Life Cycle and Synchronization of Nymphal Development of the Mayfly Ephoron shigae in Japan (Ephemeroptera: Polymitarcyidae)

The life cycle of E. shigae, including eclosion, nymphal growth, last instar recruitment and adult emergence, was studied in a Japanese river. The synchronization of nymphal development is discussed. Eggs hatched sporadically from mid-March to early April as determined from continuous sampling of eggs from the river substratum. Nymphs attained the last instar in mid- to late August and emerged in mid-September. Size of nymphs at the time of last instar recruitment decreased gradually as did the size of emerging mayflies. Smaller individuals entering the last instar later developed more quickly and required a smaller number of degree-days to complete the last instar than did larger individuals. Consequently, larval development synchronized during the period between last instar recruitment and adult emergence.     

The biology and life cycle of Nemoura avicularis Morton (Plecoptera)

Data are presented on the biology and life cycle of Nemoura avicularis Morton in a North Wales lake, Llyn Dinas, and in the laboratory. Aspects of egg, nymphal and adult biology are described and discussed. Special attention is given to the early instars. The life cycle in the field was followed for a 2-year period. Eggs hatched during April, May and the first half of June, and growth then continued more or less continuously until late January when the nymphs were fully grown. Emergence, however, did not begin until March, reaching a peak in April and continuing into the early part of May. In the laboratory N avicularis was reared through its life cycle from egg to adult. The results of the present study are discussed in relation to previous research on the biology and life cycle of N. avicularis.     

Life history,diagnosis, and biological aspects of Engytatus varians (Hemiptera: Miridae), a predator of Bactericera cockerelli (Hemiptera: Triozidae)

The life cycle and several life parameters of the zoophytophagous predator Engytatus varians (Distant) (Heteroptera: Miridae), including nymphal growth according to Dyar’s rule, were examined in the laboratory. The egg, nymph (five instars), and adult stages were 9.20, 17.36, and 19.02?d in length, respectively. The growth ratio for nymphs was consistent with Dyar’s rule based on the lengths of the femora of the forelegs, the tibiae and femora of the middle legs, and the antennae. Some biological characteristics of E. varians were also evaluated when the mirid was fed three different diets (B. cockerelli third instars, Sitotroga cerealella Olivier [Lepidoptera: Gelechiidae] eggs, and a mixture of both instars and eggs). The length of the nymphal stage was three days longer on a diet of only S. cerealella eggs than when the mirids were fed the third instars of B. cockerelli only or a mixture of both. The sex ratio was not affected by the type of diet. Nymphs of E. varians consumed B. cockerelli nymphs (80–85) when fed third instars only and third instars?+?S. cerealella eggs, respectively. The potential use of this predator as a biological control agent of B. cockerelli is discussed.     

Ecology of Potamanthus myops (Walsh) (Ephemeroptera: Potamanthidae) in a Michigan stream (USA)

The ecology of Potamanthus myops (Potamanthidae) was examined for a one year period in a central Michigan fourth order stream. Lowest nymphal densities (4.7 m^-2) occurred in mid-summer after adult emergence, while highest densities were found during late summer and fall (68.0 m^-2 and 66.2 m^-2) after the new cohort had hatched. Biomass was the inverse of density with highest values, 67.7 mg m^-2, just prior to peak adult emergence in June and lowest in late summer (16 mg m^-2). Nymphs maintained a contagious spatial distribution with k values ranging between 0.19 and 1.40. P. myops nymphs fed mostly on detritus (96.8%), placing them in the collector-gatherer functional group. Nymphs were always found in erosional zones associated with rock substrate. Nymphs used their mandibular tusks for positioning themselves beneath rocks, while also appearing to use them for defensive purposes.     

Alarm pheromone eliciting attack and escape responses in the sugar cane woolly aphid,Ceratovacuna lanigera (Homoptera,Pemphigidae)

All nymphal stages and apterous adults ofCeratovacuna lanigera secreted droplets containing an alarm pheromone from their abdominal cornicles when stimulated with a pin. When fresh droplets on piece of filter paper were put near the aphids, 1st-instar nymphs originating from apterous adults attacked it, but the advanced instar nymphs and adults escaped from the spot. Nymphs and adults originating from alate adults showed escaping behavior only. These different responses strongly correlated with morphological differences, such as relative lengths of the frontal horns and legs. When a syrphid larva,Allograpta javana, was placed on a colony of aphids, many 1st-instar nymphs attacked it using their frontal horns. During the attack, these nymphs spontaneously secreted droplets and adhered them to the syrphid body. When these droplets were placed on the body, the syrphid larva was agressively attacked by additional 1st-instar nymphs.     

