Entomology

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    The Genera Hemiberlesia and Abgrallaspis in North America with Emphasis on Host Relationships in the H. Howard (Cockerell) Complex (Homoptera: Coccoidea: Diaspididae)
    (1960) Davidson, John Angus Sr.; Bickley, William E.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
    The work reported consists of revisionary studies of Hemiberlesia Cockerell 1897 and Abgrallaspis Balachowsky 1948 in North America. The interpretation of North America is that of Ferris (1937), "all the mainland from the Arctic regions to and including the Panama Canal Zone." According to Ferris (1942), Hemiberlesia contained 15 species. As a result of this study, only eight of these species are here referred to Hemiberlesia. They are: rapax (Comstock), lataniae (Signoret), popularum (Marlatt), ignobilis Ferris, cupressi (Cockerell), diffinis (Newstead), candidula (Cockerell), and palmae (Cockerell). The species H. coniferarum (Cockerell) is newly assigned having previously been placed in Diaspidiotus Berlese and Leonardi, by Ferris. A tenth species, H. pseudorapax McKenzie, was assigned to this genus by its author. Seven of the 15 species have been assigned to Abgrallaspis. Both these genera appear to be North American in origin. Abgrallaspis was originally created for six species. Three of these occur in North America and were transferred from Hemiberlesia by Balachowsky. They are: palmae (Cockerell), degeneratus (Leonardi), and cyanophylli (Signoret). The last named species was designated as the genotype. Balachowsky (1953) later reassigned palmae to Hemiberlesia and transferred four more North American Hemiberlesia species to Abgrallaspis, namely, howardi (Cockerell), comstocki (Johnson), coloratus (Cockerell), and fraxini (McKenzie). A study of these species in the National Coccoid Collection revealed a complex centering about A. howardi as conceived by Ferris (1938). Usual morphological comparisons of slide mounted adult females failed to yield results, therefore, host transfer experiments were undertaken. A population of "howardi" of Ferris was secured on pachysandra. A total of 2,700 individual crawler transfers were then made to 20 different host plants. These hosts had been chosen because a preliminary study indicated unusual character variation in specimens collected from them. Fourteen of the test hosts (largely ornamentals) were later found to be infested with 14 to 54 per cent of the transferred crawlers. These crawlers were allowed to mature. Adult females were then collected and mounted for study. Six host plant species were completely unacceptable to infestation by the transferred crawlers. Five of these were plum, pear, peach, apple, and pine. A. howardi was described from plum in Colorado, and later recorded from such hosts as pear, peach, and apple. A study of the species Ferris synonymized with A. howardi revealed the test population to be A. townsendi (Cockerell), which was described from an unknown host in Mexico, and later recorded from a long list of ornamentals primarily in the southern and eastern United States. This species is redescribed and the name revalidated. A table is presented showing the variations found in salient taxonomic characters of A. townsendi collected from 14 different experimental host plants. Important variations in the size of the second lobes of A. townsendi were recorded. Second lobe reduction from three-fourths the length of the median lobes to mere hyaline points was observed. Specimens in the last category strongly resemble Diaspidiotus ancylus (Putnam). Aside from these second lobe variations, A. townsendi is a relatively stable species from the standpoint of host determined morphological variables. Avocado was the sixth test host on which transferred crawlers would not develop. Long series of scales from this host are present in the National Collection. They were collected from avocado fruit in quarantine at Texas, from Mexico. This species, A. perseus Davidson, is described as new herein. As here understood for North America, Abgrallaspis contains 13 species. Six were placed in this genus by Balachowsky, and seven by the writer. The last are: flabellata (Ferris) from Hemiberlesia; quercicola (Ferris) from Hemiberlesia; mendax (McKenzie) from Hemiberlesia; oxycoccus (Woglum) from Aspidaspis Ferris; ithacae (Ferris) from Aspidaspis; perseus Davidson as a new species; and townsendi (Cockerell) as a revalidated name. A brief presentation of materials and methods utilized in the host transfer experiments is followed by a discussion of the structural characters used in this work. Descriptions of Hemiberlesia and Abgrallaspis are accompanied by keys and descriptions to all the species in North America. Figures of adult female pygidial characters and scale coverings are provided for all species considered in these two genera.
