The bees of Niagara: a test of the intermediate disturbance hypothesis /

This study examined the bee fauna of the Carolinian Zone in Ontario, Canada. In 2003, 15687 individuals from 152 species of bees were collected. Tliere were many rare species but few abundant species. There were three distinct bee seasons. The Niagara bee assemblage was less diverse compared to other Carolinian Zone assemblages and types of landscapes. This study also examined how anthropogenic disturbance affects the diversity of bee assemblages. The intermediate disturbance hypothesis (IDH) was tested by selecting field sites subject to low, intermediate, and high disturbance. Intermediate disturbance had the highest species richness (SR=1 15) and most bees (N=556I), followed by low disturbance (SR= 100, N=2975), then high disturbance (SR=72, N=1364), supporting the IDH. Increased species richness in areas of intermediate disturbance was due to higher abundance, possibly because more blooming flowers were found there. Bees were larger in high disturbance areas but smaller in areas of high and intermediate disturbance.

Immunohistochemical study of laterodorsal tegmental neurons active during 22kHz vocalization /

An ascending cholinergic projection, which originates in the laterodorsal tegmental nucleus (LDT), was implicated in the initiation of ultrasonic vocalization. The goal of this study was to histochemically examine the activity the LDT following ultrasonic calls induced by two methods. It was hypothesized that cholinergic LDT cells would be more active during air puffinduced vocalization than carbachol-induced one. Choline acetyltransferase (ChAT), and cFos protein were visualized histochemically as markers of cholinergic calls and cellular activity, respectively. Results indicated that animals vocalizing after carbachol, but not after air puff, had a significantly higher number of Fos labeled nuclei within the LDT than non vocalizing controls. A significantly higher number of doublelabeled neurons were discovered in the LDT of vocalizing animals (in both groups) as compared to control conditions. Thus, there were significantly more active cholinergic cells in the LDT of vocalizing than non-vocalizing rats for both methods of call induction.

Mermithid (nematoa: mermithidae) infections of black flies (Diptera: Simuliidae) : seasonal variation and developmental characteristics /

Mermithid nematodes (Nematoda: Mermithidae) parasitize larval, pupal and adult black flies (Diptera: Simuliidae), oftentimes resulting in partial or complete host feminization. This study was designed to characterize parasite-host seasonal variation and to estabUsh the developmental life stage at which feminization is initiated. Data indicate that the total adult population of black flies collected from Algonquin Provincial Park throughout the spring of 2004 was comprised of 31.8% female, 67.8% male and 0.4% intersex individuals. Of the total population, 0.6% was infected by mermithid nematodes (69.0% female, 3.5% male and 27.6% intersex). Seasonal infection trends established over a 12-month period revealed that black flies with different life histories host the same mermithid subfamilies, while black flies with similar life histories host mermithids from different subfamilies. If a simuliid species simultaneously hosts two mermithid species, these parasites are from different subfamilies. Molecular mermithid identification revealed two mermithid subfamilies, Me.somermithinae and Gastromermithinae, present in the simuliid hosts. Mermithid colour variation was not found to be a reliable species indicator. The developmental stage at which feminization is initiated was determined by examining gonad morphology and meiotic chromosomal condition. Results indicate that mermithid-infected black flies exhibit feminization prior to larval histoblast formation. Larvae can be morphologically male (testes present) or female (ovaries present), with morphological males exhibiting either male (achiasmate) or female (chiasmate) meiotic chromosomes; morphological females were only genetically female. Additionally, mermithid infection inhibits simuliid gonad development.

Localization and functional characterization of iridoid biosynthetic genes in Catharanthus roseus /

