EJE, vol. 96 (1999), issue 2

Proceedings of the Third European Workshop of Invertebrate Ecophysiology


Eur. J. Entomol. 96 (2): 1999


Life cycles in polar arthropods - flexible or programmed?


Eur. J. Entomol. 96 (2): 83-102, 1999

Climate features that influence life cycles, notably severity, seasonality, unpredictability and variability, are summarized for different polar zones. The zones differ widely in these factors and how they are combined. For example, seasonality is markedly reduced by oceanic influences in the Subantarctic. Information about the life cycles of Arctic and Antarctic arthropods is reviewed to assess the relative contributions of flexibility and programming to life cycles in polar regions. A wide range of life cycles occurs in polar arthropods and, when whole life cycles are considered, fixed or programmed elements are well represented, in contrast to some...

Species at the edge of their range: The significance of the thermal environment for the distribution of congeneric Craspedolepta species (Sternorrhyncha: Psylloidea) living on Chamerion angustifolium (Onagraceae)


Eur. J. Entomol. 96 (2): 103-109, 1999

There is much current discussion about the factors that control the distribution and abundance of animal species, particularly at the edges of their range. The significance of temperature for survival and development is compared in two closely related psyllid species (Craspedolepta nebulosa and C. subpunctata) living on the same host plant (Chamerion angustifolium) (Onagraceae) but displaying different distributions along latitudinal and altitudinal gradients. The following measurements were made at critical periods during the life cycle (a) winter supercooling points (SCPs), (b) tolerance of short (1 min) and long term (1-25)...

Periods of dormancy and cohort-splitting in the millipede Polydesmus angustus (Diplopoda: Polydesmidae)


Eur. J. Entomol. 96 (2): 111-116, 1999

First stadium juveniles of P. angustus were reared under controlled seasonal conditions to maturity, reproduction and death. Individuals born in any one breeding season either had a 1-year or a 2-year life cycle (cohort-splitting). The life cycle was annual for individuals born in the first part of the breeding season (May-August), but became biennial for those born later (August-October). Two phenomena were involved: (1) Only individuals reaching the penultimate stadium (stadium VII) before a critical period at the end of spring could become adult in the breeding season following that of their birth. After this time, stadium VII individuals...

Site latitude influences on the respiration rate, fat content and the ability of worker ants to rear larvae: A comparison of Myrmica rubra (Hymenoptera: Formicidae) populations over their European range


Eur. J. Entomol. 96 (2): 117-123, 1999

Myrmica rubra is a northern, temperate Palaearctic ant species with a geographical range that extends from the Atlantic coast of Europe to central Asia. In Europe, its range covers > 25 of latitude where it lives under a variety of climates that vary from extreme oceanic in the west, to continental in the east. Colonies nest in the soil and their life cycles are known to be highly dependent on ambient temperature and soil moisture. We hypothesised that the brood-rearing behaviour of populations might be focally adapted to climate and that we might detect differences when the ants were reared under \"common-garden\" conditions. Brood-rearing...

Clonal variability in sequences of morph production during the transition from parthenogenetic to sexual reproduction in the aphid Rhopalosiphum padi (Sternorrhyncha: Aphididae)


Eur. J. Entomol. 96 (2): 125-133, 1999

Winter climate determines the success of the two main reproductive strategies employed by aphids. Permanent parthenogens survive as parthenogenetic females in mild winters, but are regularly eliminated by low temperatures; while cyclical parthenogens, which switch to sexual reproduction by the end of summer, produce every year fertilised diapausing eggs resistant to frost.

We have studied the variation in sexual morph production of several clones of the cereal aphid Rhopalosiphum padi (L.) showing both strategies. Twenty clones of this species differing by their geographic origin and their mode of reproduction were placed in two laboratory...

Host-plant mediated influences on population development of Sitobion avenae (Sternorrhyncha: Aphididae)


Eur. J. Entomol. 96 (2): 135-141, 1999

We investigated the effects of genetic differences and host plant density on population development of the rose-grain aphid Sitobion avenae (F.) (Sternorrhyncha: Aphididae) in winter wheat stands. Aphid numbers on ears were recorded on 11 cultivars (6 years) and on plots where crop density was varied by thinning (12 years). Crop density significantly affected whole plant, tiller and ear mass, number of tillers, and leaf area and chlorophyll content. The duration and rate of aphid population growth, and the maximum numbers of aphids were ascertained by weekly counts. Maximum abundances increased with the length of time available for the growth...

Comparison of development and growth of nettle-feeding larvae of Nymphalidae (Lepidoptera) under constant and alternating temperature regimes


Eur. J. Entomol. 96 (2): 143-148, 1999

Mean development rates under cycling temperature regimes (both alternating and sinusoidal regimes) have been found to be either accelerated, decelerated or unaffected when compared to development at constant temperature regimes with equivalent means. It is generally accepted that this phenomenon is a consequence of the non-linearity inherent in the temperature-rate relationship of insect development and is known as the rate summation, or Kaufmann, effect. Some researchers invoke an additional physiological mechanism or specific adaptation to cycling temperatures resulting in a genuine alteration of development rate. Differences in development rates...

Impacts and responses at population level of herbivorous insects to elevated CO2


Eur. J. Entomol. 96 (2): 149-156, 1999

Most studies of responses of insects to elevated carbon dioxide have been made using short-term exposures to treated food plants and have involved measurements of responses in growth, reproduction, food consumption and efficiencies of conversion at specific stages in the life cycle. These will be reviewed in the light of longer-term studies recently published where whole generations have been reared in chambers with simultaneous treatment of plants and where insects have been free to select their food and microenvironment. Factors such as seasonal change in plants, choice of food plant, mode of feeding, timing of exposure, temperature, the role of...

