|First instar larva, crawling up stem from lower leaf.|
The first picture is of a first instar larva, crawling up a stem of P. lobata. I believe it recently hatched from an egg down lower on the plant, and is now walking up to a leaf where it can feed. Based on its size, I estimate this larva to weigh about 0.5 milligrams. This is probably close to the weight of the egg that it hatched from. Given that I can't find the empty egg shells, I suspect it eats the egg shell as its first meal.
|Second instar larva, shown at the same scale as the one above.|
|Second instar larva actively walking across Passiflora vitifolia petiole.|
|Red-white Ptocadica, likely the same species as the larvae above.|
The life-cycle drawing summarizes the findings to date. Obviously there is a long way to go before being able to complete the drawing!
Comparing these larvae to the larvae of Heliconius, I find that the beetle larvae are slower-growing, with a relative growth rate of about 0.35 instead of 0.6. The egg stage is longer, 14 days instead of 10 days. The female beetle sits on the host plant for days in order to lay eggs, rather than the brief visit by the butterfly, and she eats the plant while waiting. My previously published work shows that Heliconius larvae are extremely vulnerable to predation by ants whereas my observations here at La Selva suggest that most Passiflora-attending ants pay no attention to flea beetle larvae. They seem effectively ant-proof, although experimentation is needed to determine this for sure.
I also began to test the shade house P. lobata larvae on a range of Passiflora species. If Red-white Ptocadica is the correct species for these larvae, I predict best performance (survival and growth) on P lobata, since this species seems to specialize on P. lobata as an adult food plant. More about his in the next blog posting!