Catharanthus roseus is the sole biological source of the medicinal compounds vinblastine and vincristine. These chemotherapeutic compounds are produced in the aerial organs of the plant, however they accumulate in small amounts constituting only about 0.0002% of the fresh weight of the leaf. Their limited biological supply and high economical value makes its biosynthesis important to study. Vinblastine and vincristine are dimeric monoterpene indole alkaloids, which consists of two monomers vindoline and catharanthine. The monoterpene indole alkaloids (MIA's) contain a monoterpene moiety which is derived from the iridoid secologanin and an indole moiety tryptamine derived from the amino acid tryptophan. The biosynthesis of the monoterpene indole alkaloids has been localized to at least three cell types namely, the epidermis, the laticifer and the internal phloem assisted parenchyma. Carborundum abrasion (CA) technique was developed to selectively harvest epidermis enriched plant material. This technique can be used to harvest metabolites, protein or RNA. Sequencing of an expressed sequence tagged (EST) library from epidermis enriched mRNA demonstrated that this cell type is active in synthesizing a variety of secondary metabolites namely, flavonoids, lipids, triterpenes and monoterpene indole alkaloids. Virtually all of the known genes involved in monterpene indole alkaloid biosynthesis were sequenced from this library.This EST library is a source for many candidate genes involved in MIA biosynthesis. A contig derived from 12 EST's had high similarity (E'^') to a salicylic acid methyltransferase. Cloning and functional characterization of this gene revealed that it was the carboxyl methyltransferase imethyltransferase (LAMT). In planta characterization of LAMT revealed that it has a 10- fold enrichment in the leaf epidermis as compared to the whole leaf specific activity. Characterization of the recombinant enzyme revealed that vLAMT has a narrow substate specificity as it only accepts loganic acid (100%) and secologanic acid (10%) as substrates. rLAMT has a high Km value for its substrate loganic acid (14.76 mM) and shows strong product inhibition for loganin (Kj 215 |iM). The strong product inhibition and low affinity for its substrate may suggest why the iridoid moiety is the limiting factor in monoterpene indole alkaloid biosynthesis. Metabolite profiling of C. roseus organs shows that secologanin accumulates within these organs and constitutues 0.07- 0.45% of the fresh weight; however loganin does not accumulate within these organs suggesting that the product inhibition of loganin with LAMT is not physiologically relevant. The limiting factor to iridoid and MIA biosynthesis seems to be related to the spatial separation of secologanin and the MIA pathway, although secologanin is synthesized in the epidermis, only 2-5% of the total secologanin is found in the epidermis while the remaining secologanin is found within the leaf body inaccessable to alkaloid biosynthesis. These studies emphasize the biochemical specialization of the epidermis for the production of secondary metabolites. The epidermal cells synthesize metabolites that are sequestered within the plant and metabolites that are secreted to the leaf surface. The secreted metabolites comprise the epidermome, a layer separating the plant from its environment.

Genetic variation and evolutionary divergence within and among populations, species, and genera of the Cambarinae

Seven crayfish species from three genera of the subfamily Cambarinae were electrophoretically examined for genetic variation at a total of twenty-six loci. Polymorphism was detected primarily at three loci: Ao-2, Lap, and Pgi. The average heterozygosities over-all loci for each species were found to be very low when compared to most other invertebrate species that have been examined electrophoretically. With the exception of Cambarus bartoni, the interpopulation genetic identities are high within any given species. The average interspecific identities are somewhat lower and the average intergeneric identities are lower still. Populations, species and genera conform to the expected taxonomic progression. The two samples of ~ bartoni show high genetic similarity at only 50 percent of the loci compared. Locus by locus identity comparisons among species yield U-shaped distributions of genetic identities. Construction of a phylogenetic dendrogram using species mean genetic distances values shows that species grouping is in agreement with morphological taxonomy with the exception of the high similarity between Orconectespropinquus and Procambarus pictus. This high similarity suggests the possibility of a regulatory change between the two species. It appears that the low heterozygosities, high interpopulation genetic identities, and taxonomic mispositioning can all be explained on the basis of low mutation rates.

A biochemical predictor of performance during mesophilic anaerobic fermentation of starch wastewater

The aim of this study was to determine the potential of biochemical parameters, such as enzyme activity and adenosine triphosphate (ATP) levels, as monitors of process performance in the Upflow Anaerobic Sludge Blanket (UASB) reactor utilizing a starch wastewater. The acid and alkaline phosphatase activity and the ATP content of the UASB sludge were measured in response to changes in flow rate and nutrient loading. Conventional parameters of process performance, such as gas production, acetic acid production, COD, phosphorus, nitrogen and suspended solids loadings and % COD removal were also monitored. The response of both biochemical and conventional parameters to changing process conditions was then compared. Alkaline phosphatase activity exhibited the highest activity over the entire study perioda A high suspended solids loading was observed to upset the system in terms of gas production, acetic acid production and % COD removala The initial rate of increase in alkaline phosphatase activity following an increase in loading was four times as great during process upset than under conditions of good performance. The change in enzyme actiVity was also more sensitive to process upset than changes in acetic acid production. The change in ATP content of the sludge with time suggested that enzyme actiVity was changing independently of the actual viable biomass present. The bacterial composition of the anaerobic sludge granules was similar to that of other sludge bed systems, at the light and scanning electron microscope level. Isolated serum bottle cultures produced several acids involved in anaerobic carbohydrate metabolism. The overall performance of the UASB system indicated that higher loadings of soluble nutrients could have been tolerated by the system.

