For the first time the pollination of a poorly known, terrestrial orchid, Habenaria pleiophylla Hoehne & Schlechter, 1921 (Orchidaceae) by a passion vine butterfly, Heliconius erato phyllis (Fabricius, 1775) (Lepidoptera, Nymphalidae) is reported. Number of pollinia-carrying individuals was determined on a population of H. erato phyllis in Horto Florestal Barba Negra, Barra do Ribeiro County, Rio Grande do Sul State. The pollination mechanism was described under laboratory conditions, in association with the butterfly feeding habit and the orchid flower morphology. Habenaria pleiophylla pollinia are cemented during nectar feeding on the ventral portion of the compound eyes near H. erato phyllis proboscis base. The pollinia are transferred to the stigma of other flowers during subsequent visits. Both males and females of H. eralo phyllis frequently visit H. pleiophylla flowers in the Barba Negra Forest. About forty percent of field collected adults had attached pollinia, ranging in number from one to 19 per individual. Thus, H. eralo phyllis may play an important role in the reproductive biology of this H. pleiophylla population.

Oviposition response of Heliconius erato phyllis (Fabricius, 1775) (Lepidoptera, Nymphalidae) to variation in host plant availability, Passiflora suberosa Linnaeus (Passifloraceae), and to presence of conspecific eggs and larvae was determined through choice experiments performed under insectary conditions. Freeze dried, painted eggs and larvae were used as mimics for testing presence of conspecific effects. Females laid more eggs on intact P. suberosa shoots without conspecifics than on those with H. erato phyllis egg and first instar mimics in both simultaneous and sequential choice trials. Oviposition response to variation in host plant availability was determined through no-choice trials, under host plant densities varying from 0.3 to 8.3 plants per female. Number of eggs laid per plant decreased exponentially with an increase in plant availability. On the contrary, daily oviposition rates (eggs /female/day) increased with an increase in plant number, and levelled off when the number of plants available for oviposition was greater than potential fecundity of females. Thus, it is inferred from the results that females assess egg and larval load and prefer to lay eggs on shoots free from conspecifics. It is also inferred that they are able to recognize plant abundance and are unwilling to lay more than one egg per shoot even when host availability is scarce, as judged by reduction in daily oviposition rates under low host plant number. The consequences of laying isolated eggs on P. suberosa shoots are discussed from the viewpoint of intraspecific competition in the larval stage of H. erato phyllis.

Oviposition site selection of Heliconius erato phyllis (Fabricius, 1775) (Lepidoptera, Nymphalidae) was studied when size of and damage on shoots were variable in a natural population of Passiflora suberosa Linnaeus (Passifloraceae), and through sequential and simultaneous choice experiments performed under insectary conditions. Females showed marked oviposition preference for undamaged and largest shoots of P. suberosa. Eggs were mostly laid on the terminal buds of intact shoots under natural conditions. In simultaneous choice trials, females preferred to oviposit on shoots from which leaves (ten) were removed but the terminal bud maintained to those where leaves were kept but the terminal bud was cut out. In sequential choice trials, they did not lay eggs on shoots from which the terminal bud was removed. Females preferred to oviposit on large to short intact shoots in both sequential and simultaneous choice trials. Females laid eggs preferentially on shoots with the greatest leaf area when most plants were intact in the field during early spring. Later in fall, when mostly large, old shoots were damaged or in a reproductive stage (less desirable for oviposition), oviposition intensity was highest on the shortest, youngest shoots of P. suberosa. Thus, females might rank these quality attributes higher than size while selecting shoots for oviposition. The consequences of ovipositing selectively on intact, large shoots of P. suberosa are discussed from the view point of H. erato phyllis larval performance.