When I came closer this large (ca. 7 cm, thumb 23mm) caterpillar of a Paradise Birdwing was troubled and protruded a pair of "red sacks" (Osmaterium) .
Ornithoptera paradisea (Paradise Birdwing)[det. by Keith Wolfe 2010, based on this photo]Tribe: Troidini (Birdwings)Subfamily: PapilioninaeFamily: Papilionidae (Swallowtail butterflies, Ritterfalter)Superfamily: PapilionoideaSuborder: GlossataOrder: Lepidoptera (butterflies, Schmetterlinge)Unfortunately I haven't seen the beautiful butterfly it becomes; but "Yawp Barbarian" shows an image:
www.flickr.com/photos/48605023@N00/3658008392/Indonesia, W-Papua, Manokwari, Arfak Mts.: Syoubrig, 1450m asl, 13.08.2010(IMG_3973)