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The effect of organic farming regimes on breeding and winter bird populations : part 4 = Invertebrate and weed seed food-sources for birds in organic and conventional farmin systems (1995)

David Brooks John Bater H Jones P. A. Shah

1.1 Introduction 1.1.1 Aim of project .To compare the abundance of invertebrate and weed seed food resources available to birds on orzanic and conventional farmland. The objective of the studv was to assess accurately the likely benefit of these farming systems to birds feeding on farrn'land, by sampling invertebrates and weed seeds. 1.1.2 Factors implicit to achieving the project aims Variation between farms within one system could influence' invertebrate or weed seed abundance and bias results, To minimise such effects and provide results 'representative of the farming systems as a whole, sampling was based on an extensive approach; farms were sampled in groups. The inference that either of the farming systems is beneficial to feeding birds is dependent on: (i) prior knowledge of the relevance of a particular invertebrate or seed as a food-source: evidence (ii) that this foodsource is present in sufficient abundance and (iii) that the food-source is readily accessible, The methodology described below was refined to address these criteria. 1.1.3 Methodology Sampling concentrated on cereal crops, with an additional comparison of organic grass ley fields at a limited number of sites. Sampling initially consisted of sucking invertebrates from the crop using a vacuum insect net and extraction from soil cores. To aid the interpretation of results from this sampling, it was decided that more information was required on the diet of birds. This was achieved by analysing faecal sacs for undigested fragments of invertebrates that therefore represented a dietary component. Skylark chick faecal sacs were chosen for analysis as this was the key species for the intensive ornithological studies and samples could be taken during routine fieldwork. As a result of this study, the main invertebrate sampling technique was changed to pitfall traps, since this was a superior method for assessing those invertebrates found to be important food-sources. It was also anticipated that pitfall trapping would provide more accurate estimates of invertebrate availability, with greater numbers per sample, than the previous two techniques. Studies of weed seed food resources consisted of field surveys using a quadrat to assess the presence and abundance of species, and the use of a small hand held suction machine to suck seeds from post-harvest stubble. The interpretation of the results emphasised the aspects of the ecology of species known to be food-sources that might influence their availability to birds. 1.2 Soil core and vacuum samples 1.2.1 Significantly more dipteran immature stages and Coleoptera were found in soil cores on organic grass ley fields and significantly more earthworms on organic cereal fields than conventional cereal fields. Earthworms and dipteran larvae such as tipulids are known to be important food-sources for birds that specialize in soil invertebrates. 1.2.2 Total numbers of invertebrates trapped by both methods did not differ significantly between the two farming systems. Significantly more invertebrates were trapped, however, by both methods on organic grass ley fields than either conventional or organic cereals. 