Assessing peridomestic entomological factors as predictors for Lyme disease.

The roles of entomologic risk factors, including density of nymphal blacklegged ticks (Ixodes scapularis), prevalence of nymphal infection with the etiologic agent (Borrelia burgdorferi), and density of infected nymphs, in determining the risk of human Lyme disease were assessed at residences in the endemic community of South Kingstown, RI. Nymphs were sampled between May and July from the wooded edge around 51 and 47 residential properties in 2002 and 2003, respectively. Nymphs were collected from all residences sampled. Tick densities, infection rates, and densities of infected nymphs were all significantly higher around homes reporting Lyme disease histories in 2003, while only infection rates were significantly higher in 2002. However, densities of infected nymphs did not significantly predict the probability of Lyme disease at a residence (by logistic regression) in either year. There were no significant differences in entomologic risk factors between homes with state-confirmed Lyme disease histories and homes with self-reported cases (not reported to the state health department). Therefore, although entomologic risk factors tended to be higher at residences with cases of Lyme disease, entomological indices, in the absence of human behavior measures, were not useful predictors of Lyme disease at the scale of individual residences in a tick-endemic community.     

Interactions of colonisation density and leaf environments on survival of Trioza eugeniae nymphs

1. Female eugenia psyllids Trioza eugeniae oviposit on the margins of expanding young Syzygium paniculatum leaves. The developing nymphs, feeding within pit‐shaped galls on the leaves, cause the leaves to become curled and deformed. The degree of leaf curling was correlated positively with densities of T. eugeniae nymphs. 2. High relative humidity increased persistence of nymphs on leaves at low insect densities, but persistence did not differ between high or low relative humidity conditions when nymphal densities were high and leaves were greatly curled. 3. Direct insolation increased nymphal mortality. Nymphs on the abaxial leaf surface in the direct sun had lower mortality than similarly exposed nymphs on the adaxial leaf surface. 4. Field populations showed high preference for abaxial leaf surfaces and a stronger preference for shaded adaxial surfaces than for exposed adaxial surfaces. 5. Adverse environmental conditions of direct insolation and low relative humidity may be mitigated by leaf curl associated with moderate populations, however competition at high nymphal density supersedes any potential benefit arising from leaf curling and has a negative effect on nymphal survival.     

Effects of temperature on growth rate and behavior of Epeorus albertae (Ephemeroptera: Heptageniidae) nymphs

Anthropogenic disturbances affect temperature in river systems. Temperature potentially affects life histories of macroinvertebrates and alters behavior and biological functions. Temperature preferences and tolerance ranges for key taxa are therefore critical for understanding impacts of human-induced changes to water temperatures on river ecosystems. The objective of this study was to examine the effect of water temperature on growth rate and behavior of Epeorus albertae (McDunnough) nymphs. Nymphs were collected from the Umatilla River in eastern Oregon, and exposed to temperatures of 18, 22, and 28 °C. Nymphs held at 28 °C exhibited increased growth rates compared with individuals held at 18 and 22 °C. However, at 28 °C the accumulation of nymphal tissues was not consistent with that of nymphs held in lower temperatures; ratios of head capsule width to total body length were significantly lower in individuals at 28 °C compared with those held at the lower temperatures. This indicates that the nymphs held at the high temperature had longer total body length relative to the developmental stage, represented by head capsule width, when compared with insects in cooler temperatures. To examine the effect of water temperature on behavior, active drift of mayflies was examined in experimental chambers held at 12, 18, 22, and 28 °C. The number of drifting insects observed was significantly higher at 28 °C compared with 22, 18, and 12 °C. These results indicate that temperature is a factor influencing growth and behavior of E. albertae and is likely to lead to limitations in habitat use of this mayfly.     

