72 Treubia Vol. Ill, 1. 



Remarkably enough, of Myriapoda I have found even less species than 

 Jacobson 13 years ago. This is the more surprising as I paid so much 

 attention to the surface fauna. The phosphorescent species noticed on the 

 summit of Krakatau by the topographic surveyors in 1908 was probably a 

 species of Geopliiliis occurring everywhere in houses. Perhaps this species 

 was introduced with the luggage of the explorers. But even if we deduct 

 this species from jACOBSON's number, there is still a decline in 1920 — 1921. 



Further, JACOBSON stated that the large Scolopendras were even 

 annoying at the time of his visit. Nowadays this species, although not rare, 

 is far from abundant, as also the large Spirostreptns-speciQS, Whether the 

 decrease of Myriapods is due to the wood getting thicker or to the appear- 

 ance of their enemies on the islands, must be left undecided» 



The number of Arachnida, however, went up considerably. Of this 

 Class of animals four times the total of 1908 has been brought together 

 on Krakatau. 



The number of Spiders on this island has tripled; also many mites have 

 been collected, none of which are recorded by JACOBSON, except an Ixodid 

 living on Varanus, This species, just as other external or internal parasites, 

 I have excluded from List. A, in so far as these species cannot have reached 

 the islands independent from their hosts. The majority of the mites consists, 

 however, of gall-producing species, only five free-living species having been 

 found. The Scorpionid mentioned by JACOBSON could not be found again. 



Of Crustacea only the truly terrestrial forms are of importance; all 

 those crabs and Pagurids haunting the beach, the larvae of which live in 

 the sea, Vv^e can here leave out of consideration. The same number of 

 Oniscoids (3 species) as in 1908 are met with on Krakatau; on Verlaten I. 

 only one species was found, but very abundantly, hi addition a terrestrial 

 Amphipod (Orchestia) occurs on this island, a species also common on Java. 



The land Mollusca on Krakatau have increased from 2 in 1908 to 5 

 in 1920 — 1921, and on Verlaten I. from to 3. Three of the species from 

 Krakatau are very small ones and belong to the surface fauna, living in 

 mould and decaying leaves. The two others are the Bulimulus already 

 recorded by JACOBSON, and a Scarabus. Bulimulus has been noticed on 

 Krakatau by DOCTERS VAN LEEUWEN also at an altitude of 500 and 800 M. 

 Scarabus is now so common on both islands that JACOBSON would 

 not have overlooked the species if it had been present in 1908. This mollusc 

 is living under dead leaves in small ravines near the coast and can stand 

 excessive drought. I collected a few of these Scarabus in September 1920, 

 keeping them in a tin box without any moistening for 35 days! All this 

 time they remained motionless but they revived at once after making them 

 wet. However, I could not find again the P///?///ß mentioned by JACOBSON. 



True earthworms were not yet found in 1908; the Pheretima noticed 

 by Jacobson was a species living always in decaying wood. Now earthworms 

 are fairly common on Krakatau, but they are still absent on Verlaten \. 



