Relations of intraspecific variations in fecundity, clutch size, and oviposition frequency to the body size in three species of stoneflies, Sweltsa sp., Isoperla aizuana, and Stavsolus japonicus

Most stoneflies oviposit several times during their adult stage. In this study, the relations among oviposition frequency, the number of eggs per egg mass, and body size were examined in the chloroperlid stonefly Sweltsa sp. and two perlodid stoneflies, Isoperla aizuana and Stavsolus japonicus. It was found that larger individuals tended to oviposit more frequently than smaller ones, but the relation was significant only in Isoperla aizuana. In Sweltsa sp. and Isoperla aizuana, the number of eggs per egg mass was higher for the less-frequently ovipositing individuals than for those ovipositing more frequently, and the number of eggs per egg mass decreased with successive oviposition events. Stavsolus japonicus showed the same tendency but it was not statistically significant.     

Stable isotopes identify dispersal patterns of stonefly populations living along stream corridors

1. Populations in different locations can exchange individuals depending on the distribution and connectivity of suitable habitat, and the dispersal capabilities and behaviour of the organisms. We used an isotopic tracer, ¹⁵N, to label stoneflies (Leuctra ferruginea) to determine the extent of adult flight along stream corridors and between streams where their larvae live. 2. In four mass, mark‐capture experiments we added ¹⁵NH₄Cl continuously for several weeks to label specific regions of streams within the Hubbard Brook Experimental Forest, NH, U.S.A. We collected adult stoneflies along the labelled streams (up to 1.5 km of stream length), on transects through the forest away from labelled sections (up to 500 m), and along an 800‐m reach of adjacent tributary that flows into a labelled stream. 3. Of 966 individual adult stoneflies collected and analysed for ¹⁵N, 20% were labelled. Most labelled stoneflies were captured along stream corridors and had flown upstream a mean distance of 211 m; the net movement of the population (upstream + downstream) estimated from the midpoint of the labelled sections was 126 m upstream. The furthest male and female travelled approximately 730 m and approximately 663 m upstream, respectively. We also captured labelled mature females along an unlabelled tributary and along a forest transect 500 m from the labelled stream, thus demonstrating cross‐watershed dispersal. 4. We conclude that the adjacent forest was not a barrier to dispersal between catchments, and adult dispersal linked stonefly populations among streams across a landscape within one generation. Our data on the extent of adult dispersal provide a basis for a conceptual model identifying the boundaries of these populations, whose larvae are restricted to stream channels, and whose females must return to streams to oviposit.     

Life History of Bittacomorpha clavipes (Fabricius) (Diptera: Ptychopteridae) in an Ozark Spring,U.S.A.

A population of Bittacomorpha clavipes was studied in an Ozark spring from July 1987- August 1988. Measurement of larval head capsules (N=4,544) showed B. clavipes has four distinct larval instars. Seasonal distribution of immature and adult life stages suggests that this population has an asynchronous, non-seasonal, multivoltine life history with at least three cohorts. First instar larvae and pupae were collected during all months except December through March and December through February, respectively. Adults and larval instars II-IV were collected throughout the year. Larval recruitment generally paralleled adult flight periods, and the presence of adults during all months sampled indicates a correlation with ovipositional periods. The life history documented here for B. clavipes suggests that limiting factors for growth and reproduction are not seasonally dependent for this population.     

Persistence and stability of macroinvertebrate communities in streams of Denali National Park, Alaska: implications for biological monitoring

1. Macroinvertebrate communities were studied from 1994 to 2001/2002 (except 1997) in six streams in Denali National Park, interior Alaska. All six streams were potential reference streams with no known impairment. 2. Abundance of individual taxa varied markedly from year to year. Overall, abundance decreased over the study period, particularly with respect to mayflies. Stonefly taxa showed lower persistence and were sometimes absent from a stream in any particular year. 3. Mean community persistence for the six streams, as measured by Jaccard's similarity coefficients between years, varied from 0.48 in the year pair 1999–2000 to 0.78 in 1998–99. Tattler Creek (a small stable stream) supported the most persistent macroinvertebrate community and Highway Pass Creek (a small, unstable creek) the least. Mean community persistence showed a significant relationship with mean winter snowfall (November to March) for the six streams. 4. The highest community compositional stability was found in Tattler Creek and the lowest in Highway Pass Creek, but stability varied markedly over time for the six streams, peaking in 1994–95 and reaching a minimum in 2000–01. Compositional stability was significantly related to the Pfankuch Index of channel stability. 5. The composition metrics % Chironomidae, % dominant taxa, %EPT, % Ephemeroptera and % Plecoptera, employed as part of the Alaska Stream Condition Index, varied over almost their entire range in these pristine streams across the 9 years of the study. 6. This study demonstrates the wide range of natural variation that occurs in benthic macroinvertebrate communities in these pristine central Alaskan streams, potentially limiting the applicability of composition metrics for the biological monitoring of water quality in these systems.     

