Andrew E. Rosselot

Fungicide Contamination Reduces Beneficial Fungi in Bee Bread Based on an Area-Wide Field Study in Honey Bee, Apis mellifera, Colonies

Fermentation by fungi converts stored pollen into bee bread that is fed to honey bee larvae, Apis mellifera, so the diversity of fungi in bee bread may be related to its food value. To explore the relationship between fungicide exposure and bee bread fungi, samples of bee bread collected from bee colonies pollinating orchards from 7 locations over 2 years were analyzed for fungicide residues and fungus composition. There were detectable levels of fungicides from regions that were sprayed before bloom. An organic orchard had the highest quantity and variety of fungicides, likely due to the presence of treated orchards within bees’ flight range. Aspergillus, Penicillium, Rhizopus, and Cladosporium (beneficial fungi) were the primary fungal isolates found, regardless of habitat differences. There was some variation in fungal components amongst colonies, even within the same apiary. The variable components were Absidia, Alternaria, Aureobasidium, Bipolaris, Fusarium, Geotrichum, Mucor, Nigrospora, Paecilomyces, Scopulariopsis, and Trichoderma. The number of fungal isolates was reduced as an effect of fungicide contamination. Aspergillus abundance was particularly affected by increased fungicide levels, as indicated by Simpsons diversity index. Bee bread showing fungicide contamination originated from colonies, many of which showed chalkbrood symptoms.

High temperature and dehydration tolerance of the red velvet mite, Balaustium sp. (Erythraeidae), permit the exploitation of extremely hot, dry microhabitats

Red velvet mites Balaustium sp. nr. putmani, a mite commonly associated with landscaping projects throughout the Midwestern United States, show a particular affinity for warm, sunny locations. Adults display a remarkable tolerance for high temperature, capable of actively crawling on extremely hot surfaces for extended periods. To determine the upper thermal tolerance of this mite, we compared short-term 1-hour heat-shock responses, coupled with a behavioural scoring system, among all mobile instars (larva, deutonymph and adult) that occur on hot surfaces. Maximum heat shock for 50% survival was 48°C for larvae, 52°C for deutonymphs and 52–54°C for adults, which is high for an acarine and indicates that the active instars of this mite are generally resistant to heat stress. Larvae experienced their first major drop in survival of ≥20% between 42°C and 44°C; this drop occurred at 48–50°C for deutonymphs and 50–52°C for adults. A distinguishing feature of deutonymphs and adults is their ability to recover from heat-induced injury, something that larvae apparently lack. This recovery is characterized by an abrupt injury/mortality at 52°C (nearly all survive heat shocks of 40–48°C) for adults and deutonymphs, whereas the response in larvae is graded following a dose–response from 42°C to 50°C. Our conclusion is that enhanced high-temperature tolerance coincides with heat-shock recovery in deutonymphs and adults that are active for longer periods of time during the hottest periods each year. The larval season occurs early during the cooler spring, which facilitates the establishment of populations. Balaustium sp. nr. putmani requires a dry habitat to function properly. It seems reasonable to suggest that sunny sites create ideal dry habitats for B. sp. nr. putmani to thrive, and increased sun exposure at these preferred dry sites simultaneously requires that these mites are heat tolerant.

Pollen feeding in Balaustium murorum (Acari: Erythraeidae): visualization and behaviour

To determine whether pollen is a significant food source for Balaustium cf. murorum (tentative identification), behavioural responses to pollen feeding were examined in short-range Petri plate bioassays. Evans blue dye was used as a tracer to stain pollen after being incorporated into the gut. The results show that all active stages (larva, deutonymph and adult) ingested whole pollen from viburnum shrub (Viburnum) and daffodil (Narcissus) cultivars. All active stages fed on all types of pollen tested: tulip (Tulipa), daffodil (Narcissus), pear (Pyrus), maple (Acer), viburnum (Viburnum) and crabapple (Malus) cultivars except for tulip in the adult and tulip, pear and crabapple in the deutonymph. A higher percentage of larvae fed on pollen-covered surfaces and cleared pollen at a faster rate than other life stages in the bioassays. Clearance of viburnum and daffodil pollen by larvae and deutonymphs was particularly rapid, but this shifted to maple and crabapple pollen in the adult. In pheromone bioassays, pollen-fed larvae, deutonymphs and adults did not prompt clustering or avoidance by free-ranging mites. Our conclusion is that B. murorum can feed on pollen from different sources, no attraction-aggregation pheromone or alarm pheromone is emitted by fed mites and pollen feeding is more important for larvae that emerge in early spring when other food options are scarce.

