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INTERNATIONAL JOURNAL OF ENTOMOLOGY International Journal of Entomology Vol. 26, no. 1-2: 1-128 29 March Published by Department of Entomology, Bishop Museum, Honolulu, Hawaii, USA. Editorial committee: JoAnn M. Tenorio (Senior Editor), G.A. Samuelson & Neal Evenhuis (Co-editors), FJ. Radovsky (Managing Editor), S. Asahina, J.F.G. Clarke, K.C. Emerson, R.G. Fennah, D.E. Hardy, R.A. Harrison, J. Lawrence, H. Levi, T.C. Maa, J. Medler, CD. Michener, W.W. Moss, CW. Sabrosky, J J.H. Szent-Ivany, I.W.B. Thornton, J. van der Vecht, E.C Zimmerman. Devoted to original research on all terrestrial arthropods. Zoogeographic scope is worldwide, with special emphasis on the Pacific Basin and bordering land masses. © 1984 by the Bishop Museum PSOCOPTERA OF THE HAWAIIAN ISLANDS Part III. The endemic Ptycta complex (Psocidae): Systematics, distribution, and evolution Ian W. B. Thornton1 Abstract. A complex of 51 psocopteran species of the genus Ptycta is reported as endemic to the Hawaiian Islands. Thirty-nine species are newly described and redescriptions provided for 12 others. Eleven species groups are recognized and characterized, and a key to species groups is provided. A cladogram based on apomorphies of species groups is constructed, and their archi­ pelago distribution is related to this. Analysis of the distribution of the complex shows that the Kauai-Oahu strait has been the greatest barrier to distribution oi Ptycta species in the island group, 2 species groups being confined to Kauai. It is suggested that a section of the genus with a strong synapomorphy, containing 21 species in 5 species groups, arose in recent geological time on the Maui complex of islands; that it derived from a Kauai source; and that it has not been able to reinvade Kauai. Isolating factors for these insects in the present high Hawaiian Islands are re­ viewed, the geological history of the whole Hawaiian-Emperor chain is discussed, and it is con­ cluded that the Ptycta complex may represent the end results of evolutionary processes acting over a period well in excess of the 5 million years since Kauai, the oldest of the present high islands, arose. This is the 3rd part of a series treating the Psocoptera of the volcanic, oceanic Hawaiian Islands. The fauna is remarkable, comprising some 42 nonendemic species in 20 genera (Thornton 1981c) and over 200 species in 3 endemic complexes: 2 of elipsocid genera (Kilauella Enderlein and Palistreptus Enderlein) and 1 of the genus Ptycta Enderlein (family Psocidae), with which this paper is concerned. Thus, the fauna is of interest not only to specialist entomologists but also to biogeographers, island biologists, and students of island and archipelagic evolution. Some psocopterans (or psocids) are domestic and stored products insects, and some others occur in nature in leaf litter and on the surfaces of dead leaves, rocks, timber and straw, for example, which support the microepiphytes on which they feed. Most, however, and all the Hawaiian endemic species, are found on trees and shrubs. I made preliminary collections on Oahu and Hawaii in 1961, collected extensively on Kauai, Oahu, Molokai, Lanai, Maui and Hawaii (Fig. 1) throughout 1963, and made small collections on Oahu, Molokai and Maui in 1982. I have also had at my 1. Department of Zoology, La Trobe University, Bundoora, Victoria, Australia, 3083. 2 International Journal of Entomology Vol. 26, no. 1-2 155°w -22°N <? : NIIHAU KAUAI MOLOKAI OAHU'"...-----'''^^!^^"^ PuuKuku .._ Haleakala .MAUI N LANA'f KAHOOLAWE Mauna Kohala—7 Kea 100 km. I 1 19UN- 160w HAWAII FIG. 1. Hawaiian Is (main or windward group), to show main volcanoes. Contours at 300 m below sea level (dotted), 500 m, 1600 m, 2000 m, and 4000 m elevation. disposal the considerable collections of other workers (see Thornton 1981c for de­ tails). The islands of Niihau and Kahoolawe were not visited and no psocopterans are recorded from them. They are privately owned, relatively low and dry, and now support little native vegetation. The former is largely agricultural and the latter has been a bombing range for several decades. On the remaining islands of the main or windward group, collections were made in the lowlands as well as in the highlands of all volcanic massifs. That on West Molokai (Mauna Loa) is relatively low (400 m), dry, and has little native forest. Lanai is largely cultivated, but a remnant of native vegetation persists on its single ridge, which reaches a height of 1027 m. The other islands are less disturbed, but the destruction of lowland forests as a result of agri­ cultural activities and urbanization is almost complete, and the introduction of exotic and domestic (in some cases feral) mammals and plants, together with exotic birds, insects (notably ants), and molluscs has had a great impact on the endemic biota of the islands, including some upland areas. As a result, in some groups one cannot expect to encounter the endemic biota below 350-500 m elevation. The low Northwestern Hawaiian