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    The Bee Louse, Braula coeca Nitzsch, its Distribution and Biology on Honey Bees
    (1978) Smith, Irving Barton Jr.; Caron, Dewey M.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    Bee lice were found in 28% of Maryland apiaries and 18% of the colonies examined. In apiaries with lice, 50% of the colonies contained lice. Laboratory tests demonstrated that bee lice had no preference between 1, 5, 15, and 30 day old honey bee (Apis mellifera L.) workers at 25° while there was a preference for 1 day old workers at 34° C. Lice preferred young drones over old drones and virgin and mated queens over young drones at 25 and 34° C. Lice preferred virgin queens over old drones at 25° C while no preference was observed at 24° C. Mated queens were preferred over old drones at 25 and 34° C. There was a preference of lice for foraging age workers over old drones at 25° C while there was no preference at 34° C. Lice preferred both virgin and mated queens over random age workers at 25 and 34° C. Louse larval tunnels were numerous in nucs (4 frame honey bee colonies) stocked with lice from May through August corresponding with periods of nectar flow when bees were capping honey. In field colonies, louse populations decreased in the late spring to a low in early June. During July and after, populations of lice rose with the emergence of new lice. Few immature and adult lice were observed in control nucs having similar populations of bees. In nucs, 1 or more lice were observed on 24% of the queens between August and December. Only 2% of the virgin queens contained lice during the same period. In field colonies, 62% of the queens examined from June through the rest of the season harbored lice; 58% of these lice were pale in color indicating they were less than 1 day old. One louse was observed on 98.6% of the workers with lice, while 1.2% harbored 2 lice and 0.2% had 3 lice; 4 .2% of the lice were on drones. A single bee louse was observed on 3,092 foraging honey bees sampled. One-hundred-seventeen lice were collected on 14,459 bees collected from the brood nest of the same hives. Control samples indicated a 14 to 15% loss of lice during sampling. Tests demonstrated that during visual observations of lice on bees only 49% of the lice present were observed. Fluctuation in louse population levels were similar to those found elsewhere in this study.
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    Evidence for divergent selection between the molecular forms of Anopheles gambiae: role of predation
    (Springer Nature, 2008-01-11) Diabaté, Abdoulaye; Dabiré, Roch K; Heidenberger, Kyle; Crawford, Jacob; Lamp, William O; Culler, Lauren E; Lehmann, Tovi
    The molecular forms of Anopheles gambiae are undergoing speciation. They are characterized by a strong assortative mating and they display partial habitat segregation. The M form is mostly found in flooded/irrigated areas whereas the S form dominates in the surrounding areas, but the ecological factors that shape this habitat segregation are not known. Resource competition has been demonstrated between species undergoing divergent selection, but resource competition is not the only factor that can lead to divergence. In a field experiment using transplantation of first instar larvae, we evaluated the role of larval predators in mediating habitat segregation between the forms. We found a significant difference in the ability of the molecular forms to exploit the different larval sites conditioned on the presence of predators. In absence of predation, the molecular forms outcompeted each other in their respective natural habitats however, the developmental success of the M form was significantly higher than that of the S form in both habitats under predator pressure. Our results provide the first empirical evidence for specific adaptive differences between the molecular forms and stress the role of larval predation as one of the mechanisms contributing to their divergence.