A comparative study of chitin synthase activity in two Mortierella species

An in vitro investigation of some important factors controlling the activity of chitin synthase in cell-free extracts of two Mortierella species has been carried out. Mixed membrane fractions from mycelial homogenates of Mortierella candelabrum and Mortierella pusilla were found to catalyse the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine into an insoluble product characterized as chitin by its insolubility in weak acid and alkali, and the release of glucosamine and diacetylchitobiose on hydrolysis with a strong acid and chitinase, respectively. Apparent Km values for UDP-GlcNAc were 1.8 mM and 2.0 mM for M. pusilla and ~ candelabrum, respectively. Polyoxin D was found to be a very potent competitive inhibitor with values of the constant of inhibition, Ki' for both species about three orders of magnitude lower than theKm for UDP-GlcNAc. A divalent cation, Mg+2 , Mn+2 or Co+2 , was required for activity. N-acetylglucosamine, the monomer of chitin, stimulated the activity of the enzyme. The crude enzyme preparation of ~ candelabrum, unlike that of ~ pusilla, showed an absolute requirement for both Mg+2 and N-acetylglucosamine. Large differences in response to exogenous proteases were noted in the ratio of active to inactive chitin synthase of the two species. A fifteen fold or greater increase was obtained after treatment with acid protease (from Aspergillussaitoi) as compared to a two- to four-fold activation of the M. pusilla membrane preparation treated similarly. During storage at 4°C over 48 hours, an endogenous activation of chitin synthase of ~ pus ilIa was achieved, comparable to that obtained by exogenous protease treatment. The high speed supernatant of both species inhibited the chitin synthase activity of the mixed membrane fractions. The inhibitor of ~ pus ilIa was effective against the pre-activated enzyme whereas that of M. candelabrum inhibited the activated enzyme. Several possibilities are discussed as to the role of the different factors regulating the enzyme activity. The suggestion is made from the properties of chitin synthase in the two species that in vivo a delicate balance exists between the activation and inactivation of the enzyme which is responsible for the pattern of wall growth of each fungus.

A comparative study of in vitro chitin synthase activity in mucoraceous hosts of a mycoparasite

A comparative study of in vitro chitin synthase activity in mucoraceous hosts of a mycoparasite: Chitin synthase, the enzyme responsible for the synthesis of chitin in fungal cell wall was extracted from young hyphae of Choanephora cucurbitarum and Phascolomyces articulosus, susceptible and resistant hosts, respectively, to the mycoparasite, Piptocephalis virginiana. Crude enzyme was identified and characterized by measuring the incorporation of the substrate [14C]-UDP-N-acetylglucosamine, into chitin. Most activity occurred in mixed membrane fraction. Inhibition of activity with Polyoxin D and activation with proteases, N-acetyl-glucosamine and magnesium and other ions was observed. Properties of the crude enzyme preparation such as cofactor requirement, Vmax , apparent Km value for UDP-GlcNAc, inhibition by Polyoxin D, response to pH and to temperature, and stability at 4°C were determined. Enzyme activity from both fungi displayed basically the same features as the corresponding enzymes reported from other mucoraceous fungi. However, the two preparations from P. articulosus and C. cucurbitarum differed from each other in their expressed activity (i.e., the preparations from ~ articulosus exhibited higher latency and higher specific chitin synthase activity than the corresponding preparations from ~ cucurbitarum). Trypsin was effective in activation only over a narrow concentration range. Acid protease was the most effec.tive activator. En.dogenous protease estimation indicated higher protease activity in C. cucurbitarum than in P. articulosus. The suggestion is made that regulation of chitin synthase activities may be related to host resistance in the mycoparasitic system.