The pseudoscorpions of New Zealand,Norfolk, and Lord Howe

Nearly 20 000 specimens of pseudoscorpions from a full range of habitats have been examined. For New Zealand, 70 species and subspecies in 28 genera are recognised, and for Norfolk and Lord Howe Islands, 11 species in 9 genera. Endemism is very high in this area: in New Zealand, 13 out of 25 indigenous genera are endemic; 2 others (Apatochernes, Nesochernes) are shared with Norfolk Island; and 4 (Sathrochthonius, Austrochthonius, Synsphyronus, Protochelifer) extend their distribution to Australia (Austrochthonius is known also from South America and South Africa). The rest of the native genera have a wider distribution in the Pacific. Three species (Lamprochernes savignyi, Withius subruber, Chelifer cancroides) have a wide and disjunct distribution induced by human traffic, and are considered to be an introduced element.     

A wingless alpine stonefly from New Zealand,and further information on genus Holcoperla (Plecoptera: Gripopterygidae)

Abstract

Holcoperla magna n.sp. is described and figured from material collected on Headlong Peak, Mt Aspiring National Park. New information is given on H. angularis (Wisely) and H. jacksoni McLellan, and the 3 species are compared. Larvae designated as type specimens of H. angularis are shown to be Apteryoperla monticola Wisely.     

A New Species of Thraulodes (Ephemeroptera: Leptophlebiidae) from Mexico

A new species of Thraulodes from Mexico is described from male and female imagines. The male imagines of this species have very characteristic genitalia that allow its easy separation from the other known species of the genus.     

REPLY TO “COMMENT ON MARDEN (2013) REGARDING THE INTERPRETATION OF THE EARLIEST TRACE FOSSIL OF A WINGED INSECT”

Benner, Knecht, and Engel have replied to my critique of their interpretation of a Carboniferous trace fossil produced by an insect at the edge of water. Here I respond by pointing out that their reiterated scenario still requires mutually exclusive paths of motion and I show that their assertions of methodological shortcomings are tangential and lack merit. Overall, this discussion provides an opportunity to examine in greater detail competing hypothesis about behaviors and taxonomic identity of the trace maker, and relevance thereof to competing theories regarding early events in the evolution of pterygote insects.     

Life cycles and nymphal feeding of Isoperla morenica Tierno de Figueroa and Luzón-Ortega, 2011 and Brachyptera vera cordubensis Berthélemy and Baena, 1984 (Plecoptera: Perlodidae and Taeniopterygidae) in a Mediterranean stream (Spain)

Some aspects of the biology of two endemic Iberian stonefly species, Isoperla morenica Tierno de Figueroa and Luzón-Ortega, 2011 and Brachyptera vera cordubensis Berthélemy and Baena, 1984, were studied in a temporary stream from Sierra Morena (Southern Spain). Isoperla morenica shows a univoltine fast seasonal life cycle, with nymphs growing from November to April. After oviposition, eggs remain in a dormant state in the riverbed until the following autumn when the river water flows again. Nymphal diet is mainly composed of detritus in small individuals (they behave as gatherer–collectors) but when larger, they become predators. Brachyptera vera cordubensis also shows a univoltine fast seasonal life cycle, from November to March. Nymphs behave mainly as gatherer–collector and no significant ontogenetic changes in diet were detected. Male and female nymphs do not show differences in feeding in this species. Data obtained were compared with the previously known information on both species in another stream from the same mountain range as well as for other related species, and some differences in both aspects, mainly on feeding habits, could be detected.