NEW SPECIES OF JSCHIOSCIA FROM VENEZUELA 
167 

Fig. 26 Distribution of the species of Ischioscia Verhoeff, 1928 in Venezuela. 0, I. guamae; *, I. pariae; @, I. colorata; #, I. trifasciata; @, I. hirsuta; 
+, I. fasciifrons; %, I. variegata. 
even the astonished human collector. The strong pereopods 6 and 7 
with the powerful musculature in the basis are essential for this type 
of locomotion. The jumping capability may provide another 
synapomorphy for the two species. Another strategy to escape 
predators was observed in /. hirsuta. A specimen which was observed 
at the bank of a small brook fled under water and stayed submerged 
for a considerable period. 
These new records widen our knowledge on the genus particu- 
larly with respect to their biogeography. The genus is well-distributed 
in Costa Rica (Leistikow 1999), most records from Venezuela refer 
to the most abundant species /. variegata, which is distributed in the 
areas adjacent to the Caribbean Sea and also in the interior of 
Venezuela along the western Corilleras (Fig.26). The other species 
seem to have more restricted ranges: I. pariae is confined to the 
Peninsula de Paria; /. colorata was found in the vicinity of Districto 
Federal. These patchy distributions may be collection artifacts. But 
they may reflect a characteristic biogeographical pattern found in 
many Neotropical taxa. Cracraft (1985) argued for the generality of 
areas of endemism in South America. It is possible to compare 
distributional data obtained from such diverse taxa as plants (Prance 
1982), butterflies (Whitmore & Prance 1986) or birds (Haffer 1974, 
Cracraft 1985). They all support distinct regions of high endemism 
called Pleistocene refuges by Haffer (1974). The distribution of 
species of /schioscia in Venezuela also corresponds to those regions. 
I. pariae is found in the Parian centre, /. colorata in the Venezuelan 
Montane centre and /.hirsuta in the Meridan Montane centre. The 
widespread /. variegata might be an expansive species best adapted 
to human habitats, although some of the records may be erroneous 
(Arcangeli 1930, Richardson 1914). I. variegata may occur in close 
spatial vicinity of a second species of Ischioscia, but they were not 
encountered in exactly the same locality. Thus, effective isolation 
mechanisms have to be postulated to separate the species. 
ACKNOWLEDGMENTS. The author is grateful to Dr. C. Schmidt for permis- 
sion to analyse the philosciid samples. Moreover, he is indebted to Dr. H. 
Schmalfuss, Staatliches Museum fiir Naturkunde, for the loan of material of 
Ischioscia from the museum’s collection. 
REFERENCES 
Arcangeli, A. 1930. Contributo alla conoscenza del ‘Microgenton’ di Costa Rica. 
Bollettino del Laboratorio di Zoolgia Agraria della Faccolta Agraria 25: 1-29. 
Cracraft, J. 1985. Historical biogeography and patterns of diversification in Neotropical 
birds. Ornithological Monographs 36: 49-84. 
Haffer, J. 1974. Avian speciation in tropical South America. Publications of the Nuttall 
Ornithological Club 14: 1-196. 
Leistikow, A. 1997. Terrestrial Isopods from Costa Rica and redescription of Ischioscia 
variegata (Dollfus, 1893). Canadian Journal of Zoology 75: 1415-64. 