A comparative study of protoheme and heme d catalases : role of the heme and the heme pocket in catalysis and ligand binding

Catalase dismutes H20 2 to O2 and H20. In successive twoelectron reactions H20 2 induces both oxidation and reduction at the heme group. In the first step the protoheme prosthetic group of beef liver catalase forms compound I, in which the heme has been oxidized from Fe3+ to Fe4+=0 and a porphyrin radical has been created. Compound II is formed by the oneelectron reduction of comp I. It retains Fe4+=0 but lacks the porphyrin radical and is catalytically inert. Molecular structures are available for Escherichia coli Hydroperoxidase II, Micrococcus Iysodeiktus, Penicillium vitale and beef liver enzymes, which contain different hemes and heme pockets. In the present work, the pockets and substrate access channels of protoheme (beef liver & Micrococcus) and heme d (HPII of E. coli and Penicillium) catalases have been analysed using Quanta™ and CharmMTM molecular modeling packages on the Silicon Graphics Iris Indigo 2 computer. Experimental studies have been carried out with two catalases, HPII (and its mutants) and beef liver. Fluoride and formate' are inhibitors of both enzymes, and their binding is modulated by the heme and by distal residues N201 & H128. Both HPII and beef liver enzymes form compound I with H202 or peracetate. The reduction of beef liver enzyme compound I to II and the decay of compound II are accelerated by fluoride. The decay of compound II is also accelerated by formate, and this reagent acts as a 2-electron donor towards compound I of both enzymes. It is concluded that heme d enzymes (Penicillium and HPII of E. coli) are formed by autocatalytic transformation of protoheme in a modified pocket which contains a characteristic serine residue as well as a partially occluded heme channel. They are less active than protoheme enzymes but also do not form the inactive compound II species. Binding of peroxide as well as fluoride and formate is prevented by mutation of H128 and modulated by mutation of N201.

A cytophylogenetic study of Pacific black flies (Diptera: Simuliidae)

The sequential banding patterns of the larval salivary gland polytene chromosomes of seven species of Inseliellum (Diptera: Simuliidae) were mapped. This was completed through the comparison with the standard maps of an eighth species of Inseliellum, Simulium cataractarum. During chromosomal analysis, both fixed and floating inversions were identified. A floating inversion (IIL-l ex,2ex) revealed a cytotype within Simulium exasperans that is distributed between two islands, Moorea and Tahiti. Inversion data revealed three shared fixed inversions that could be used as phylogenetic characters. In addition, the placement of a chromosomal landmark (the nucleolar organizer, or NO) was used as a phylogenetic character. The result of a cytophylogenetic (transformational) analysis showed two groups: the NO-IL group, and the NO-IS group. A combined phylogeny was created using the published morphological data and the cytological data of the eight species. The combined tree did not differ from the morphological data only tree. Possible routes of dispersal are hypothesized using geological, chromosomal, and phylogenetic data. These data showed a general pattern of dispersal and colonization from older islands to younger islands, with one possible instance of dispersal from younger to older islands. It is postulated that inter-island speciation has allowed this dispersal and colonization, but intra-island speciation has created the diversity seen in Inseliellum.

Alicaligenes faecalis : identification and study of its antagonistic properties against Botrytis cinerea

A Gram negative aerobic flagellated bacterium with fungal growth inhibitory properties was isolated from a culture of Trichoderma harzianum. According to its cultural characteristics and biochemical properties it was identified as a strain of Alcaligenes (aeca/is Castellani and Chalmers. Antisera prepared in Balbc mice injected with live and heat-killed bacterial cells gave strong reactions with the homologous immunogen and with ATCC 15554, the type strain of A. taeca/is, but not with Escherichia coli or Enterobacter aerogens in immunoprecipitation and dot immunobinding assays. Growth of Botrytis cinerea Pers. and several other fungi was significantly affected when co-cultured with A. taeca/is on solid media. Its detrimental effect on germination and growth of B. cinerea has been found to be associated with antifungal substances produced by the bacterium and released into the growth medium. A biotest for the antibiotic substances, based on their inhibitory effect on germination of B. cinerea conidia, was developed. This biotest was used to study the properties of these substances, the conditions in which they are produced, and to monitor the steps of their separation during extraction procedures. It has been found that at least two substances could be involved in the antagonistic interaction. One of these is a basic volatile substance and has been identified as ammonia. The other substance is a nonvolatile, dialysable, heat stable, polar compound released into the growth medium. After separation of growth medium samples by Sephadex G-10 column chromatography a single peak with a molecular weight below 700 Daltons exhibited inhibitory activity. From its behaviour in electrophoretic separation in agarose gels it seems that this is a neutral or slightly positively charged.

