Components of resistance to the sorghum midge, Contarinia sorghicola

Studies were conducted on components of resistance to sorghum midge on four resistant (DJ 6514, AF 28, TAM 2566 and IS 15107) and two susceptible cultivars (CSH 1 and Swarna). Data were recorded on the numbers of eggs, larvae, emerged adults and grain damage in panicles of different genotypes infested with 60 midge females/panicle under no-choice conditions. The size of floral parts (glume, lemma, palea, lodicule, stigma, style, ovary and anther), rate of grain development and tannin content of grain were measured. The lengths of glume gl and 82, lemma L1 and L2, palea, lodicule, anther, style and stigma were positively associated with susceptibility to sorghum midge. Rate of grain development (between 3rd and 7th day after anthesis) was negatively associated with susceptibility to sorghum. Tannin content of grain was also negatively correlated with midge susceptibility, although there were distinct exceptions (e.g. DJ 6514 is highly resistant bur has a low tannin content).     

Floral biology and pollination strategy of seven Tacca species (Taccaceae)

We investigated the floral characteristics, floral biology and floral visitors of the six Bornean Tacca species: T. bibracteata (only floral characteristics), T. borneensis, T. havilandii, T. leontopetaloides, T. palmata and T. reducta, and T. cristata from Peninsular Malaysia. All species are protogynous with pollen strings extruded post flower opening. Blooming of all species started from dawn except for T. leontopetaloides which flowered from dusk. While T. borneensis, T. cristata, T. havilandii, T. leontopetaloides and T. reducta are facultatively autogamic as the pollen/ovule ratios (P/O ratios) were low, T. bibracteata is facultatively xenogamic as its P/O ratio was higher. Four species (T. borneensis, T. cristata, T. havilandii and T. reducta) were tested for autonomous self-pollination but all failed to set fruit. Manual self- and cross-pollination treatments of T. borneensis, T. cristata and T. havilandii showed reduced fruit set and seed set. In contrast, T. reducta was highly self-compatible. The showy bracts and bracteoles of T. borneensis are needed to guarantee pollination success but is not so in the other species investigated. Tacca are pollinated by two pollination guilds of female midges: two species of Forcipomyia (Lasiohelea) and Culicoides hinnoi. The floral biology and mating system of Tacca species indicate that most fruits and seeds were produced in samples resulting from natural pollination.     

A review of the biology,ecology and control of saddle gall midge,Haplodiplosis marginata (Diptera: Cecidomyiidae) with a focus on phenological forecasting

Saddle gall midge Haplodiplosis marginata (Diptera: Cecidomyiidae) is a pest of cereals across Europe. The occasional nature of this pest has resulted in limited and sporadic research activity. There remain important gaps in knowledge due either to a genuine lack of research or to previous research being difficult to access. These knowledge gaps make the development of effective control options difficult. Here, we review the existing literature in an attempt to consolidate the information on H. marginata from research which spans several decades and encompasses many different countries. The current distribution and pest status of this insect are updated, along with the methods of cultural and chemical control available to growers. The biology and life history of the insect are described in detail and the ecological processes governing them are discussed. A forecasting model is presented which allows the emergence of this pest in the UK to be predicted from degree day data, and the potential application of this model in management decisions is discussed. Finally, the areas in most need of further research are identified, along with suggestions of how this information can be used to help develop effective and sustainable management solutions for this pest.     

CHANGES OF FATTY ACIDS IN LARVAE OF THE WHEAT BLOSSOM MIDGE,SITODIPLOSIS MOSELLANA (GEHIN) (DIPTERA: CECIDOMYIIDAE)*

Abstract The changes of fatty acids in larvae of the wheat blossom midge, Sitodiplosis mosellana (Gehin) at different periods were examined by gas choromatography. There were 10–16 kinds of fatty acids, of which the predominant ingredients were palmitic (C_16:0), oleic (C_18:1) and linoleic (C_18:2) acids which were more than 95% in total fatty acids, stearic acid (C_18:0) about 2%‐3.5% and any of the others was less than 1%. The fatty acid compositions increased from mid‐May, when larvae of the wheat blossom midge left the wheat‐ears and fallen on the ground, to April of next year before pupating and emerging. No arachidic acid (C_20.0) was discovered in over‐summering, over‐wintering as well as inactive over‐wintered larvae. The content of saturated fatty acids in over‐summering, overwintering as well as inactive over‐wintered larvae were less than those of in active over‐wintered larvae and wheat‐ear larvae. Therefore, changes of the arachidic acid and the proportions of saturated fatty acids/unsaturated fatty acids could be used as one of the biochemical criteria to determine the active state and the degree of diapause in larvae of the wheat blossom midge.     

The intramandibular joint in Girella: A mechanism for increased force production?

