Chaoborus trivittatus

(Loew, 1862)

phantom midge

Chaoborus trivittatus is a of phantom midge, a non-biting fly in the Chaoboridae. The larvae are aquatic in lake , notable for their diel vertical between deep daytime and surface feeding zones. Unlike the congeneric C. americanus, C. trivittatus has a two-year with extended fourth-instar development. are short-lived and non-feeding.

Pronunciation

How to pronounce Chaoborus trivittatus: //kaɪˈoʊbɔːrəs trɪvɪˈtætəs//

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Identification

Larvae can be distinguished from Chaoborus americanus by capsule and size; C. trivittatus larvae have a two-year versus one year in C. americanus. Fourth-instar C. trivittatus larvae occur deeper than C. americanus during daytime but migrate less extensively at night. Macroscopic separation of larvae relies on head length and morphological characters described in taxonomic keys.

Habitat

Lacustrine environments, particularly deep lakes with thermal stratification. Larvae occupy the upper hypolimnion and metalimnion during daylight hours, typically below 5 meters depth in stratified lakes.

Distribution

Recorded from Eunice Lake, British Columbia, Canada; distribution beyond this locality is not documented in available sources.

Seasonality

occurs in late spring to early summer. Larvae are present year-round, in deep waters. Fourth-instar larvae show pronounced diel vertical during ice-free periods.

Diet

Zooplankton, primarily copepods (notably Diaptomus kenai) and cladocerans. Feeding occurs primarily at night in surface waters. Carbon assimilation of approximately 68% has been measured for both copepod and cladoceran prey.

Life Cycle

Two-year ; larvae overwinter twice before . First and second instars remain in upper 5 meters; third and fourth instars occupy deeper waters during day and migrate upward at night. Fourth instar persists through second year, accumulating approximately three-quarters of pupal weight during this stage. Pupation and occur in surface waters.

Behavior

Diel vertical : larvae ascend to surface waters at night to feed, then descend to deep, cold, often hypoxic waters during daylight. Migration is synchronous and regular, though the specific pattern does not match predicted energetically optimal strategies. are non-feeding with brief terrestrial phase for mating.

Ecological Role

in pelagic , contributing to top-down control of zooplankton . Vertical transports nutrients between deep and surface waters through and mortality. Serves as prey for fish when in surface waters; deep-water daytime reduces mortality.

Similar Taxa

Chaoborus americanusCo-occurs in same lakes; distinguished by one-year , more extensive vertical , and deeper daytime distribution; larvae separable by capsule