Amplification of the DFR1 gene in Saccaromyces cerevisiae

A new system was employed to study amplification of t,he DHF'R gene DFB,1 ) in Sa<,:;charoillYCB§. .Q~~Yi...S!i<;1~. . This system consists of a series of yeast strains containing a casset,te which encodes t he yeast, D..ERl gene ttghtly linked tjO a f usion of the yeast 1EU2. regulat,ory region wi tJ1 the LAQZ str ctural gene from E. cO.1-1 (,) . M. Clement , unpubl i,::;hed) . Th's casset;t e was shown t.o be integrat,ed int o a unj que chromosomal l ocati on in each strain . Yeast cells were se l ected for MTX-resistance and overproduction of ~ galac t osi d se ( B-gal ). Since the inserted DF'Rl and ~ACZ genes are independently regulated, it was thought that cel l s with this phenotype probably contain e d ampl if ications of the cassette. A lar ge variat ion in the f requn y o f MTX-resistance was found between the di ff e r ent str ains. These freqlen c ~ es r anged from about 2 x 10 - 7 fo r a population of cells containing the cassette integrated at, the BI J2.l gene in t,he middle of the long arm of chromosome V, to about 5 x 10-4 for a strain with the cassette i nserted in the r DNA cluster Abo It 85% of the MTX- res i stcmt iso l ates examined showed enhanced B·-gal act i v ity rel a t ive t o the parental strain . For the ma jorit y of strains, the mean B- gal activity in drug-r sistant clones was about 3 times that o f the parent following a single se l ect i on step . I n con t r ast, primary MTX-resistant derivat~ves of cells with the cassette inserted 3 at the rDNA cluster showed inc r eases in B- gal activity ranging from 9 - 14 f old r elative to the parent. Analysis of the latte r s train by Southe rn hybr idization indicated that the cassette was inde e d amplified several fold in MTX-re sistant derivatives. A sing l e strain, in which the cassette was inserted at the !lEA;], loc u.s , was used to examine in more detai 1 , the parameters affecting DFRl gene amplificat~ion in yeast . The mean B- gal activity in drug-resistant derivatives of this strain could be increased from 3 to 6 or 7 fold relative to the parent, by stepwise sel ection using increasing MTX concentrations. B-gal overproduction was found to be un stable in all primary and highly -resistant isolates examined. There was no indication, h owever, of a decrease i n growth r a t e in MTX-res i s tant cells which overproduced B - gal.

Amputation and heat induced protein synthesis in the regenerating forelimb of Notophthalmus viridescens

This thesis compares the responses of regenerating forelimb tissues of the newt Notophthalmu..f vlridescens to the stresses of hyperthermia and ID.echanical injury of amputation. In particular, both quantitative and qualitative changes in the synthesis of soluble proteins in stump tissues, including those of the heat shock protein family (HSP70-1ike) were examined. Results from SDS-PAGEfluorography indicate that the trauma of amputation mimics the heat shock response both quantitatively and temporally in its transient repression of the synthesis of most normal cellular proteins, and qualitatively. in the locaJized expression of two unique proteins (hsp30 and hsp70). Fluorography of proteins separated by twodimensional gets revealed that thelCl4:alizedt amputation induced 70kDa protein (amp70) was distinct from the more basic newt hsp/hsc70 isoforms. Although limb amputation resulted in an increase in the synthesis of HSP70 mRNA analogous to that induced by heat 3.b.OCKf amp70 did not cross-react with murine monoclonal antibodies directed against both the inducible and cognate HSP70 proteins of the human. Thus, the possible relationship of amp70 to other members of the HSP70-1ike protein family remains unclear. Western analyses indicated that the levels of the constitutive form of HSP70 (hsc70) were found to be regulated in a stage-dependent manner in the distal stump tissues of the regen,erating forelimb of the newt. The highest levels were found in the mid-late bud stage, a period during which rapidly dividing blastema cells begin to redifferentiate in a proximodistal direction. Immediately after amputation) hsc70 synthesis and accumulation was depressed below steady-state levels measured in the unamputated limb~ The results are discussed in light of a possible role for HSPs and amputatio~ induced proteins in the epimorphic regeneration of the amphibian limb.

