A key to the larvae of Sialidae (Insecta: Megaloptera) occurring in the British Isles

SUMMARY. The discovery of a third species of alderfly ( Sialis nigripes ) in Britain and Ireland necessitates a new larval key for the group in these islands. Characters are now provided to distinguish the larvae of the three species, and their habitat and distribution in the British Isles are outlined.     

A key to larvae and pupae of Sericostoma personatum (Spence) and Notidobia ciliaris (Linné) (Sericostomatidae : Trichoptera) in Britain

SUMMARY. Certain larvae and pupae have been identified as Notidobia ciliaris (Linné) by rearing field-collected larvae to the adult stage and by rearing larvae from eggs laid by a female in captivity. The larvae differ in many important respects from larvae of this species described by earlier workers. Characters are provided to distinguish these larvae and their associated pupae from those of Sericostoma personatum (Spence). The habitat and distribution of both species in Britain is outlined.     

The identification of British limnephilid larvae (Trichoptera)

Fifty–six species of Limnephilidae have been recorded from Britain. Larvae of forty–three species were collected, and the identities of forty–two were confirmed by direct association of individual larvae with their resultant adult stage. Information was obtained on the larvae of twelve more species, leaving the larva of only onespecies, Limnephilus fuscinervis, unknown. A key is provided to the fifth instar larvae of fifty–four species. Limnephilus nigriceps is omitted from the keydue to lack of information. The terminology of morphological characters is reviewed.     

An electrophoretic and morphological study of three Ecdyonurus species (Ephemeroptera: Heptageniidae) occurring in the British Isles

Abstract The objective was to investigate the validity of three closely-related British species: Ecdyonurus dispar, E. venosus and E. torrentis . The species were characterized by eleven enzyme-substrates and fifteen different enzyme-loci, comparisons being made not only between species but also between five populations of E.dispar (three from Britain, one from France, one from Switzerland), two populations of E.venosus and two populations of E. torrentis (one from Britain, one from Switzerland for both species).
Four monomorph enzyme-loci (aldolase, mannose phosphate isomerase, arginine phosphokinase, glutamate-oxaloacetate transaminase-2) exhibited interspecific differences in their mobilities and therefore validated the conclusion that E. dispar, E. venosus and E. torrentis are distinct species. There were no monomorph enzyme-loci that were different between populations of the same species. There were, however, some intraspecific differences revealed by the presence of polymorphic enzyme-loci: seven in E.dispar (retinol dehydrogenase, hexokinase-1 and 2, glutamate-oxaloacetate transaminase-!, malate dehydrogenase-1, phospho-glucomutase, indophenol oxidase-2), three in E. venosus (glutamate-oxaloacetate transaminase-1, malate dehydrogenase-1, phospho-glucomutase) and three in E. torrentis (hexokinase-1, glutamate-oxaloacetate transaminase-1, malate dehydrogenase-1).
The morphological characters of larvae and adults were examined and some were used in new keys to larvae and adults.     

Identification of Dytiscus larvae by cytochrome oxidase I (COI) partial sequencing

Water beetles of the genus Dytiscus are large and conspicuous members of lentic freshwater habitats in much of the Northern Hemisphere. Of the six species found in Britain, four are relatively rare and/or endangered. Conservation of these beetles requires accurate identification during survey and monitoring, which is straightforward for adults. However, larvae can be much more abundant than adults in late spring and early summer and those of all species are morphologically similar. In this paper we describe a relatively simple molecular method, based a short fragment of the mitochondrial cytochrome oxidase I (COI) gene with species-specific sequences that can distinguish all six British Dytiscus. Sampling of larvae in a wetland containing a common (D. marginalis) and a rare (D. dimidiatus) species successfully identified 90 % of the individuals tested whereas morphology-based analysis failed to resolve them. Preliminary phylogenetic analysis based on COI sequences consistently separated D. semisulcatus from the other five species.     

Factors influencing breeding site choice by the pioneering amphibian Bufo calamita

We have investigated environmental factors influencing the choice of breeding pools by Bufo calamita in two different habitat types in Britain, using a number of methods including the construction of artificial pools and the translocation of spawn laid by competitively superior anuran species. On heathland, major determinants were aspects of pond chemistry especially pH, Na and SO₄. On coastal dunes other criteria were important, notably maximum water temperatures achieved the day prior to spawning. These in turn related to the precise shape and size of the pond. In addition, natterjacks were able to discriminate against ponds which already contained large numbers of competitor species Rana temporaria and Bufo bufo larvae. Possible mechanisms underlying site choice by B. calamita are discussed.     