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    Toward reconstructing the evolution of advanced moths and butterflies (Lepidoptera: Ditrysia): an initial molecular study
    (Springer Nature, 2009-12-02) Regier, Jerome C; Zwick, Andreas; Cummings, Michael P; Kawahara, Akito Y; Cho, Soowon; Weller, Susan; Roe, Amanda; Baixeras, Joaquin; Brown, John W; Parr, Cynthia; Davis, Donald R; Epstein, Marc; Hallwachs, Winifred; Hausmann, Axel; Janzen, Daniel H; Kitching, Ian J; Solis, M Alma; Yen, Shen-Horn; Bazinet, Adam L; Mitter, Charles
    In the mega-diverse insect order Lepidoptera (butterflies and moths; 165,000 described species), deeper relationships are little understood within the clade Ditrysia, to which 98% of the species belong. To begin addressing this problem, we tested the ability of five protein-coding nuclear genes (6.7 kb total), and character subsets therein, to resolve relationships among 123 species representing 27 (of 33) superfamilies and 55 (of 100) families of Ditrysia under maximum likelihood analysis. Our trees show broad concordance with previous morphological hypotheses of ditrysian phylogeny, although most relationships among superfamilies are weakly supported. There are also notable surprises, such as a consistently closer relationship of Pyraloidea than of butterflies to most Macrolepidoptera. Monophyly is significantly rejected by one or more character sets for the putative clades Macrolepidoptera as currently defined (P < 0.05) and Macrolepidoptera excluding Noctuoidea and Bombycoidea sensu lato (P ≤ 0.005), and nearly so for the superfamily Drepanoidea as currently defined (P < 0.08). Superfamilies are typically recovered or nearly so, but usually without strong support. Relationships within superfamilies and families, however, are often robustly resolved. We provide some of the first strong molecular evidence on deeper splits within Pyraloidea, Tortricoidea, Geometroidea, Noctuoidea and others. Separate analyses of mostly synonymous versus non-synonymous character sets revealed notable differences (though not strong conflict), including a marked influence of compositional heterogeneity on apparent signal in the third codon position (nt3). As available model partitioning methods cannot correct for this variation, we assessed overall phylogeny resolution through separate examination of trees from each character set. Exploration of "tree space" with GARLI, using grid computing, showed that hundreds of searches are typically needed to find the best-feasible phylogeny estimate for these data. Our results (a) corroborate the broad outlines of the current working phylogenetic hypothesis for Ditrysia, (b) demonstrate that some prominent features of that hypothesis, including the position of the butterflies, need revision, and (c) resolve the majority of family and subfamily relationships within superfamilies as thus far sampled. Much further gene and taxon sampling will be needed, however, to strongly resolve individual deeper nodes.
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    Biting Midges of the Genus Culicoides (Diptera: Ceratopogonidae) from Southwest Asia
    (1977) Navai, Shahin; Messersmith, Donald H.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    A study was made of the Southwest Asian species of the genus Culicoides Latreille 1809 from six countries: Afghanistan, Iran, Israel, Pakistan, Saudi Arabia and Turkey. Thirty-eight species of Culicoides belonging to seven subgenera: Trithecoides, Pontoculicoides, Avaritia, Culicoides, Oecacta, Beltranmyia and Monoculicoides are described and illustrated. A key is provided to the subgenera and slide mounted species of both sexes. Seven new species are described.
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    Studies on the Physiology of Hemolymph Coagulation in Perioplaneta Americana (L.)
    (1964) Wheeler, Ronald Earl; Jones, Jack Colvard; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    In the cockroach, Periplaneta americana (L.), hemolymph coagulation (a) is inhibited for as long as 30 minut es at 0° to 4°c, (b) is initiated at 5°c, (c) is permanently inhibited at 60°c, and (d) takes place in 6 distinct stages. Hemocyte agglutination and transformation is inhibited at 0° to 4°C, is permanently prevented at 55°c, and is independent of plasmal factors. Live plasmatocytes, granular hemocytes, and cystocytes are structurally identical, but differ functionally in their capacity to phagocytize and in their fragility. The cystocyte's primary function is the initiation of coagulation and/or precipitation of the plasma by ejecting cytoplasmic material, including mitochondria, into the surrounding plasma. Hemocyte-free plasma will not spontaneously precipitate, but requires either ionic calcium released from transforming hemocytes, and/or material from exploded cystocyte mitochondria . Substances inside mitochondria may well be t he source of a coagulation-inducing substance that initiates plasma precipitation and veil formation. Substances involved in P. americana coagulation are present in the plasma of 9 other species of cockroach which react to P. americana cystocytes. Substances in the plasma of Tenebrio molitor, Galleria mellonella, or Rhodnius prolixus do not precipitate in the presence of P. americana cystocytes. The amount and/or effectiveness of a coagulation-inducing substance released from cystocytes presumably determines the degree of plasma precipitation. Physiologically active substances contained in and/or released from the corpora allata and c. cardiaca, but lacking in the brain, may regulate the percentage of circulating cystocytes, thereby influencing the coagulability of the hemolymph.