Living Apart Together: On the Biology of two Sympatric Leuctra Species (Plecoptera,Leuctridae) in an Apenninic Stream,Italy

Leuctridae is the richest stonefly family on the European continent, with many species of Leuctra often coexisting in sympatry in the same lotic environment. In this work we studied the life cycle and feeding habits of two species, Leuctra fusca and L. hippopus, coexisting in a small Italian Apennine stream. The life cycles of the two species are non‐overlapping, i.e., periods of nymphal growth and adult emergence are separated. Nymphs of both species feed mainly on detritus, but quantities of coarse particulate organic matter (CPOM) and diatoms are also ingested. Larger nymphs of both species ingest more CPOM and fewer diatoms. This suggests a similar trophic behaviour through their development. For example, they act as collector‐gatherers in their earlier instars and as collector‐gatherers or as shredders in their later instars (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Notes on paternal care and sibling cannibalism in the giant water bug, Lethocerus deyrolli (Heteroptera: Belostomatidae)

Males of the giant water bug, Lethocerus deyrolli, care for egg masses on vegetation above the water surface. They supply the developing eggs with water and guard them against predators. In the present study, mechanisms by which paternal care is extended were found. Males were found situated just below the water on the natal substrate (usually a stick), and the first instar nymphs were aggregated around the substrate. When disturbed, the males showed aggressive behavior, threatening the intruder with their forelegs. Nymphs up to 12 h old did not attack the offered sibling nymphs or anuran larvae, which are common prey in the field. The 24 h‐old nymphs attacked both prey animals; however, they preferred anuran larvae. Cannibalistic behavior in the nymphs was well developed 72 h after hatching, when the nymphs had already dispersed from the natal substrate. The suppression of sibling cannibalism in younger nymphs would promote the maintenance of tight nymphal aggregations and consequently extend male care in this predatory species.     

Life cycle and production of Skwala parallela (Frison) (Plecoptera: Perlodidae) in a Colorado montane stream

The life cycle and production of Skwala parallela, a perlodid stonefly, was investigated in a third-order Colorado montane stream. The species exhibited a univoltine life cycle with a distinct cohort. Small nymphs appeared in May. Rapid growth was exhibited throughout summer and autumn. During winter, growth slowed somewhat but was continuous until April. Maximum density of 34 nymphs/m² occurred in July. Based upon the instantaneous growth method, annual production was 395.3 mg/m² or 3.95 kg/ha dry weight with a P/B ratio of 4.4     

Parasitism of lizards by immature stages of the blacklegged tick,Ixodes scapularis (Acari,Ixodidae)

From 1982–1985 and 1993–1999, a total of 309 individual reptiles, mostly lizards and snakes, belonging to 12 species (American alligator, six lizard species, five snake species) was captured on St. Catherine's Island, Liberty County, Georgia, USA, and examined for ticks. Three lizard species, the broad-headed skink Eumeces laticeps, southeastern 5-lined skink Eumeces inexpectatus, and eastern glass lizard Ophisaurus ventralis, were severely infested with larvae and nymphs of the blacklegged tick, Ixodes scapularis. Ticks were not found on any of the other reptile species. Overall, 80% of 65 E. inexpectatus examined were parasitized by a mean intensity of 21.5larvae and 88% were parasitized by a mean intensity of 4.8 nymphs. Corresponding figures for E. laticeps (n=56) were 93% and 51.3 for larvae and 89% and 7.4 for nymphs, and for O. ventralis (n=3) were 67% and 22.5 for larvae and 100% and 21.3 for nymphs. Larvae and nymphs attached along the lateral grooves of O. ventralis. Nymphs attached mainly behind the ears and in the foreleg axillae whereas larvae mainly attached to these sites and on the hindlegs in Eumeces spp. Seasonally, both larvae and nymphs were recorded on lizards from April through October. A unimodal larval peak was recorded in May or June. Seasonal data for nymphs did not reveal any distinct peaks but small bimodal peaks in mean intensities may have occurred (one in early summer, the other in late summer)suggesting that some ticks complete their life cycle in one year, and others in two years, on St. Catherine's Island. Potential epidemiological consequences of these findings with respect to Lyme disease in the southeastern United States are briefly addressed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Life Cycle,Feeding and Production of Isoptena serricornis(Pictet, 1841) (Plecoptera,Chloroperlidae)

Some aspects of the biology and ecology (life cycle, feeding and production) of a population of Isoptena serricornis in the Rudava River (Slovakia) are studied, reported and discussed. The life cycle is annual, with slow growth in autumn‐winter and fast growth in late summer and spring. The growth decreased two weeks before the Fall Equinox and increased two weeks after the Spring Equinox. The flight period spans from the end of May to the beginning of July. The presence of large sand particles in the gut of all studied nymphs is of note, and indicates that I. serricornis acts as a deposit‐collector species. Nymphal food is principally composed of detritus, unicellular organisms and, in nymphs of intermediate or large size, Chironomidae larvae. Adult food is composed fundamentally of different types of pollen grains. Males usually have lower food content than females. Annual production of this species (∼694–750 mg · m⁻²) is very high in relation to other previously studied Chloroperlidae. This is probably largely responsible for I. serricornis being one of the most abundant components of the macroinvertebrate community in its habitat in the Rudava River. A negative correlation between production and temperature was observed.     