Islands, or leeward chain, have not been visited by psocopteran specialists. These rocks, atolls, reefs, and shoals extend for some 2000 km almost in line WNW from Nihoa, W of Kauai, to Kure Atoll (Fig. 336). Collections made from some of these islands by other workers have been studied, and although 1984 Thornton: Hawaiian Islands Psocoptera: Ptycta complex 3 no endemic species have been discovered, 6 nonendemic species that also occur on the main group have been reported (Thornton 1981c). In temperate areas, psocopterans are often common and sometimes abundant in the forests, although with relatively few species represented. The reverse is often the case in the tropics but here, too, they may be locally common. In Hawaii they do not usually reach the densities encountered, for example, in England; they nevertheless make up an important component of the insect fauna, and Zimmerman (1957) re­ garded them as "among the most numerous of all insects in our forests." Gagne & Howarth (1981) have recently reported on a survey of canopy arthropods ofthe dominant trees {Metrosideros collina and Acacia koa) in the montane tropical rain forest ofthe Kilauea area (1200-1800 m) on the slopes of Mauna Loa on the island of Hawaii (Fig. 1). They found Psocoptera present on every tree sampled. Moreover, in a transect of Mauna Loa extending from the shore to the Metrosideros tree line at 2440 m, Psocoptera occurred at all sampling sites, outranked in absolute numbers all other taxa at most sites above 750 m, and at mid- and high elevations (1200-2440 m) usually outranked all other taxa combined in absolute numbers per sample (Gagne 1979). The sampling method excluded dead branches; this probably precluded the recording of several psocid species (see below). Gagne & Howarth (1981) categorize Psocoptera as saprophages, and they are la­ belled detritivores by Gagne (1979). They are also important primary consumers; although many feed largely on lichens and some take the spores of honeydew molds and sooty molds on the surfaces of leaves and bark, many others feed predominantly on unicellular protococcal algae. Temperate psocids, at least, appear to have diver­ sified into lichen feeders on the one hand and Protococcus and fungal spore feeders on the other (Broadhead & Thornton 1954, Broadhead & Wapshere 1966, Broadhead 1958). In their studies of tropical psocids, Broadhead & Richards (1980) concluded that 2 of 14 species of East African psocopterans were lichenophilous, while the rest were more generalized feeders; 4 species oi Ptycta were included in their study, and none was found to feed on lichen, the main components of their gut contents being fungal spores and Protococcus, along with pollen grains, and, infrequently, bryophyte rhizomes and a multicellular alga. Zimmerman (1948a, 1948b) states that in Hawaii ants, green and brown lacewings, dolichopodid flies, and emesine and reduviid bugs are known to prey on psocopterans, and he believes that psocopterans probably were the principal food source of pred­ ators such as the lacewings before aphids arrived in the Hawaiian Is. The carnivorous caterpillars of several endemic Hawaiian species of the geometrid genus Eupithecia Curtis have been observed catching and feeding on psocids at night (Montgomery 1982). Baldwin (1953) found that psocids were an important prey item for 3 species of drepanidids (endemic Hawaiian honeycreepers) which, as well as feeding on nectar, feed selectively on insects and spiders. On examining crop and some gizzard contents of 63 specimens of Loxops virens (the amakahi), 63 Himatione sanguinea (the apapane), 4 International Journal of Entomology Vol. 26, no. 1-2 and 32 Vestiaria coccinea (the iiwi) collected in the Kilauea area of Hawaii I from 1938 to 1949, Baldwin found psocopteran occurrences in the samples at frequencies of 10%, 41%, and 43%, respectively. S.L. Montgomery (pers, commun.) examined giz­ zard contents of 11, 41, and 3 individuals, respectively, ofthe same drepanidid species collected recently in the same area. He found psocopteran remains in 2 Loxops and 7 Himatione gizzards. I have examined these samples and found all identifiable pso- copterans to be endemic species. Kilauella species were found in gizzards of both honeycreepers; one of the Himatione gizzards contained the remains of at least 6 individuals of 2 species. Ptycta remains were identified in samples from Loxops {Ptycta sylvestris (Perkins) or a species of the oahuensis or haleakalae groups), and Himatione {Ptycta hawaiiensis Thornton). Thus, psocopterans are among the most frequent and numerous arthropods on Hawaiian forest trees and are of considerable ecological importance in being part of a number of food chains. Moreover, the endemic complexes are evidently relatively old components ofthe biota and are likely to have been of importance in the evolution of Hawaiian forest ecosystems. The genus Ptycta is well represented outside Hawaii, particularly in the tropics and subtropics.

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