J66 



Himaii — Our Living Resmirces 



2,000 



Fig. 3. The island distribution of 

 native inscet species. 



100 



80 - 



60 



40 



20 





1,000 



500 



o ^ 



— ' w> -r 



oQ 



- Maui Nui -^ 

 island complex 



Fig. 4. Species and total catch 

 composition of wasps in the 

 families Braconidae and 

 Ichneumonidae in a high-elevation 

 mesic forest on the Hawaiian 

 island of Kauai. Wasps were sam- 

 pled from January 1992 to January 

 1993 by using a Malaise trap. 



fauna is readily apparent from the eontrast 

 between historical collections and reports (e.g.. 

 Perkins 1913; Zimmerman 194!S) and more 

 recent records and surveys. This change is par- 

 ticularly obvious in lowland areas where land 

 conversion (Cuddihy and Stone 1990) and the 

 establishment of alien species have eliminated 

 or drastically reduced the abundance and diver- 

 sity of native arthropods. For example. A.squith 

 and Messing (1993) found that less than 10% of 

 the insect fauna of a lowland agricultural area 

 on Kauai is composed of native species, and. at 

 a low-elevation site on the island of Hawaii, 

 even the arthropod community on the native 

 tree "Ohi "a lehua {Metrosidews polyniorplui) 

 is composed primarilv of alien species (Gagne 

 1979). 



■ Biocontroi At higher elevations in more intact vegeta- 

 □ Non-native tive communities, invasive alien arthropods 



■ Native hd\'c become dominant in some guilds, such as 



honey bees as pollinators and millipedes and 

 isopods as detritivores. The effects of predatory 

 species, such as the Argentine ant {Linepithema 

 hiimiUs: Cole et al. 1992) and the western yel- 

 lowjacket (Vespula pensylvanica; Gambino et 

 al. 1990). in the decline of some native groups 

 are well documented. 



Introduced Parasites 



Although the native Hawaiian faunas natu- 

 rally bear some pressure from parasitoids. with 

 endemic taxa of wasps in the families 

 Ichneumonidae. Bethylidae. Diapriidae, 

 Eucoiliidae, and Eulophidae, and the fly family 

 Pipunculidae. the taxonomic composition and 

 therefore the ecology of parasitism itself have 

 been altered by the addition of alien species. For 



example, the Hawaiian Islands originally had no 

 native species of braconid wasps, but now har- 

 bor 76 species in 42 genera (Nishida 1992). 

 Many of these parasitoids aie not confined to 

 disturbed habitats or alien hosts. By using a 

 Malaise trap (a tentlike net left in place to cap- 

 ture flying insects), A. Asquith and M. Kido 

 (USFWS and University of Hawaii, Kauai, 

 unpublished data) recently sampled the para- 

 sitic wasp community in a high-elevation native 

 mesic forest on the island of Kauai for a full 

 year. Of the 17 species of Braconidae and 

 Ichneumonidae captured, all but one are para- 

 sitoids of moth larvae and pupae, and all but 

 two are known to attack native Hawaiian moths. 

 No known species of native ichneumonid wasp 

 in this forest is extinct, and the endemic taxa 

 still contribute the most to species diversity 

 (Fig, 4). Human activities, however, have essen- 

 tially doubled the number of species parasitiz- 

 ing native Lepidoptera. Furthermore, parasitoid 

 abundance in this community is dominated by 

 non-native species (Fig. 4), with less than 1 in 

 10 parasitoids being native to Hawaii. On a 

 numbers of individuals per species basis, the 

 two species introduced for biological control 

 {Erihoni.s sinicits and Meteorus laphygmae) are 

 more invasive in this forest than the supposed 

 inadvertently intixiduced species of parasitoids. 

 Not only have these introductions increased the 

 number of species and individuals parasitizing 

 Hawaii's native Lepidoptera. but also the new 

 species have searching and immobilizing 

 behaviors to which the native fauna is unaccus- 

 tomed. 



Populations of the native stink bug 

 (Pentatomidae) genera Coleotichus and 

 OecluiUa dramatically decreased after 1962 fol- 

 lowing the purposeful introductions of a 

 tachinid fly and several scelionid wasps for bio- 

 logical control of the non-native pest, the south- 

 em green stink bug (Nezara viridiila). The koa 

 bug (Coleotichus blackbunuae) is the largest 

 and most spectacular native Hawaiian true bug 

 and was, until the early 1970's, common on all 

 the major Hawaiian islands, including within 

 the city of Honolulu, where it could frequently 

 be found on introduced acacia trees. Numerous 

 specimens were deposited in the insect collec- 

 tions of the Bishop Museum and University of 

 Hawaii every decade from 1890 to 1970, but 

 very few specimens have been seen since 1978. 

 Because the koa bug is conspicuous, and its rar- 

 ity has been publicized (Howarth 1991 ), its pop- 

 ulation decline seems real and not an artifact of 

 survey effort. 



Since the koa bug is gregarious and hun- 

 dreds of individuals could be collected from a 

 single tree, it was used as an alternate host for 

 rearing introduced parasites before their release. 

 Thus, circumstantial evidence implicates these 



