Table 1 
Comparison of species diversity of some insect families 
at Barrow and Prudhoe Bay. Barrow list after Hurd 
(1957) with additions. Prudhoe Bay specimens 
determined as indicated. 
Barrow Prudhoe Bay 
Diptera: Tipulidae 
Tipula begrothiana Alex. 
Tipula arctica Curtis 
Tipula pribilofensis Alex. 
Tipula diflava Alex 
Tipula besselsi OstenSacken 
Tipula macleani (sp. nov.) Alex. 
Prionocera parii OstenSacken 
Prionocera gracilistyla Alex. 
Nephrotoma /undbecki (Nielsen) 
Pedicia hannai antennata Alex. Pedicia hannai antennata Alex 
Erioptera kluane Alex 
Erioptera forcipata Lundstrom 
Limnophila sp. nov. 
(Det. by R. Gorham) 
Tipula carinifrons Holm. 
Tipula aleutica Alex 
(Det. by C. P. Alexander) 
Prionocera gracilistyla Alex. 
Diptera: Culicidae 
Aedes cataphylla 
Aedes impiger 
Aedes nigripes 
Aedes nigripes 
Diptera: Dolichopodidae (Det. by F. Harmston) 
Dolichopus amnicola 
Dolichopus consanguineus 
Dolichopus obcordatus 
Dolichopus eudactylus 
Dolichopus ramifer 
Dolichopus plumipes 
Dolichopus occidentalis 
Dolichopus aldrichii 
Dolichopus humilis 
Campsicnemus nigripes 
Hydrophorus gratiosus 
Hydrophorus sodalis 
Hydrophorus signiterus 
Hydrophorus fumipennis 
Gymnopternus californicus 
Aphrosylus nigripennis 
Aphrosylus fumipennis 
Aphrosylus praedator 
Raphium tripartitum 
Raphium sp. 
(Det. by K. W. Philip) 
Hydrophorus fumipennis 
Lepidoptera: Pieridae 
Colias palaeno 
Colias hecla 
Colias thula 
Colias nastes 
Lepidoptera: Papilionidae 
Papilio machaon 
(Det. by K. W. Philip) 
Lepidoptera: Lycaenidae (Det. by K. W. Philip) 
Lycaeides argyrognomon 
Agriades aquilo 
Lepidoptera: Nymphalidae 
(Det. by K. W. Philip) (Det. by K. W. Philip) 
Boloria frigga 
Boloria polaris 
Boloria chariclea 
Boloria napaea 
(Det. by K. W. Philip) 
Oenis melissa 
Erebia rossii 
Erebia fasciata 
Boloria frigga 
Boloria polaris 
Boloria chariclea 
Lepidoptera: Satyridae 
(Det. by G. C. Byers and C. P. Alexander) 
Walz 
reaches densities of 250 m? in wetter habitats, 
while Tipula carinifrons \arvae may number 
100 m2 in more mesic habitats. Their biomass 
at such densities may exceed 0.5 g dry weight in 
each case. The density of cranefly larvae was far 
lower in all habitats at Prudhoe Bay than in 
comparable habitats at Barrow (Table 2). The 
greatest density was achieved in the drained lake 
basin (plots 4 and 5); there, as in wet meadow 
habitats at Barrow, Pedicia hannai was the domi- 
nant species. The low density of cranefly larvae 
may explain the low breeding populations or 
absence of such shorebird species as the dunlin 
(Calidris alpina) and pectoral sandpiper (C. 
melanotos) (Norton et al., this volume) which 
prey heavily upon cranefly larvae at Barrow. 
Table 2 
Abundance of cranefly larvae (Diptera: Tipulidae) in 
Prudhoe Bay tundra in 1971 and 1972. 
Plot 1971 1972 Major forms 
1 9.8 m2 i) Tipula 
2 2.0 10.0m* — Prionocera 
3 3.9 5.0 Tipula, Pedicia 
4 17.6 40.2 Pedicia 
5 27.4 39.1 Pedicia 
6 22.3 Pedicia 
7 3.4 Tipula 
MacLean (1973) suggested that the high 
density of cranefly larvae at Barrow may be part- 
ly a result of the causal sequence: 
low temperature — low productivity > pro- 
longed life cycle > overlapping larval genera- 
tions. 
For example, larval development of Pedicia han- 
nai at Barrow requires 4 or 5 years. If the 
warmer summer conditions at Prudhoe Bay 
allow individuals to shorten the life cycle, the 
result would be lower biomass at any one time 
in relation to population productivity. Thus, 
care must be taken in interpreting density and 
biomass values from different sites; howeve;, 
even allowing for possible differences in life 
cycle length, it is clear that productivity of 
craneflies is less at Prudhoe Bay than at Barrow. 