1.2.3 Significantly more Staphylinidae tCol.), especially the species Tachyporus hypnorum, were found on conventional fields, The relevance of this species as a food-source is, however, doubtful. 1.2.4 The weevil Sitona lineatus and the carabid Demetrias atricapillus were found in significantly greater numbers on organic fields. The former may constitute a food-source for skylarks, which have been shown to feed on this insect under laboratory conditions. 1.3 Faecal sac analysis 1.3.1 Carabid beetles were an important component of skylark chick diet, forming 47 % of identifications. In some cases it was possible to identify the species present. 1.3.2 Coleoptera, other than carabids, from the families Elateridae, Curculionidae, Chrysomelidae and Staphylinidae were identified as food-sources. 1.3.3 Spiders and tipul ids were also important components. 1.3.4 Reservations are expressed that the technique may under-represent soft-bodied invertebrates, which are susceptible to complete digestion by skylark chicks. 1.4 Pitfall trap samples 1.4.1 Twelve key species of carabid beetles were analysed. of which five cornmon species were trapped in significantly greater numbers on organic farms. These were Pterostichus melanarius (the dominant species captured), Pterostichus madidus, Harpalus affinis, Harpalus rufipes and Nebria brevi collis. The other species analysed showed no significant variance between farming systems. 1.4.2 Williams' Index of Diversity was significantly greater for conventional fields, although caution is expressed over the reliability of this result due to the small sample size of species. 1.5 Botanical studies 1.5.1 The abundance of weed plants in quadrats was significantly greater on organic fields. 1.5.2 The abundance of weed seeds was not significantly different between farming systems. However, the relative proportions of monocotyledonous and dicotyledonous seeds in samples differed between farming systems. A larger proportion of the seeds from organic fields were dicotyledonous and from conventional fields were monocotyledonous. 1.5.3 Preliminary examination of the size of plants and the number of seeds produced suggested that those on organic fields may have been nitrogen deficient. 1.5.4 Weed species were significantly more diverse on organic fields. although diversity has less relevance to bird feeding than abundance. 1.6 Proposals for future work 1.6.1 Replication of the pitfall trapping exercise in subsequent years would substantiate the trends established from the data of one season. It would also be beneficial 10 extend the range (If habitats sampled to take into account set-aside and other crops besides cereals. 1.6.2 More comprehensive information. on the diet of farmland birds in general. could he achieved by analysing the faecal sacs of a wider variety of species. 1.6.3 Greater integration of field studies on birds with invertebrate sampling would enhance the effectiveness of the latter as an indicator of diet. Areas of farmland frequently selected as feeding sites by birds could be sampled intensively for invertebrates and compared to other areas, selected at random. This would provide useful information on the invertebrates likely to be important as food-sources and the habitats that favour them. 1.6.4 Extending the range of farms sampled would provide more accurate results. 1.6.5 More work is required to-investigate the possible link between nitrogen deficiency in plams and organic systems, and its implications for the provision of bird food-sources, particularly for weed abundance and phytophagous insects.

