; but it decreased with aging of bugs in the post-peak phase when temperature had insignificant effects. Total fecundity in the laboratory or field varies considerably between individual females. At I5 and 20°C constant temperature, average numbers of eggs laid per female were 20 and 6I, respectively. Oviposition in laboratory tended to be periodic and females die without completing oviposition. Oviposition period varies annually in the field from I0 to I2 weeks, usually from early May to late July. In the laboratory this period varied with individuals and temperature from about 5.2 weeks at I5°C to at least 7.6 weeks at 20°C.