Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
10 years; the last specimen was seen in 1993 at Hualālai (Foote 1999). Thus, the population of D.
heteroneura at the KFU is the only known extant population of this species (Haines and Foote 2005).
Drosophila heteroneura is endemic to the island of Hawai„i and restricted to montane wet „ōhi„a and
mesic koa „ōhi„a forests on the west side of the island. Historically, D. heteroneura was relatively
widely distributed between 3,400-6,000 ft above sea level. The picture-wing fly has historically been
observed at Hualālai, Mauna Kea, Mauna Loa, and Kīlauea in five different montane environments
(Federal Register 2006a).
The life-history of D. heteroneura requires breeding on the bark and stems of Clermontia (especially
C. clermontioides) and Delissea spp. The larvae primarily inhabit the decomposing bark and stems of
these two plants, but it is also known to feed within decomposing portions of Cheirodendron sp. in
open mesic and wet forest habitat (Foote 1999, Federal Register 2008b).
According to the Designation of Critical Habitat for 12 species of picture-wing flies from the
Hawaiian Islands (Federal Register 2008b), D. heteroneura has two Primary Constituent Elements or
habitat features that are essential to the conservation of the species. These features include: (1) mesic
to wet, montane, „ōhi„a and koa forest; and (2) the larval host plants Cheirodendron trigynum subsp.
trigynum, C. clermontioides, C. hawaiiensis, C. kohalae, C. lindseyana, C. montis- loa, C. paviflora,
C. peleana, C. pyrularia, and Delissea parviflora.
Five critical habitat units are designated for D. heteroneura within the Designation of Critical Habitat
(Federal Register 2008b). Three of the units: Ka„ū Forest Reserve, Pit Crater, and Waihaka Gulch –
occur on State or private land, and total 291 ac. An additional 687 ac in Lower Kahuku owned and
managed by Hawai„i Volcanoes National Park comprise another critical habitat unit. Finally,
3,604 ac within the KFU are occupied habitat and have the necessary features that are essential for
the conservation of D. heteroneura; thus they are designated as the fifth critical habitat unit (Federal
Register 2008b).
Threats to the picture-wing flies include habitat degradation by ungulates, loss of host plants, and
impacts of nonnative insect predators and parasites such as ants and wasps. The species is also eaten
by native species such as the caterpillar Eupithecia staurophragma (Howarth and Mull 1992). The
construction of an ungulate exclosure and rat control will remove the primary threats to D.
heteroneura within the KFU (USFWS 2008).
4.8.2 Koa Bug (Coleotichus blackburniae)
The koa bug (Heteroptera: Scutellaridae) is a rare iridescent, blue, green, maroon, and yellow stink
bug. Measuring almost an inch in length, Coleotichus blackburniae is the largest native true bug
(Howarth et al. 2003). Historically, this species was common on koa and a„ali„i (Dodonaea viscosa)
on the islands of Hawai„i, Maui, O„ahu, Kaua„i, and Moloka„i. Currently, the koa bug is rarely found
in the State. The koa bug does occur at the HFU (Jeffrey, pers. comm.).
Information on the koa bug is scarce. Adults and nymphs feed on the fruits of native koa and a„ali„i,
as well as the nonnative formosa koa. Adult females lay their eggs (about 32 per egg mass) on the
leaves and fruits of these species, where the larvae develop (Johnson et al. 2005). The red and black
larvae develop in five stages for an estimated 38 days. Female koa bugs are estimated to live for
Chapter 4. Refuge Biology and Habitats 4-47