The prosobranch molluscs of Britain and Denmark : Part 8 - Neogastropoda (1985)

Vera Fretter Alastair Graham

Neogastropods are usualiy accepted as the most advanccd prosobranchs, though their organization is approached in several respects in some higher families of Mesogastropoda. This seems, however, to be due to parallel evolution and the neogastropods originated from a much lower grade of mesogastropod. Although some workers derive them from an archaeogastropod stock there are too many features in their anatomy characteristic of mesogastropods rather than of archaeogastropods for this to bc acceptable. On the whofe, neogastropods are a rather uniform group of prosobranchs in their shell, external features, and internal anatomy. In only one System do they show, by comprison with archaeo- and mesogastropods, both extreme specialization and considerable variation: this is the gut, which is in several ways unlike that of any other prosobranch. This is to be associated with their carnivorous way of life, in which respect they again differ markedly from meso- and archaeogastropods. Taylor, Morris Br Taylor (1980) have shown how neogastropod species differ amongst themselves not, primarily, in their rnode of life, but in their often narrow choice of prey. Since the anatomical requirements for predation are more or less constant, the different species remain similar in organization and are often sympatric. In these respects neogastropods differ markedly from mesogastropods, whose adaptive radiation has been extensive and primarily in relation to mode of life. Separation of neogastropods from mesogastropods rests mainly on the siphonal canal in the shell, the siphon on the mantle edge, the rachiglossate or toxoglossate radula, and the presence of a pleurembolic proboscis or one of its varieties (Smith, 1967). The osphradium is large and its axis carries a double series of lamellae, giving it a gill-like appearance. Males always have a penis and females usually a ventral pedal gland. lnternally the anterior part of the alimentary caiial has becorne elaborate, with a complex glandular equipment, and the wall of the kidney is more folded than in mesogastropods. The nervous systern is concentrated, though the visceral ganglia remain posteriorly placed. Eggs are laid in capsules attached to the substratum. A free larval stage is often suppressed and food eggs are common, but neither of these features has much taxonomic significance, occurring apparently randomly throughout the group. Because of their general similarity classification of the Neogastropoda has proved to be no easy task, and there is still no universally-accepted subdivision of the order into superfamilies. It is generally agreed, however, that the order may be split into two groups, primarily on the basis of radular structure. The more primitive of these, the Rachiglossa, has a radula with typically 3 teeth per row; the more advanced, the Toxoglossa, has a radula which, in more primitive genera, resembles the rachiglossate, but which Comes, in more advanced toxoglossans, to have only a single tooth in action at a time. Each tooth has then become scroll-like and is used for the injection of poison from a poison gland into the prey (Shimek & Kohn, 1981). The group Toxoglossa is agreed to contain the superfamily Conacea which includes (as Recent forms) the families Turridae, Conidae, and Terebridae, all with poison apparatus, though with very different shells. Risbec (1955), followed by Taylor & Sohl (1962), has added a second superfamily Mitracea containing, in the family Mitridae, a grouping of genera selected from that family as earlier understood. These have a rachiglossate radula and an apparent poison gland not irnrnediately comparable with that of undoubted toxoglossans. This reclassification of mitrids has not found favour with subsequent workers (Cernohorsky, 1966, 1970; Ponder, 1972). Ponder (1973) made a case for adding a third suborder to the two mentioncd above. This was to contain the single superfamily Cancellariacea with the one family Cancellariidae. The case rests on the unique character of their radula. It is, however, when one turns to the remaining rachiglossan families and- attempts to assign them to superfamilies that difficulties mount. Three groupings Iiave been conventionally recognized - Muricacea, Buccinacea, and Volutacea, though it has often appeared that the last was a collection of animals not obviously assignable to the other two rather than clearly related amongst thernselves. Ponder (1973) came to the somewhat pessimistic conclusion that all rachiglossans should be put into a single taxon, for which he used the name Muricacea. It seems to us, however, that certainly within the limited group of anirnals with which we have to deal here, but even in a broader context, there is still some validity - and certainly convenience - in the older Separation, when due importance is given to internal anatomy; we propose, therefore, to retain the three superfamilies in dealing with a group which is otherwise too large for easy treatment. We adopt this arrangement the more readily as we have no volutacean mernbers of the fauna with which we have to deal, provided that we accept Ponder's proposal to create a separate superfamily for cancellariids. This allows the remaining superfamilies to be split into Muricacea and Buccinacea, and it is between these two superfamilies that lines of division may most obviously be drawn. Taylor & Sohl (1962) noted about 800 genera and subgenera in the rachiglossan group. The Buccinacea, with nearly 400, is rivalled for size only by the superfamilies Rissoacea and Cerithiacea amongst all the prosobranchs. A difficulty arises at this point in relation to the number of species which have been described. Many neogastropods are not intertidal in occurrence. Their capture is dependent upon dredging, a method which can often do no more than sample a few isolated spots on the ocean bed. Many species have been described on the basis of these samples without any real knowledge of the variation whjch may affect populations. It seems, indeed, probable that many of these are no more than local varieties, especially when it is remembered that the anatomy of many is very imperfectly known. We have, therefore, been conservative in nomenclature and tended to use broad generic groupings where others might have used narrower ones. The latter may be right, but it is prernature to be sure of this.

The prosobranch molluscs of Britain and Denmark : Part 9 - Pyramidellacea (1986)

Vera Fretter Alastair Graham Elizabeth B Andrew

A comparative study of the symbiotic relationship between beetles of the genus Cremastocheilus (Coleoptera: Scarabaeidae) and their host ants (Hymenoptera: Formicidae) (1994)