Intramandibular joints (IMJ) are novel articulations between bony elements of the lower jaw that have evolved independently in multiple fish lineages and are typically associated with biting herbivory. This novel joint is hypothesized to function by augmenting oral jaw expansion during mouth opening, which would increase contact between the tooth‐bearing area of the jaws and algal substratum during feeding, resulting in more effective food removal from the substrate. Currently, it is not understood if increased flexibility in a double‐jointed mandible also results in increased force generation during herbivorous biting and/or scraping. Therefore, we selected the herbivore Girella laevifrons for a mechanical study of the IMJ lower jaw lever system. For comparative purposes, we selected Graus nigra, a non–IMJ‐bearing species, from a putative sister genus. Shortening of the lower jaw, during flexion at the IMJ, resulted in a more strongly force‐amplifying closing lever system in the lower jaw, even in the absence of notable changes to the sizes of the muscles that power the lever system. To explain how the IMJ itself functions, we use a four‐bar linkage that models the transmission of force and velocity to and through the lower jaw via the IMJ. When combined, the functionally interrelated lever and linkage models predict velocity to be amplified during jaw opening, whereas jaw closing is highly force modified by the presence of the IMJ. Moreover, the function of the IMJ late during jaw closure provides enough velocity to detach sturdy and resilient prey. Thus, this novel jaw system can alternate between amplifying the force or the velocity exerted onto the substrate where food items are attached. This unique mechanical configuration supports the argument that IMJs are functional innovations that have evolved to meet novel mechanical challenges and constraints placed on the feeding apparatus by attached and sturdy food sources. J. Morphol. 2010. © 2009 Wiley‐Liss, Inc.     

Description of Eucalyptodiplosis chionochloae sp. nov., a cecidomyiid feeding on inflorescences of Chionochloa (Poaceae) in New Zealand

Abstract

A cecidomyiid that feeds on developing seeds in the inflorescences of the New Zealand tussock grasses Chionochloa australis, C. conspicua, C. crassiuscula, C.flavescens, C. macra, C. oreophila, C. pallens, C. rigida, C. rubra, C. spiralis and C. teretifolia is formally described from C. pallens. The new species, named Eucalyptodiplosis chionochloae Kolesik, is the most ubiquitous of flower feeders of Chionochloa. Its larvae do not form galls but feed on the developing seeds in autumn, overwinter as diapausing larvae inside the floret, and pupate then rapidly eclose in summer, sometimes after extended diapause. Methods for rearing adults are described. Based on its morphological characters this species is most closely related to two described congeners that form galls on buds of Eucalyptus trees in Australia. Seed predation by Eucalyptodiplosis chionochloae larvae appears to be the primary driver of the extreme mast seeding (variation among years in flower crops) seen in the host Chionochloa species.     

Effect of soil burial depth and wetting on mortality of diapausing larvae and patterns of post-diapause adult emergence of sorghum midge, Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae)

Abstract  In south-eastern Queensland, Australia, sorghum planted in early spring usually escapes sorghum midge, Stenodiplosis sorghicola , attack. Experiments were conducted to better understand the role of winter diapause in the population dynamics of this pest. Emergence patterns of adult midge from diapausing larvae on the soil surface and at various depths were investigated during spring to autumn of 1987/88–1989/90. From 1987/88 to 1989/90, 89%, 65% and 98% of adult emergence, respectively, occurred during November and December. Adult emergence from larvae diapausing on the soil surface was severely reduced due to high mortality attributed to surface soil temperatures in excess of 40°C, with much of this mortality occurring between mid-September and mid-October. Emergence of adults from the soil surface was considerably delayed in the 1988/89 season compared with larvae buried at 5 or 10 cm which had similar emergence patterns for all three seasons. In 1989/90, when a 1-cm-deep treatment was included, there was a 392% increase in adult emergence from this treatment compared with deeper treatments. Some diapausing larvae on the surface did not emerge at the end of summer in only 1 year (1989/90), when 28.0% of the larvae on the surface remained in diapause, whereas only 0.8% of the buried larvae remained in diapause. We conclude that the pattern of emergence explains why spring plantings of sorghum in south-eastern Queensland usually escape sorghum midge attack.     

Honey bee colonies from different races show variation in defenses against the varroa mite in a ‘common garden’

Honey bee [Apis mellifera L. (Hymenoptera: Apidae)] genetic diversity may be the key to responding to novel health challenges faced by this important pollinator. In this study, we first compared colonies of four honey bee races, A. m. anatoliaca, A. m. carnica, A. m. caucasica, and A. m. syriaca from Turkey, with respect to honey storage, bee population size, and defenses against varroa. The mite Varroa destructor Anderson & Trueman (Acari: Varroidae) is an important pest of honey bee colonies. There are genetic correlates with two main defenses of bees against this parasite: hygienic behavior, or removing infested brood, and grooming, which involves shaking and swiping off mites and biting them. In the second part of this study, we examined the relationship of these two types of defenses, hygiene and grooming, and their correlation with infestation rates in 32 genetically diverse colonies in a ‘common garden’ apiary. Mite biting was found to be negatively correlated with mite infestation levels.     

Early biting rhythm in the Afro-tropical vector of malaria, Anopheles arabiensis, and challenges for its control in Ethiopia

The biting cycle of the malaria vector Anopheles arabiensis Patton (Diptera: Culicidae) was assessed by hourly light trap collections in three villages in Tigray, northern Ethiopia. Hourly catches were conducted in two houses in each village, for four consecutive nights. Light traps were set from 18.00 hours to 07.00 hours in houses in which people slept under untreated bednets. Anopheles arabiensis showed early biting activities, which peaked between 19.00 hours and 20.00 hours in the three villages; over 70% of biting activity occurred before 22.00 hours, when people typically retire to bed. This early biting activity may have a negative impact on the efficiency of bednets to control malaria.