The role of learning in the oviposition behavior of the silkworm moth (Bombyx mori)

Effect of host plant on the life history of the carnation tortrix moth Cacoecimorpha pronubana (Lepidoptera: Tortricidae)

The carnation tortrix moth, Cacoecimorpha pronubana (Hübner, [1799]) (Lepidoptera: Tortricidae), is one of the most economically important insect species affecting the horticultural industry in the UK. The larvae consume foliage, flowers or fruits, and/or rolls leaves together with silken threads, negatively affecting the growth and/or aesthetics of the crop. In order to understand the polyphagous behaviour of this species within an ornamental crop habitat, we hypothesized that different host plant species affect its life history traits differently. This study investigated the effects of the host plant species on larval and pupal durations and sizes, and fecundity (the number of eggs and the number and size of egg clutches). At 20°C, 60% RH and a 16L:8D photoperiod larvae developed 10, 14, 20 and 36 days faster when reared on Christmas berry, Photinia (Rosaceae), than on cherry laurel, Prunus laurocerasus (Rosaceae), New Zealand broadleaf, Griselinia littoralis (Griseliniaceae), Mexican orange, Choisya ternata (Rutaceae), and firethorn, Pyracantha angustifolia (Rosaceae), respectively. Female pupae were 23.8 mg heavier than male pupae, and pupal weight was significantly correlated with the duration of larval development. The lowest and the highest mean numbers of eggs were produced by females reared on Pyracantha (41) and Photinia (202), respectively. Clutch size differed significantly among moths reared on different host plants, although the total number of eggs did not differ. This study showed that different ornamental host plants affect the development of C. pronubana differently. Improved understanding of the influence of host plant on the moth's life history parameters measured here will help in determining the economic impact that this species may have within the ornamental plant production environment, and may be used in developing more accurate crop protection methodologies within integrated pest management of this insect.

Preimaginal conditioning affects oviposition choices in the silkworm moth (Bombyx mori)

Nowadays we can find a number of experiments that have showed the importance of learning in several situations related with survival of many animal species. For instance, knowledge acquired in the early stages of life could be crucial on the choice of egg-laying site. In this study we explored the influence of Pavlovian conditioning of silkworm larvae on their oviposition behaviour as adult female moths. For this, the larvae learning have to survive the metamorphosis and be shown in oviposition choice. In acquisition phase, a larvae group experienced an odour (conditioned stimulus) paired with mulberry leaves (unconditioned stimulus), another one experienced the odour and the mulberry leaves in an unpaired way and the last one experienced the odour alone during this phase. The results show that when these larvae became moths, only the first group preferred to lay their eggs near the odour when it was present during the test, so that associations learned during the larval stage seem to influence oviposition behaviour during adulthood.