Gary Duane Alpert

The North Arnerican species of the genus Cremastocheilus are reviewed. These belong to 5 subgenera, Macropodina, Trinodea, Anatinodia, Mymcotonus, and Cremastocheilus. Taxonomie changes are: She inclusion of Crernastocheilus nitens and C. chapini in the subgenus Cremastocheilus rather than Myrmecotonus. Also Anatinodia is elevated to subgeneric status. A key to the subgenera is provided, as is a key to the species of the 5 subgenera, recognizing that the 35 species in the subgenus Cremastocheilus are in need of revision. A critical review of the host records, geographic distribution, and ecology of the Tribe Crernastocheilini (Family Scarabaeidae. subfamily Cetoniinae) is provided. This contains enormous numbers of new records for both the genera Genuchinus and CremastocheiLus both from the literature and from the extensive field work that is reported here for the first time. A Summary of the host records is presented in tabular form. This table shows the association of all species of Cremastocheilus with ants as adults and the larvae either associated with the vegetable material of the ant nests or with vegetable material in rodent burrows. Genuchinus is shown to be a general predator on soft bodied insects while the other genera of the Cremastocheilini are associated with plants, particularly bromeliads. A detailed study of the external morphology and sexual dimorphism of the genera Genuchinus and Crernastocheilus is presented. All species of Cremastocheilus can be sexed with the naked eye by the difference in the shapes of the abdominal terminal Segments, wherein males have the posterior border of the last ventral abdominal segment either straight or slightly bowed, while females have this border broadly rounded. There are other microscopic sexual differences in the structure of the legs. The rest of the external morphology is also presented, particularly from the point of view of adaptations to either a predaceous or rnyrmecophilous existente. Particularly adapted for predation are the pointed maxillae which are used for piercing prey. Particularly adapted for myrmecophily are the mentum, the maxillae, the generally thick exoskeleton, trichomes on both the anterior and posterior angles of the pronotum, the elytra, and the legs (which are adapted to the nest substrate of the host ant nests. Exocrine glands are described for Genuchinus ineptus and at least 1 species of each of the 5 subgenera of Cremastocheilus. In general, there are no gland cells nor glandular areas in Genuchinuc that are comparable to those of Cremastocheilus. The gland cells and glandular areas are quite extensive andvariable arnong species of Cremastocheilus. The frontal gland of some Cremastocheilus (strongly developed in C. castaneus and the C. canaliculatus species group, but weakly developed in the C. wheeleri species group) is described for the first time. Because these glands are not found in Genuchinus ineptuc, a species with general predatory habits, it is thought that these play a role, as yet unknown, in interactions with ants. The life cycles of the subgenera of Cremastocheilus are described. The general life cycle entails adult beetles eclosing in ant nests during the summer and then undertaking dispersal flights. The adults then enter ant nests and ovenivinter there, eating ant larvae during the Winter. Another dispersal flight occurs in the spring during which the adults mate and enter ant nests again. The females then lay eggs and the adults die. The eggs hatch and the larvae spend 3 instars feeding upon vegetable material in the nests. The lmae then pupate in typical scarabaeine earthen cells made of fecal material and soil. These eclose in the summer and the cycle is repeated. Variation from species to species is largely in the timing. Leaving the nest in late Summer, mating seems to be triggered by rainfall in all the species studied. Mating of C. (Macropodina) beameri takes place in rodent burrows. Males seem attracted to females from a distance but the mechanism of this remains obscure. In the subgenus Trinodia, mating takes place on sandy washes or roadsides where females land. In the subgenus Myrmecotonus, maüng also takes place in sandy areas. In C. (Cremastocheilus) mating takes place on sand bars along rivers in the southeastern U.S. and in sand dunes in northeastern U.S. The femaies dig down into the sand. Males locate these places by some unknown mechanism and then dig down to copulate with the females. Field experiments showed unequivocaily that males dig only into areas occupied by females. No sex-specific Sex attractant glands have been located in females so far. Dispersal to ant nests occurs after mating except for C. (Macropodina) beameri which lays its eggs in the rodent burrows and then probably disperses to ant nests. Beetle activity going in and out of nests was studied using wire hardware cloth screens over entrances to Mynnecocystus nests. The mesh size was such that the ants could move freely in or out but the beetles got stuck by their thoraces. The direction then could be interpreted by the direction in which they got stuck. By this method, C. stathamae was shown to leave nests from 23 June to 1 September with a peak on 6 July, just after the beginning of the summer rains. Beetles entered nests from June 23 to August 3, however 39% entered on July 16, probably pulsed by the leaving time which was correlated with the rains. Life cycle timing: C. (Macropodina) develop in the nests of Wood rats (Neotoma sp.]