The role of amphibian prey in the diet and growth of giant water bug nymphs in Japanese rice fields

Predatory insects that depend upon particular prey animals are commonly regulated by the prey animal’s abundance. Nymphs of the giant water bug Kirkaldyia (=Lethocerus) deyrolli (Heteroptera: Belostomatidae) are predators regarded as specialists in feeding on tadpoles. We studied the ontogenetic diet shift of aquatic nymphs by quantifying instar abundance and by analyzing captured prey and prey relative abundance during the period of rice irrigation in three localities. We also evaluated the contribution of major prey items (tadpoles, frogs, and Odonata nymphs) on specific growth rates of each nymphal stage in a rearing experiment. First to third-instar nymphs of K. deyrolli fed mainly on tadpoles, regardless of differences in prey availability. Nymphs of subsequent fourth and fifth instar stages shifted from tadpoles to other prey animals within each rice field. A rearing experiment demonstrated that giant water bug nymphs provided with tadpoles had greater specific growth rates at all nymphal stages, except for the final stage, than nymphs fed other prey (frogs and Odonata nymphs). The emergence of young K. deyrolli nymphs seemed to coincide with the period during which tadpoles became abundant in the rice fields. Consumption of tadpoles seems important to allow the nymph to complete its larval development in an unstable temporary habitat. An erratum to this article can be found at     

Do nymphs of Parameletus chelifer and P. minor (Ephemeroptera) reduce mortality from predation by occupying temporary habitats?

Summary The possible effect of predation on the habitat selection of nymphs of the two mayfly species Parameletus chelifer Bengtsson and P. minor (Bengtsson) was investigated for different habitats of a North Swedish boreal river. In spring, these two species migrate to river margins and subsequently, in different proportions, to adjacent seasonal ponds. Feeding rates on mayfly nymphs and mosquito larvae by some dytiscid beetles and larvae, a corixid waterbug and a caddisfly larva were studied in the laboratory. In the seasonal pond, the consumption rate of invertebrate predators on Parameletus nymphs was below that expected from their relative abundance, and mosquito larvae were preferred. At the river margin, where mosquito larvae were absent, Parameletus nymphs were consumed in agreement with their relative abundance. The absolute abundance of macroinvertebrate predators was similar at the river margin and in the pond. Fish predators visited the seasonal pond only during a short time of flood, while at the river margin their presence was continuous. In the seasonal pond, minnow and roach consumed nymphs of both P. chelifer and P. minor in a lower proportion than expected. At the river margin, nymphs of P. chelifer were consumed by minnow and ten-spined stickleback in a higher proportion than expected. Nymphs of P. minor were consumed according to expectance. Imagines of P. minor emerged early, and nymphs were equally abundant in the river and in the seasonal pond. In contrast, almost all nymphs of P. chelifer migrated to the seasonal pond. The later emergence of P. chelifer would probably result in a very high mortality from predation if it remained at the river margin.     

Life cycle,nymphal feeding and secondary production of Dinocras cephalotes (Plecoptera) in a Mediterranean river

Summary. Some aspects of the life history of a population of Dinocras cephalotes inhabiting a Mediterranean river in Southern Spain were studied over a year (2012–2013). The life cycle of this population seems to be semivoltine, of approximately two years of duration, and with an asynchronous egg hatching period. The comparison of these data with those of an unpublished study carried out in the same population almost a decade before (2004–2005) shows the existence of no differences between years. The nymphal feeding study revealed that the main prey of these organisms are Chironomidae, Psychomyiidae and Baetidae, but some of them, usually the smallest, also had non-animal matter in their guts, mainly detritus, coarse particulate organic matter and algae. So, an onthogenetic shift in feeding was detected. This feeding confirms broadly what was already reported in previous studies in the same and other populations. Finally, and for the first time for this species, the secondary production was estimated. Due to differences in hatching, and so development, among nymphs, annual secondary production was calculated both assuming a CPI of 20 months and a CPI of 14 months. In both cases this value was relatively high, 2854.46 and 4077.80 mg DW m^–2 year^–1, respectively. These results were compared with those of other predators, and particularly with a stonefly predator with a similar life cycle and from a nearby temporal river.     

