Lordotus pulchrissimus

Lordotus pulchrissimus has a signature coat of yellowish fur, clear wings, and large brown eyes. The fly also has a notable proboscis, which is used for collecting nectar from flowering desert brush.[7] Both sexes of L. pulchrissimus are hairy, which distinguishes them from the bare but otherwise very similar species, L. luteolus.[7] L. pulchrissimus is a relatively large bee fly compared to other flies in its family.[5] The males and females are distinct in appearance, which caused them to be misidentified as different species in the past.[8]

Male L. pulchrissimus have been found to range from 8-16 millimeters in length. They have considerably less fur than the females in addition to larger wingspans.[5] The males' fur typically ranges from yellow to brown in color. They have characteristic black markings on much of their femora.[8]

Female L. pulchrissimus have been found to range from 2-14 millimeters in length.[5] Females typically have more dense fur than males in addition to brighter shades of orange and yellow fur.[8]

An interesting aspect of female L. pulchrissimus is the color change of their fur. Not only does the fur coat of females age more rapidly than males as they age, the color of their fur when the female is alive fades more quickly than when they are dead. This feature of female's fur was used as a study's metric in determining their age in study, as the females' fur tends to fade at similar rates.[6]

Lordotus pulchrissimus' activity distributions are notably different from other flies who have ecologically similar requirements and live in similar habitats. They engage in feeding, as well as more aggressive behavior, primarily in the morning time and for very lengthy periods of time. In comparison, most other flies inhabit similar climates and intersperse these energy-costly activities with resting periods throughout the day. This behavior in most flies is more energy efficient than the activity budgeting of L. pulchrissimus, which starts expending energy at the beginning of the day.[5]

Observations of male L. pulchrissimus demonstrate the different activity budgeting, who allocate more of their time to energetically costly activities than almost any other species of fly; they spend a majority of their time doing energy-costly activities like engaging in continuous hover flight and lengthy aerial aggregations. While males typically forage somewhat less than females, they use their extra time for more aggregation rather than more rest. Although this behavior could be described as lekking, not enough is known about it to determine the underlying causes.

The most notable behavior pattern that male L. pulchrissimus exhibit is their daily aggregation into aerial swarms on stabilized dunes. This behavior has been primarily studied on the north shore of Mono Lake in California.[6] Although on a given day, males typically arrive first to the swarm area and begin interacting before females arrive, the pattern of male aggregation in L. pulchrissimus is especially distinct as this type of male aggregation typically has more costs than benefits. In most other cases where males aggregate, it occurs as a result of female aggregation, but this is not the case for L. pulchrissimus. The aggregation typically occurs over areas of relatively sparse rabbitbrush, showing that the male aggregation is also unrelated to obtaining resources. Most cases of male aggregation occur in concordance with female aggregation and/or resource density, but neither is the case for L. pulchrissimus.[5][6]

L. pulchrissimus typically stay within a few hundred square meters of sites of male aggregation, unique because males tend to avoid areas of high resource density when aggregating. The males tend to occupy areas very close to their aggregation sites. The home range of females, however, has not been researched, as their recapture in most studies was relatively unsuccessful compared to males. The females tend to migrate away approximately 70 meters each day, and are not guaranteed to return to the spot they were at the previous day.[6]

Conversely to other species of fly in their areas of inhabitance, L. pulchrissimus males do not typically express territoriality over a single brush bush. L. pulchrissimus males, instead, spend approximately 1.5 hours each day aggregating about 20 meters in the air above areas of brush. However, during these aggregations, the males vigorously defend their territory and engage in aggressive behavior while in their aggregation clouds.[5]

The population density of female L. pulchrissimus is higher than the population density of male L. pulchrissimus. Males typically are found at a population density of 2-5 males per hectare. For females, the distribution of ages is biased towards younger females as they typically leave the group after mating. Females live approximately 10–14 days. Less information is given on male population structure, as the study focused more on the presence and absence of females.[6]

L. pulchrissimus larvae feed on the flesh and eggs of other insects. The specific insects they feed on are currently unknown.[5]

Bee fly larvae often parasitize the immature stages of other insects for sustenance.[5] Bee fly larvae are parasitoids which take extreme advantage of their hosts, often feeding on them or their eggs.[5]

Adult L. pulchrissimus feed mostly on desert brush.[7]

In one of the primary sites of L. pulchrissimus research in Mono Lake, CA, the adult diet consists almost entirely on Chrysothamnus nauseosus or rabbitbrush, a flowering perennial shrub that attracts many different types of pollinating insects. L. pulchrissimus allocate more of their time to feeding than is common for fly species, converse to the concept that they should be foraging-time minimizers. The reason for this is not yet researched.[5]

L. pulchrissimus have a mutualistic relationship with rabbitbrush. The flies feed on its nectar and pollinate the brush in the process.[5]