. Females lay about 40 eggs each. The 3 larval instars to pupation take about 1 month. Pupae are found from late August to weil into September. In other subgenera as well, larvae are found in parts of the nest devoid of ants, The timing is similar in all the subgenera found with ants. Mortality factors: While ants attack Cremastocheilus adults, there is no evidence that they are ever killed by ants nor is there evidence that ants kill larvae nor hard earthen pupae cases which protect the pupae. During dispersal fiights and mating, the adults are exposed to predation and evidence is presented that shows predation by horned toads, spiders, magpies, and tiger beetles. Probably most mortality occurs in the larval and pupd stages where the beetles are attacked by internal parasites and fungus. Further rnortality is caused by limitation of the food supply during the larval stage. Reentering nests: Females of C. (Macropodina) beameri select specific rodent and other burrows, attract males for rnating. and then enter the burrow for oviposition. C. stathamae are carried into the ants nests from as far away as 25ft. The beetles appear to land spontaneously after flying randomly over M. depilis nesting areas. Then the wander about waiting for the ants to carry them into the nests. Cremastocheilus hirsutus fly low over the ground searching for Pogonomyrrnex barbatus nests, land. and move straight for the nest entrances which they enter unhindered. Among all species, the ants frequently eject beetles but the net rnovement is in. Ants frequently attacked Cremastocheilus in laboratory observation nests when they were introduced. These attacks seldom resulted in the death of the beetles and the beetles were eventually ignored. When the beetles entered brood chambers, where they fed upon larvae, they were mostly ignored and even licked assiduously by the ants. A principle defensive behavior by the beetles is feigning death (letisimulation). The beetles give off an unpleasant "dead fish odor when collected in the I field. Experiments show that this substance functions to fend off some predators but further experiments indicated that these substances were ineffective against both ants and kangaroo rats. Experiments with various species of Cremastocheilus adults indicate that the adults eat only ant larvae. The beetles will eat larvae of non-host ants but show preferences for the larvae of their normal hosts. Under the same experimental conditions. Genuchinus ineptus adults will feed on a variety of insect adults and larvae. Field experiments on the function of trichome secretions did not indicate that they function to attract ants at a distance nor are they involved in worker acceptance. Laboratory experiments in which areas with a high concentration of gland cells were presented to ants showed that no ants were attracted. Laboratory introduction of Cremastocheilus hamisii adults into Fomica schau.si nests yielded many interactions including ants licking the anterior pronotal angles, the mentum area where the frontal glands empty and a carina over the eye with a dense pad of short setae. These are areas of concentration of gland cells and these are the first observations of licking by ants in specific sites containing exocrine glands. Radioisotope experiments showed food exchange among ants but never from ants to beetles. Other experiments showed that ants can pick up radioactivity from the beetles without feeding on trichome secretions. Evolutionary pathways: Adult Cremastocheilini probably followed the evolutionary route from adult predation on soft bodied insects to specialized feeding upon ant brood and the subsequent development of the beetle larvae in vegetable material in the ant colonies. Thus Genuchininseptus makes a logical outgroup in that they are general predators probably feeding mostly on Diptera larvae associated with Sotol plants in the field. The rnajor evolutionary step taken by Cremastocheiluswas to specialize on ant brood. Then the species radiated into ant colonies inhabiting southwestem North Arnenca. Most of the ant hosts invaded have quantities of vegetable material in their nests sufficient to support several developing scarab larvae. Host colonies are large, contain accessible brood, and are usually dominant foragers Evidence supports the idea that the species of Cremastocheilus have differentes in behavior and morphology that reflect adaptation to the behavioral ecology of different species of ants rather than different evolutionary levels of integration into ant colonies.

Survey of phytoseiid mites (Acari: Phytoseiidae) in orchards and surrounding vegetation of northwestern Europe, especially in the Netherlands : keys, descriptions and figures (1987)

E. Miedema

Nine genera of phytoseiid mites with 22 species are described and illustrated on the basis of a survey of the literature, and by examination of material from orchards and their surroundings and of material from museum collections. Males, if available, are also described and figured. In addition to the species listed for the Netherlands, six species from around orchards in East Germany, Belgium and Poland were described briefly, and related species from other European countries (especially the British Isles and Germany) are noted. For each genus, a key to species (adult females) is given. For each species, a diagnosis is presented, and taxonomic problems are discussed for the following taxa: PhYloseius macropilis (Banks); Amblyseius reduclus Wainstein; A. cucumeris (Oudemans); A. masseei (Nesbitt); A. pOlentillae (Garman); A. rademacheri Dosse; A. isuki Chant. Keys are based on easily recognizable features and are aimed at "the interested non-taxonomist".

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