70 Treubia Vol. Ill, 1. 



Oryctes. Mr. Leefmans (Med. 41 Inst. v. Plantenziekten, Buitenzorg 1920) 

 was the first to draw attention thereto. 



That so many more Lepidoptera have been collected is especially due 

 to using the light-trap. JACOBSON recorded only 10 species, though many 

 Heterocera were noted by him but are not listed. 



On this group of insects not much can be said before the material 

 has been worked out. Till now only some Danaids have been identified 

 by Mr. MOULTON (see List E); to some of these species we will revertin 

 Chapter IV. 



Noticeable is the occurrence on Krakatau of Schoenobius bipimctifer 

 Wlk., the well-known rice pest. It must breed here in wild-grasses, although 

 wild foodplants are unknown in Java or elsewhere. The only gall producer 

 among the Lepidoptera found on Verlaten I. is a species which causes 

 gall-formations on the leafs of Callophyllum inophyllum. 



To the Diptera not so many species could be added as to the other 

 groups of Insects. May be the great number of Diptera already collected 

 by Jacobson in 1908 is responsible for this. A complete list of the 

 Diptera found by him and identified by DE Meyere is given in Appendix B. 



For the gall-producing species, as for the other galls found on Krakatau 

 and Verlaten I., one should consult the papers of DOCTERS VAN LEEUWEN 

 (see Literature). 



Mosquitos, not abundant in 1908 according to jACOBSON's narrative, 

 are now a very great nuisance, especially at Verlaten I. North, the brackish- 

 water lake there being a suitable breeding place. This part of the island 

 is infested by these annoying insects in such a way that more than once 

 while lying at anchor in the northern bay of Verlaten I., we had to stand 

 out to sea in order to sleep peacefully. At least three species of mosquitos 

 have been caught, the larvae abounding in the lake on Verlaten I. and 

 also in the well and water-tuns on Krakatau. 



The increase of Rhynchota^ however, has been very important again ; 

 five times the number found in 1908 being collected on Krakatau. 



Worth being mentioned are the aquatic bugs; one species, a Notonectid, 

 as stated above, was found on Krakatau. On Verlaten I. I was able to 

 collect two species, a Naucorid and a Corixa. 



Noticeable among the Homoptera are the singing Cicadas. One rather 

 large species, Diindiibia rnjlvena WLK., is very abundant on both islands. 

 Every morning and evening we could hear their shrill sounds sustained 

 without interruption for just a quarter of an hour. They began exactly at 

 5.30 a.m. every morning and ended at 5.45 a.m ; every evening they lasted 

 from 6.30 p.m. till 6.45 pm. These times were noted in September; in 

 January the sounds arose a quarter of an hour later. 



This Cicada is not recorded by JACOBSON, but nowadays it is such 

 a noticeable insect on the islands that it would not have escaped his 

 attention if it was already present in 1908. 



