The effects of oviposition-deterring larval tracks of four aphidophagous coccinellids and two chrysopids were investigated on females of four coccinellid species in choice tests. Aphidophagous coccinellids Cycloneda limbifer Casey, Semiadalia undecimnotata (Schneider) and Coccinella septempunctata L. laid significantly fewer eggs on sites with tracks of unfed conspecific first instar larvae than on clean sites, but Leis dimidiata (F.) laid similar numbers of eggs on both sites.
In some but not all species, tracks of heterospecific predators also deterred coccinellid females. Interspecific effects were stronger between some allopatric species than between the sympatric coccinellids C. septempunctata and S. undecimnotata. C. limbifer laid relatively few eggs on sites previously exposed to larvae of S. undecimnotata and L. dimidiata. S. undecimnotata avoided sites with tracks of L. dimidiata larvae. The two smaller species, C. limbifer and S. undecimnotata, laid considerably fewer eggs per batch than the larger coccinellids, C. septempunctata and L. dimidiata. C. limbifer and S. undecimnotata oviposited similar numbers of eggs on clean sites and sites with tracks of chrysopid larvae of the species Chrysopa oculata and Chrysopa perla. Females of C. septempunctata laid fewer eggs on sites previously exposed to larvae of C. oculata but not C. perla.
Densities of faecal spots of coccinellid females on clean substrates and substrates with tracks of predatory larvae differed significantly in only one choice test (C. limbifer females exposed to tracks of S. undecimnotata larvae). This indicates that the presence of larval tracks affects where females lay eggs more than where they search.
The persistence of oviposition-deterring effects of coccinellid and chrysopid larval tracks on females of three aphidophagous coccinellid species was compared. One month old tracks of first instars of the coccinellid Cycloneda limbifer Casey deterred conspecific females from oviposition in choice tests with clean and contaminated substrates. Intraspecific effect of larval tracks in Semiadalia undecimnotata Schneider was statistically significant after 10 days. Although fresh tracks of conspecific first instars effectively deterred females in both tested populations of Coccinella septempunctata L., deterrent effects disappeared when tracks of larvae were only one day old. However, females of C. septempunctata laid fewer eggs on sites with 10 days old tracks of Chrysopa oculata Say or sites with one month old tracks of Chrysopa perla (L.) first instars than on clean sites. In contrast to females of C. septempunctata and S. undecimnotata, C. limbifer females left significantly more faecal spots on clean sites than on sites with 5-30 days old tracks of conspecific first instars. This indicates that sites with tracks of larvae can also effectively repel conspecific females of some coccinellid species from searching.
Choice tests showed that tracks left by coccinellid larvae have generally little effect on oviposition site selection by chrysopid females. Fresh tracks of first instar larvae of the coccinellid species Coccinella septempunctata, Cycloneda limbifer, Leis dimidiata and Semiadalia undecimnotata, did not deter females of the chrysopid Chrysopa oculata from laying eggs. Females of Chrysopa perla avoided ovipositing only on substrates with tracks of L. dimidiata larvae.