Ecological and taxonomic trends in macrolepidopteran host plant selection

Patterns of host plant use by larvae of macrolepidoptera feeding on trees and shrubs in Britain and Canada are examined. The incidence of polyphagous species varies among different lepidopteran taxa. Among largely monophagous taxa host plant switching has often occurred. The greater similarity of insect faunas on closely related plants is documented using cluster analysis. The Canadian data reveal that lepidopterans feeding on conifers are less specific in their host plant choice than species feeding on angiosperms. The numerical analyses also provide evidence of greater overlap in the insect faunas of plants belonging to the same ecological association. These results are discussed with particular reference to Lepidoptera-plant coevolution.     

Assessing the effects of low temperature on the establishment potential in Britain of the non-native biological control agent Eretmocerus eremicus

Abstract. Eretmocerus eremicus is a parasitoid wasp that is not native to Britain. It is a biological control agent of glasshouse whitefly and has recently been released under licence in Britain for the first time. This study assessed the effect of low temperature on the outdoor establishment potential of E. eremicus in Britain. The developmental threshold calculated by three linear methods was between 6.1° and 11.6 °C, with a degree‐day requirement per generation between 256.3 and 366.8° day^?1. The supercooling points of non‐acclimated and acclimated larvae were similar (approximately ?25 °C). Non‐acclimated and acclimated larvae were subject to considerable pre‐freeze mortality, with lethal temperature (LTemp₅₀₎ values of ?16.3 and ?21.3 °C, respectively. Lethal time experiments indicated a similar lack of cold tolerance with 50% mortality of both non‐acclimated and acclimated larvae after 7 days at ?5 °C, 10 days at 0 °C and 13 days at 5 °C. Field trials showed that neither non‐acclimated nor acclimated larvae survived longer than 1 month when exposed to naturally fluctuating winter temperatures. These results suggest that releasing E. eremicus into British greenhouses would pose minimal risk because typical British winter temperatures would be an effective barrier against establishment in the wild.     

Life cycle and abundance oflongitarsus jacobaeae [Col.: Chrysomelidae], biocontrol agent ofSenecio jacobaea

The life cycle and abundance of the tansy ragwort flea beetle,Longitarsus jacobaeae (Waterhouse), were investigated in a dune area in the Netherlands. The beetle overwinters in the egg stage, which is parasitised by a Mymarid wasp. No larvae were found until spring. Three larval instars can be separated by head capsule size and coloration. Initial larval numbers are high (up to 214 larvae per plant), but drop to very low levels by late spring. Adults appear during June or July, the numbers are high until October, the adults can be found until the end of December. This life cycle differs remarkably from those described for the species in Switzerland, Italy and Britain. Possible causes for these differences are discussed, as well as implications for the use ofLongitarsus in biological control.      

Prevalence of Infective Ova of Toxocara Species in Public Places

Out of a total of 800 soil samples from public places all over Britain ova of Toxocara species were found in 24·4%. Ova from 20 samples were incubated and active embryos developed in all; these were fed to eight mice and active larvae were later recovered from the livers of six. Some children living near these parks had become infected with toxocara. Clearly more control of pollution of public places by dogs and cats is needed.     

Studies on the epidemiology of Strongylus vulgaris infection of the horse.

Observations are reported on the size and age structure of Stronglyus vulgaris populations recovered from the anterior mesenteric artery and its main branches of horses slaughtered at regular intervals throughout a year. Marked seasonal variations were found in the mean monthly numbers of worms present. During spring/early summer the numbers were relatively low and a large proportion of the arteries had no worms in them at all. Thereafter, the arterial worm burdens quite rapidly increased and the highest levels were reached during the winter months. During summer, small, newly-arrived larvae were quite abundant but by the end of the year well-developed (fifth-stage and late fourth-stage) worms predominated. These observations support the view that S. vulgaris is in Britain an annual species completing its development mainly during the winter months of the year.     