Analysis of a temperature sensitive mutation affecting aldehyde oxidase activity in Drosophila melanogaster

A strain of Drosophila melanogaster (mid america stock culture no. hl16) has been reported to be deficient in aldehyde oxidase activity (Hickey and Singh 1982). This strain was characterized during the course of this study and compared to other mutant strains known to be deficient in aldehyde oxidase activity. During the course of this investigation, the hl16 strain was found to be temperature sensitive in its viability. It was found that the two phenotypes, the enzyme deficiency, and the temperature sensitive lethality were the result of two different mutations, both mapping to the X-chromosome. These two mutations were found to be separable by recombination. The enzyme deficiency was found to map to the same locus as the cinnamon mutation, another mutation which affects aldehyde oxidase production. The developmental profile of aldehyde oxidase in the hl16 strain was compared to the developmental profile in the Canton S wild type strain. The aldehyde oxidase activity in adult hl16 individuals was also compared to that of various other strains. It was also found that the aldehyde oxidase activity was temperature sensitive in the adult flies. The temperature sensitive lethality mutation was mapped to position 1-0.1.

An investigation of sugar feeding by black flies (Diptera: Simuliidae)

Although much research has been conducted on blood-meal acquisition in adult female black flies (Diptera: Simuliidae), the same cannot be said for sugarmeals. Both sexes feed on sugar which provides energy for flight and it has been commonly held that nectar is the major carbohydrate source. This thesis addresses the question of whether a non-floral carbohydrate source, specifically homopteran honeydew, is ingested by male and female black flies. Black flies reared in the laboratory have been observed to readily ingest freshly excreted and older (dry) honeydew when presented with honeydew coated tamarack branches. Field work was conducted in Algonquin Park, Ontario in the spring and summer of 1993. Three separate studies were designed to test whether homopteran honeydew is an important carbohydrate source for black flies and whether flies from different habitats utilize different sugar sources. The sugars melezitose and / or stachyose are known to occur in a variety of homopteran honeydews and therefore were used as indicators of honeydew feeding by black flies. In the first study, black flies were collected with insect nets from a stand of Larix larcina heavily infested with honeydew - producing homopterans (Adelges lariciatus). Six black fly species were captured: Simulium venustum, S. rostra tum, S. vittatum, Stegopterna mutata, S. aureum and S. quebecense. Samples of honeydew and individual black flies were tested using thin layer chromatography (T. L. C.) with fructose, glucose, sucrose, turanose, melezitose, raffinose and stachyose as standards. All sugars except turanose and melezitose were found in the adelgid honeydew samples. Since the sugar melezitose was absent from ~ honeydew samples, stachyose was used to indicate that black flies were feeding from this particular honeydew source. Of the 201 black flies tested, 194 contained sugars which occurred in 16 combinations. Stachyose combinations excluding melezitose, present in 45.9 % of flies, were used to indicate that black flies had been feeding on the adelgid honeydew. In the second study, black flies were collected in the morning and evening on 8 collection dates, using a vehicle mounted insect net. The crops and midguts of 10 male and 10 female Simulium venustum were dissected on each sample date. In total the gut contents of 320 individual flies were analysed by T. L. C. The sugars identified from these flies were present in the following proportions: fructose (100.0%), glucose (100.0%), sucrose/turanose (50.4%), melezitose (30.3%), raffinose (18.8%) and stachyose (8.7%). These sugars occurred in fourteen different combinations. It is argued that the presence of melezitose and / or stachyose indicates that black flies had fed on homopteran honeydew. Significantly more female flies (40.0%) than male flies (27.5%) had fed on honeydew. In the third study, adult black flies were sampled by sweep netting vegetation in four habitats in the morning and evening on 8 collection dates. The habitats are as follows: (1) Davies Bog, (2) Abandoned Air Field (dominated by blueberries, Vaccinium spp.), (3) Deciduous Habitat and (4) Coniferous Habitat. Sugars in the crops and midguts of female flies were tested by T. L. C. and, for S. venustum, it was found that significantly fewer flies (18.8%) from the Air Field contained honeydew than from the other three sites (Davies Bog, 34.4%; Deciduous Habitat, 36.2%; Coniferous Habitat, 25.0%). Of the 1287 black flies tested individually by T. L. C. 441 (34.3%) contained melezitose and / or stachyose sugars indicating that this proportion of the population were feeding from Homopteran honeydew. It is therefore clear that floral (nectar) sugars are not the only source of carbohydrates available to black flies.