Water balance characteristics of pupae developing in different size maggot masses from six species of forensically important flies

The impact of maggot mass size on body water content, net transpiration rate, and dehydration tolerance of fly pupae was examined in six species of necrophagous flies. Species that spent more time on food as larvae, produced pupae with high body water contents. Dehydration tolerance limits of pupae were modest, matching the moisture-rich conditions of decaying carrion for larvae. Protophormia terraenovae pupariates on food as it dries, and this was reflected by pupae having the highest body water content and lowest net transpiration rate. Megaselia scalaris featured the lowest body water content and highest dehydration tolerance, implying that this species is arid-suited, which matches its ability to feed and colonize on post-decay carrion. Lucilia illustris was the most sensitive to larval overcrowding, resulting in a dramatic decrease in pupal size, early dispersal from food, fed less and had fast net transpiration rates. By contrast, Lucilia sericata was the most resistant, by showing no pupal size decrease and no change in net transpiration rate. Other species were between these extremes, requiring larger maggot mass sizes to produce the effect of decreasing pupal size and increasing net transpiration rate. We conclude: (1) the pupas response to overcrowding and water balance profile are species-specific, varying according to pupal size and net transpiration rate as independent characteristics; (2) water balance profile of the pupae reflects the behavior and microhabitat of the larva; and (3) danger of lethal desiccation to smaller-sized pupae is circumvented by a faster developmental rate rather than enhanced water conservation.

Knot formation reduces water exchange by adult males of the hairworm, Paragordius varius (Nematomorpha: Gordioidea)

To examine how aggregation by hairworms may enhance survival in freshwater, we determined water balance characteristics of Paragordius varius in groups of different sizes. P. varius is hyperosmotic resulting in high body water content and functions down to one-half of water stores. Absence of a critical transition temperature implies a watertight, low-porosity cuticle. Aggregated worms lose water slowly, as a physiological consequence of reduced motor activity. The water balance strategy shifts from a reliance on high dehydration tolerance for isolated individuals, affording high water loss rates, to suppressed activation energy when aggregated, wherein blocking water gain is important when water loss is slower. Low water loss rate derives from stillness and aggregating that facilitate mating or anti-predator defense, rather than as a behavior to regulate water loss. Presence of hairworms in streams is an indicator of high-quality water that is necessary to maintain water balance.

Rearing and storage in mung beans reduce medically significant molds by the seed beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae), utilized in science classrooms

To examine whether colonies of seed beetles, Callosobruchus maculatus, may be a health concern as a source of mold allergens to students and teachers, we compared the amount and type of molds present on adult beetles reared with mung beans and cowpeas, Vigna radiata and Vigna unguiculata, respectively (Family Fabaceae). Specimens were analyzed from two elementary schools, a commercial supplier and a university insectary. A total of nine fungal genera were isolated from live and dead adult beetles, consisting primarily of Aspergillus (a large proportion of which was Aspergillus niger) and Penicillium, with lower, variable numbers of Alternaria, Cladosporium, Fusarium, Mucor, Rhizopus, Scopulariopsis, and Trichoderma. Absidia, Geotrichum, and Paecilomyces were additional genera isolated from dead beetles. These molds are medically significant as potential allergens, and others (Aspergillus, Rhizopus, Mucor) can cause secondary infections in people. The mold profile of different beetle colonies are similar in quality and quantity, thus suggesting that beetles are acquiring molds that are commonly found or can develop on seeds in their rearing/storage containers. Rearing on mung beans suppresses total mold growth by nearly 63% compared to the amount observed when raised on cowpeas. In fact, most cultures of beetles reared in mung beans were entirely fungus-free. Our conclusion is that the amount and diversity of allergenic molds from seed beetles for use in classrooms can be minimized considerably by using mung beans for beetle rearing, along with routine colony maintenance and proper hygiene.