Insect cold tolerance: How many kinds of frozen?


Eur. J. Entomol. 96 (2): 157-164, 1999

Insect cold tolerance mechanisms are often divided into freezing tolerance and freeze intolerance. This division has been criticised in recent years; Bale (1996) established five categories of cold tolerance. In Bale's view, freezing tolerance is at the extreme end of the spectrum of cold tolerance, and represents insects which are most able to survive low temperatures. Data in the literature from 53 species of freezing tolerant insects suggest that the freezing tolerance strategies of these species are divisible into four groups according to supercooling point (SCP) and lower lethal temperature (LLT): (1) Partially Freezing Tolerant-species that survive...

Chill injury at alternating temperatures in Orchesella cincta (Collembola: Entomobryidae) and Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)


Eur. J. Entomol. 96 (2): 165-168, 1999

Survival and Lt50 after exposures at constant low temperature were compared to the values obtained at alternating temperatures in two active (summer acclimated) temperate terrestrial arthropods. The experimental regimes used interruptions - daily transfers from the lower temperature to various higher temperatures for two hours or to one high temperature for Various durations. In both species the alternating conditions improved survival, implying reparation of the chill injury. In the collembolan Orchesella cincta, there was a maximum Lt50 when the higher exposure temperature was equal to the temperature of rearing (19C)....

Temperature, development and establishment potential of Thrips palmi (Thysanoptera: Thripidae) in the United Kingdom


Eur. J. Entomol. 96 (2): 169-173, 1999

In order to manage the risks posed to domestic crop production by quarantine pests such as Thrips palmi, their potential to establish in a new environment must be assessed. The thermal requirements for development of T. palmi were determined and compared with UK temperatures, to estimate its potential for development under UK conditions. Temperature and rate of development of T. palmi from egg to adult were linearly related between 15 and 30C, allowing calculation of an overall threshold of 10.1C, and a sum of effective temperatures of 194 degree-days. In the UK, development of T. palmi would be possible outdoors during...

Cold tolerance strategy of the freeze-intolerant chrysomelid, Aulacophora nigripennis (Coleoptera: Chrysomelidae), in warm-temperate regions


Eur. J. Entomol. 96 (2): 175-181, 1999

We investigated the physiological adaptations for winter survival in a freeze-intolerant chrysomelid, Aulacophora nigripennis, in warm-temperate regions. The adults showed a decreased supercooling point (SCP), increased chill tolerance and high myo-inositol content during winter. Chill tolerance at 0C appears to be a more suitable indicator of their cold hardiness than SCP because they die at 0C without freezing and normally an not exposed to subzero temperatures below their SCP (

Cold hardiness in diapause and non-diapause larvae of the summer fruit tortrix, Adoxophyes orana (Lepidoptera: Tortricidae)


Eur. J. Entomol. 96 (2): 183-187, 1999

Cold hardiness of larvae of the summer fruit tortrix moth, Adoxophyes orana (Fischer von Rosslerstamm) (Lepidoptera: Tortricidae) was examined in the laboratory. Supercooling point of field collected larvae increased significantly from a mean value of -23.9C in February 1998 to -16.9C in June 1998. Mean supercooling points for laboratory diapause and non-diapause larvae were -20.7C and -17.2C respectively. Short period of acclimation (10 days at 0C) significantly decreased supercooling point to -24.7C for laboratory diapause larvae. Acclimation for 12 days at 5C decreased supercooling point to -19.4C for non-diapause larvae. Pre-freeze...

The influence of thermal acclimation on the amylolytic activity and microanatomy of the alimentary tract of the oribatid mite Galumna elimata (Acari: Oribatei)


Eur. J. Entomol. 96 (2): 189-198, 1999

The oribatid mite Galumna elimata was reared under laboratory conditions on algae (Protacoccus spp.) at different temperatures (5, 15 and 20C). Higher weight-specific amylolytic activity was found in the whole body homogenates of mites exposed to cold acclimation (5C, 21 days) in comparison with individuals acclimated to 15 and 20C. Accompanying parameters (live body weight, content of total soluble proteins in the body, protein-specific amylolytic activity, presence and composition of food boluses, activity of mesenteric and caecal wall cells, gregarinid parasitisation, number of glycogen granulae and guanine deposits in mesenchymal...

Desiccation stress and recovery in the anhydrobiotic nematode Ditylenchus dipsaci (Nematoda: Anguinidae)


Eur. J. Entomol. 96 (2): 199-203, 1999

The plant-parasitic nematode Ditylenchus dipsaci shows a delay in recovery following a period of desiccation and reimmersion in water. This delay, called the \"lag phase\", has been shown to be related to the severity of desiccation. It is the severity of the desiccation stress during dehydration, rather than the final relative humidity to which the animal is exposed which determines the length of the lag phase. A lag phase appears even after a brief exposure to desiccation. These results indicate that a period of repair, or the restoration of a normal physiological state, must be undertaken before activity can resume.

Intertidal respiration of Anurida maritima (Collembola: Neanuridae)


Eur. J. Entomol. 96 (2): 205-209, 1999

The intertidal collembolan Anurida maritima can endure periods of twice-daily submergence by seawater. The air-breathing terrestrial apterygote insect has developed specific adaptations to prevent respiratory failure during hypoxic stress. When submerged, the animal is initially enclosed by an air-bubble. This bubble lasts three times longer than the small amount of stored oxygen would allow. The air bubble acts not only as an oxygen store but also as a compressible gas gill. This was demonstrated by an O2-needle electrode technique which allowed recordings of pO2 changes in the watery medium close to the animal. Oxygen...