{"id":4285,"date":"2012-02-14T14:11:47","date_gmt":"2012-02-14T20:11:47","guid":{"rendered":"https:\/\/uwm.edu\/field-station\/?p=4285"},"modified":"2017-05-20T15:22:47","modified_gmt":"2017-05-20T20:22:47","slug":"phantom-midge","status":"publish","type":"post","link":"https:\/\/uwm.edu\/field-station\/bug-of-the-week\/phantom-midge\/","title":{"rendered":"Phantom Midge (Family Chaoboridae)"},"content":{"rendered":"

Regards, BugFans,<\/p>\n

Phantom midge larvae orient horizontally in the water, turning slowly, rising and sinking in the water column, reminding the BugLady of a young pickerel she once knew.<\/p>\n

Phantom Midges<\/h3>\n

Phantom midges are not mosquitoes. They\u2019re flies (order Diptera), and in books, they\u2019re often lumped with mosquitoes (family Culicidae) and midges (family Chironomidae). All have aerial adults and aquatic young, and phantom midges (family Chaoboridae) resemble mosquitoes superficially, but, where it really counts\u2014in the mouthparts—vive la difference<\/em>! An adult phantom midge has a very short proboscis, and conventional wisdom holds that it does not\/cannot bite. One source conceded a little nectar feeding for some species, but because BugFans want to be on the cutting edge of entomological research, it should be noted that a 2010 publication suggests that the mouthparts (of an unspecified genus) are long enough for biting, a position strengthened by the incriminating presence of blood (of an unspecified genus) in some females\u2019 guts.<\/p>\n

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Adult PMs look translucent, but the name really comes from their transparent larva (sometimes called glassworms). An alternate explanation for \u201cphantom\u201d is that the markings on the larva\u2019s back resemble a ghostly face (the BugLady can\u2019t discern those hidden pictures either, no matter how hard she squints). This larva (which the BugLady scooped from an ephemeral pond) looks like it belongs in the genus Mochlonyx<\/em>, and the adult looks like Chaoborus punctipennis<\/em> (no, that is not what that means. Settle down.). The BugLady did a little dictionary work and Merriam-Webster<\/em> gave up the following: Puncti<\/em> comes from the Latin for point or marked with minute spots\/dots\/points.\u201d Penne comes from penna<\/em>, the Italian word for quill, which comes from the Latin word for feather (pinna) or wing (penna). \u201cWings with tiny spots?\u201d Try Bugguide<\/a>\u00a0for a glamour shot of the adult. The male\u2019s ultra-feathery antennae help him detect females, and his long abdomen ends with claspers.<\/p>\n

Because PM larvae live in glass houses, we can see what\u2019s going on inside, and the first thing we notice is a pair of pigmented blobs in front and another in the rear (kind of counter-productive, camouflage-wise, to carry dark baggage inside a crystalline container). These extensions of the tracheal tubes are not lungs but are hydrostatic organs (swim bladders) that allow a PM larva to maintain its position in the water column effortlessly. The larva breathes through its body surface, but its swim bladders may allow it to extend its stay in the low-oxygen conditions on a pond\u2019s floor. The BugLady was unable to find an anatomical diagram of a PM larva that labeled anything beyond the swim bladders, but it looks like there are some circulatory and nerve structures in there, too.<\/p>\n

PM larvae have prehensile antennae that are modified to grasp their prey\u2014daphnia, rotifers, small mosquito larvae, and other PM larvae\u2014crush it, and deliver it to their mouth. They may also do a little filter feeding. Apparently, fish aren\u2019t fooled by transparency, and PM larvae are a favored fish food (fly-tiers can find instructions for tying a lure of a PM larva). They are consumed by other aquatic predators and by birds. To avoid being eaten, and to follow the movements of their equally planktonic food supply, the larvae of many species of PMs migrate daily from the sediments at a pool\u2019s bottom to the open water near the surface as the sun sets, and back to the bottom when it rises. Migratory inclinations wax and wane depending on the age\/stage of the PM larva, but development of the hide-during-the-day-and-feed-at-night behavior seems to depend on whether the species evolved in fishy waters.<\/p>\n

Larval lifestyles seem to be fairly similar across the board. Eggs that are laid in gelatinous rafts at the water\u2019s surface hatch in a week or so, and the larval stage lasts for six to eight weeks. Both the larvae and pupae are ambulatory, moving by wriggling (the pupae are vertical migrators, too). See a picture of a PM pupa<\/a>. Here in the North Country, there\u2019s a single generation per year, which overwinters as mature larvae. When it\u2019s time to emerge as an adult, the floating pupa splits the back of its thorax and the adult climbs out directly into the air, by-passing the clingy surface tension. Adult phantom midges live only a few days, sometimes spending those days in the company of thousands of their confreres in what are described as \u201csmoke-like plumes.\u201d<\/p>\n

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They\u2019re everywhere. PM larvae are found, sometimes very abundantly, in still, open waters around the globe, where their ability to live in low-oxygen conditions allows them to be tolerant of water pollution. One study in a Dutch lake found 1,400 to 1,800 individuals per square meter, with an annual biomass of more than 10 pounds of one species of PM alone. Not surprisingly, they\u2019ve been known to clog water filtration systems. In another European study, PM larvae were thick enough in the water that their movements could be tracked with sonar. When a population of these tiny predators is that dense, it can shape the make-up of the rest of the community.<\/p>\n

Culled from the Phantom Midge Larvae literature:<\/p>\n