Influence of harmonic radar tag attachment on nymphal Halyomorpha halys mobility,survivorship, and detectability

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a polyphagous invasive insect and currently one of the most threatening agricultural pests in the USA and globally. Nymphs are highly mobile, moving among host plants, and causing significant damage. Thus, understanding dispersal biology for all life stages is critical for the development of reliable monitoring and management programs. Here, we evaluated the influence of harmonic radar as a tool to study dispersal ecology of nymphal H. halys; we measured the impact of glues and tag attachment on survivorship and mobility in the laboratory and validated in the field that tagged and released nymphs could be tracked on baited and unbaited host and non‐host plants using harmonic radar. In the laboratory, four glues were evaluated for attaching harmonic radar tags securely to nymphs, and survivorship with attached tags was measured. There were no significant differences in survivorship or vertical and horizontal movement among nymphs with tags affixed with the glue treatments compared with the untagged control. Based on numerically greater survivorship of nymphs with tags affixed with Loctite glass glue, a field validation study of tagged nymphs released in host (apple tree) and non‐host (mowed grass) with or without H. halys pheromonal stimuli present revealed that nymphs could be successfully relocated using harmonic radar after 48 h. Among treatments, 83% of nymphs remained in baited and unbaited apple trees, 50% of nymphs remained in baited mowed grass plots, and in unbaited mowed grass plots, 17% of fifth instars, and 0% of fourth instars were retained. The absence of negative effects on mobility, survivorship, and field tracking validates that harmonic radar can be used to study dispersal ecology of nymphal H. halys.     

Infestation and seasonal activity of Ixodes vespertilionis Koch, 1844 (Acari: Ixodidae) on the Maghreb mouse‐eared bat,Myotis punicus Felten, 1977, in northeastern Algeria

Infestation of Ixodes vespertilionis Koch, 1844 on Myotis punicus Felten, 1977 from two sites (Trios Tunnel and Sidi Trad cave) in northeastern Algeria was studied. An overall infestation of 41.4% for all stages was found among bats collected from both sites. By stage, a total of eight females, 70 nymphs, and 107 larvae were recovered from both populations. The number of females recovered per bat at Sidi Trad ranged from 0‐1, for nymphs 0‐2, and for larvae 0‐2. While no female ticks were collected at Trios Tunnel, the number of nymphs ranged from 0‐2 and for larvae 0‐2. At Trios Tunnel, the number of nymphs was significantly higher during April and June but not for July and September. On the other hand, the number of larvae increased from July to November, while at Sidi Trad cave, female ticks were recovered during April and May and then disappeared until the end of the study period. Significant differences were noted during all the months when compared with all stages. Nymphs infested bats significantly during April and May, declined in June and July, and then became steady until October. Larvae peaked in July, with low frequency in April, and then fluctuated from August to November.     

Influence of nymphal size, sex and morphotype on microdistribution of Deleatidium (Ephemeroptera: Leptophlebiidae) in a New Zealand river

• 1 The interaction of water depth and velocity with size, sex and morphotype of nymphs belonging to the leptophlebiid mayfly genus Deleatidium was investigated in a New Zealand river.
• 2 Velocity had a significant effect on distribution such that larger nymphs tended to be found more commonly in faster water. Depth also influenced size distribution, but in different ways at different sites.
• 3 Water velocity or depth alone did not significantly influence the distribution of sexes (1.0 mm head width), but the combined effect of these two factors was significant. Final instar males appeared to be relatively more abundant in slower water than final instar females.
• 4 Nymphs (1.0 mm head width) belonging to the informal lillii group (apically pointed gills) were present over a wide range of depth and velocity conditions, but those belonging to the myzobranchia group (round-tipped gills) were largely restricted to fast water (>0.9ms^?1).
• 5 Several mechanisms thought to cause variations in microdistribution are discussed. These include differential effects of oxygen availability, food requirements and drag forces, nymphal behaviour, and selection of oviposition sites by adults.