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    Ecological Studies of Black Flies in Two Maryland Counties (Diptera:Simuliidae)
    (1957) McComb, William E.; Bickley, William E.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
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    On the Biology and Control of the North American Chestnut Weevils
    (1956) Johnson, Warren T.; Cory, E.N.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    Curculio auriger (Casey) and Curculio proboscideus Fab. are indigenous North American nut weevils and attack only the fruits of chestnut and chinquapin. Their natural distribution occurs over the same geographical areas that the American chestnut was found. Since the destruction of most of the native chestnut trees by chestnut blight, Endothia parasitica (Murr.), the weevils have been able to survive on scattered plantings of oriental chestnuts which are resistant to blight, from a few native chestnut trees partially resistant and from the coppice growth of old chestnut stumps. Rearing of both species in the field was accomplished by the use of soil cages set into the ground to a depth of 12 inches. Adult behavior was studied in large cages that completely covered the tree. Chestnut weevils lay their eggs in the kernel. The eggs of C. auriger hatch in about eight days and those of C. proboscideus hatch in about 10 days under the conditions in central Maryland. There are four larval instars in each species and these are described and illustrated. Head characters were found that will separate the species and the instars. C. auriger completes its larval development in 21 days while it takes 30 days for Q. proboscideus. The pupae of both species are of' the exerate type and may be separated by the presence of two small bristles on the beak, near the insertion of the antennae, of C. auriger. These bristles are lacking in C. proboscideus. The usual life cycle of C. auriger is two years. The life cycle of C. proboscideus is usually one year. A few individuals of each species require an additional year to complete their cycle. The adult C. auriger issues from the ground in May and feeds on the chestnut catkins. After the catkins wither they disperse and are not seen again until the chestnuts are nearing maturity. C. proboscideus issues from the ground late in July and may be seen in the trees a few days after emergence. The male genitalia were studied for taxonomic characters. These characters are sufficiently clear so that the two chestnut weevils may be identified thereby. Two species of internal insect parasites were found. Myiophasia nigrifrons Tns., a tachinid fly, was reared from the larvae of both species of' chestnut weevils and was observed in its larval stage within the body cavity of the chestnut weevil larva. Urosigalphus armatus Ashm. is a braconid parasite and was found only in the larvae of Q. prohoscideus. Chemical control studies have shown that the adult stage is the most susceptible to insecticides. Preliminary tests with heptachlor, applied at the rate of six to eight pounds of the chemical per acre, as a spray or dust to the ground cover under the trees, have given excellent results for the control of chestnut weevils.