GB Non-native Species Information Portal: documenting the arrival of non-native species in Britain

Information on non-native species (NNS) is often scattered among a multitude of sources, such as regional and national databases, peer-reviewed and grey literature, unpublished research projects, institutional datasets and with taxonomic experts. Here we report on the development of a database designed for the collation of information in Britain. The project involved working with volunteer experts to populate a database of NNS (hereafter called “the species register”). Each species occupies a row within the database with information on aspects of the species’ biology such as environment (marine, freshwater, terrestrial etc.), functional type (predator, parasite etc.), habitats occupied in the invaded range (using EUNIS classification), invasion pathways, establishment status in Britain and impacts. The information is delivered through the Great Britain Non-Native Species Information Portal hosted by the Non-Native Species Secretariat. By the end of 2011 there were 1958 established NNS in Britain. There has been a dramatic increase over time in the rate of NNS arriving in Britain and those becoming established. The majority of established NNS are higher plants (1,376 species). Insects are the next most numerous group (344 species) followed by non-insect invertebrates (158 species), vertebrates (50 species), algae (24 species) and lower plants (6 species). Inventories of NNS are seen as an essential tool in the management of biological invasions. The use of such lists is diverse and far-reaching. However, the increasing number of new arrivals highlights both the dynamic nature of invasions and the importance of updating NNS inventories.     

Population density and geographical range size in the introduced and native passerine faunas of New Zealand

The current avifauna of New Zealand comprises species with two distinct origins: those that evolved in New Zealand or colonized naturally from neighbouring landmasses, and those that were deliberately introduced to the islands by European settlers. Elsewhere, it has been shown that for species introduced to New Zealand from Britain there is a positive interspecific correlation between the geographical range sizes attained in both countries. Since positive relationships between abundance, measured either as population size or density, and geographical range size are a near ubiquitous feature of assemblages of closely related animal species, this suggests that species’ abundances may also be so correlated between the two countries. Here, data for 12 passerine bird species introduced to New Zealand from Britain are used to compare population densities and density–range size relationships in their native and alien ranges. In addition, the density–range size relationship for 12 passerine bird species that can be considered native to New Zealand is compared to that for the introduced species. The geographical range size and the mean and maximum densities of introduced species in New Zealand were significantly positively correlated with those values for the same species in Britain. However, in no case was the relationship between mean density and range size significant. While not statistically significant, density–range size relationships for introduced species are similar in New Zealand and Britain, but those for introduced and native species in New Zealand are quite different. Implications of these patterns are discussed.     

The effect of weather on the life cycle of the speckled wood butterfly Pararge aegeria

ABSTRACT.

• 1 Pararge aegeria (L.) is a very unusual butterfly of Britain, having a long period of adult activity, from April to October, without discrete flight periods. In central Britain it overwinters in two stages: pupae and third instar larvae, both being the progeny of late summer adults. Other larval stages die at the onset of cold winter weather. The overwintering stages give rise to the first adult generation in spring, split into two parts.
• 2 Different temperature regimes affect development rates in larvae and pupae differently. Late larval development is more rapid than that of pupae at low temperatures, thus in cool spring weather the overlap of the two parts of the first generation is greater than in warm spring weather.
• 3 Adults emerge continuously throughout the summer because larval development rates are variable. When summer is warm there is a partial third generation but when cool only two.
• 4 The timing of the end of the flight period is consistent with the hypothesis that both temperature and photoperiod are important in determining whether individuals enter diapause or develop directly. In warm summers larvae develop beyond a sensitive stage before critical daylength is reached and develop directly, but in cool summers individuals enter diapause because they are at the sensitive stage when critical daylength is reached.
• 5 It is suggested that variable development rates can facilitate parasite escape in autumn and increase the probability of adult success when weather is unpredictable, and this strategy is maintained because these benefits are greater than the cost of winter mortality of larvae.

     

Studies on the Lumbriculidae (Oligochaeta) in Britain

Seven species of Lumbriculidae, a family of fresh water Oligochaeta, found in Britain are described and a key is erected for their identification. Two species of Trichodrilus , separated by Beddard are redescribed, resulting in a new synonymy. Trichodrilus Hrabêi sp. n. from Denbighshire is denned. Dorydrilus michaeheni is recorded for the first time from Great Britain.     

The morphology of Giffordia hincksiae (Harv.) Hamel on the south coast of Britain

Giffordia hincksiae (Harv.) Hamel collected on the south coast of Britain shows considerable form range. General morphological and reproductive characters for the species are given. Four forms are described, and three types of sporangia, including the long unilocular sporangium not previously recorded on this species in Britain.     