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    INTEGRATED MANAGEMENT OF THE BOXWOOD LEAFMINER
    (1999) d'Eustachio, Gabriel John; Raupp, Michael J.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    Landscape managers need durable, effective, and safe methods for controlling key pests of valued plants in both landscape and nursery settings. The boxwood leafminer (Monarthropalpus flavus, Diptera: Cecidomyiidae) is a serious pest of boxwoods. Boxwoods (Buxus sp.) are a key plant in suburban Maryland landscapes. They are the second most common woody ornamental plant in these settings. In a recent study almost 43% of boxwoods surveyed required treatment for leafminer infestation. Boxwood leafminers also pose a serious problem in historical gardens, such as Longwood Gardens, PA, Dumbarton Oaks and the US National Arboretum in Washington, DC. At the present time, there is a lack of a comprehensive, environmentally sound, management program for the boxwood leafminer. The first step toward an effective management strategy is a better understanding of the boxwood leafminer's life cycle. Over the summers of 1994-1995, leafminer populations were surveyed and life cycles documented and correlated with growing degree days. The first growing degree day developmental chart for boxwood leafminer was developed. Various pesticides were tested in 1995. Different chemicals and application times were evaluated for control of both adults and larvae. At present it appears that application of a translaminar pesticide such as Avid or Merit at adult emergence (growing degree day 352) provides the best control. Resistant cultivars appear to be the most durable, simplest method to control the leafminer. Some cultivars.are highly resistant to boxwood leafminer attack while others are highly susceptible. The third goal of my project was to identify resistant cultivars. This was accomplished by first observing natural variation in leafminer populations in the field. Next I caged ovipositing adults on terminal branches of various cultivars of boxwood, and measured survival of larvae. All cultivars received heavy oviposition with equal frequency, although survival rates were very different. Finally, I tested the hypothesis that leafminers could discriminate among resistant and susceptible cultivars. To test this emerging adults were caged with different cultivars of boxwood and allowed to select plants for oviposition. Plants were then analyzed to determine acceptance of various host plants. I found that although survival on different cultivars can vary dramatically, leafminers were unable to distinguish between suitable and unsuitable host plants.
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    The Effect of Plant Nutrition on the Reproductive Rate and Susceptibility to Malathion of Two Strains of the Two-Spotted Spider Mite, Tetranychus telarius (L.)
    (1960) Henneberry, Thomas J.; Bickley, William E.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    Studies were conducted to determine the effect of plant nutrition on the reproductive rate and susceptibility to malathion of two strains of the two-spotted spider mite. The two strains of mites used as test organisms are characterized by their widely different levels of suscept­ibility to phosphate acaricides. Lima bean plants were grown in quartz sand and supplied nutrient solutions containing varying levels of nitrogen, phosphorus and potassium. Total nitrogen and total water soluble carbohydrate in the host plant tissue were determined by standard methods. Correlation analysis with the number of mite progeny and results of leaf analyses were conducted. The effects of plant nutrition on susceptibility to malathion of the two mite strains were determined by comparing per cent mortality data of mites from plants supplied the various nutrient solutions, Dosage-mortality responses of the two mite strains were also determined for mites of both strains from plants supplied nutrient solutions producing the greatest response in susceptibility. The reproductive rate of both strains increased as the supply and absorption of nitrogen increased. However, in studies with the resistant mite, a reduction in the number of progeny occurred on plants supplied the highest nitrogen level. The number of progeny of the malathion non­resistant mite were significantly correlated to increased nitrogen absorption. Increased reproductive rate of both strains was correlated to the carbohydrate present in the leaf tissue. When carbohydrate content in the leaf tissue was increased along with an increase in nitrogen supply and absorption the mite reproductive rate also increased. At still higher levels of nitrogen supply and absorption, carbohydrate content of leaf tissue decreased and the mite reproductive rate was depressed or failed to increase, The malathion non-resistant mite appeared more responsive to plants deficient in nitrogen than the resistant mite, On plants supplied the low nitrogen nutrient solutions, non-resistant mites failed to subsist, while the resistant mites maintained relatively high populations. The malathion non-resistant mite also produced more progeny on plants when phosphorus supply was increased. Populations of the resistant mite increased at higher levels of potassium. Phosphorus and potassium supply alone and in combination with certain levels of nitrogen affected nitrogen absorption and the relative amounts of carbohydrate present in the leaf tissue. Increasing the nitrogen supply to host plants resulted in increased susceptibility of the resistant mite to malathion. The non-resistant mite was more responsive to variations in phosphorus supply of host plants. A decrease in susceptibility followed an increase in phosphorus supply.