Steinernema kraussei,an indigenous nematode found in coniferous forests: efficacy and field persistence against Hylobius abietis

1 More than 100 ha of forest restocking sites in Northern Britain are treated annually with the entomopathogenic nematode Steinernema carpocapsae to control larvae of the large pine weevil, Hylobius abietis. However, data on geographical distribution, thermal niche breadth and foraging strategy suggest that S. carpocapsae may be a poor choice for this application. 2 We undertook laboratory and field experiments that compared S. carpocapsae with Steinernema kraussei for efficacy towards H. abietis. Steinernema kraussei is indigenous to Northern Britain, active at low temperatures and is thought to adopt a ‘cruise’ foraging strategy particularly suitable for finding subterranean sedentary insects such as H. abietis. Conversely, S. carpocapsae has not been recorded in Northern Britain, prefers warmer temperatures and is thought to remain at the soil surface adopting an ambush foraging strategy. 3 There were no differences in the ability of the two nematodes to infect and kill larvae of H. abietis in laboratory experiments and, in two field experiments, both species were equally effective both in terms of parasitizing larvae within the stumps and reducing emergence of adult H. abietis. In one experiment, we monitored persistence of nematodes for 1 year after application and found S. kraussei persistence was much greater than that of S. carpocapsae. 4 The greater persistence of S. kraussei suggests that this nematode is better adapted to conditions in Northern Britain, but this may potentially represent a greater threat to nontarget insects. 5 Our data suggest that there would be little benefit associated with substituting S. kraussei for S. carpocapsae in integrated pest management systems for H. abietis.     

Lack of pre-dispersal seed predators in introduced Asteraceae in New Zealand

The idea that naturalised invading plants have fewer phytophagous insects associated with them in their new environment relative to their native range is often assumed, but quantitative data are few and mostly refer to pests on crop species. In this study, the incidence of seed-eating insect larvae in flowerheads of naturalised Asteraceae in New Zealand is compared with that in Britain where the species are native. Similar surveys were carried out in both countries by sampling 200 flowerheads of three populations of the same thirteen species. In the New Zealand populations only one seed-eating insect larva was found in 7800 flowerheads (0.013% infected flowerheads, all species combined) in contrast with the British populations which had 487 (6.24%) flowerheads infested. Possible reasons for the low colonization level of the introduced Asteraceae by native insects in New Zealand are 1) the relatively recent introduction of the plants (100-200 years), 2) their phylogenetic distance from the native flora, and 3) the specialised nature of the bud-infesting habit of the insects.     

Changes in the composition of British butterfly assemblages over two decades

Changes in the abundance and distribution of individual species have been widely documented in Britain and other countries in recent decades, but little has been done to determine changes in community composition over broad geographic areas. Here, we studied species turnover in 51 butterfly assemblages in Britain since 1976, examining extinction and colonisation events together with variation in the abundances of the species. We showed that the species turnover that occurred over 20 years in Britain was associated with colonisation and extinction events and also with variability in the abundance of the species. These changes in community composition differed according to the habitat requirements of the species and their previous distributions, being more evident for habitat specialists and for southerly distributed species. Colonising species often became abundant components of the communities they joined, although this was more evident for generalist than for specialist species. The abundance of species following their arrival, increased with time since colonisation. Species turnover associated with southerly species expanding northwards is consistent with being a response to climate change. The results suggest that climate- and habitat-driven changes in the identity and abundance of species within communities are widespread, and probably ubiquitous. Similar changes are likely to be occurring in other groups of organisms that are similarly undertaking major range shifts associated with climate change.     

The taxonomy and biology of two sympatric sibling species of Culex, C. pipiens and C. torrentium (Diptera, Culicidae)

The mosquito Culex torrentium Martini is a sibling species of C. pipiens L. and was first discovered in Britain in 1951. However, it is now evident that it was present in this country from at least 1900. Collections from a few southern localities in England indicate that the size of its population is about a third that of C. pipiens.
A comparative taxonomic study showed that neither the eggs nor larvae can be separated from those of C. pipiens , and that only in certain instances can the pupae of the two species be distinguished. Males are readily separated on the structure of the terminalia. Previously it was considered that C. torrentium could be distinguished by the presence of a pre-alar patch of scales, but it is shown that in a few specimens they are absent and in others they may become easily detached.
Larvae of both species frequently occur together in the same habitats, and no differences were observed in the biology of their immature stages. Serological tests showed that adults of both species feed on birds. Adult females of both species hibernate during the autumn, but whereas those of C. pipiens are common in man-made shelters, C. torrentium is absent.