**3.5 Non-biting midges in proglacial ponds**

Non-biting midges are first colonizers of ephemeral ponds in the proximity of glacier snout. The appearance of new ponds is usually followed by their rapid disappearance and by a concomitant appearance of new ones, frequently observed in the Alps above the tree line [47]. Most of them are relatively small (surface <2 ha) [48], unproductive due to their sparse soil development and small catchments. Ponds are especially susceptible to the effects of climatic changes because of their relatively low water volumes and high surface area-to-depth ratios. Therefore, they act as early indicators of the impacts of climate change. During the ice-free months, typically, they undergo high-level fluctuations due to ice-snow melt rate and rainfall pattern. In winter, they freeze, totally if shallow [48]. Water temperature can be highly variable as well, ranging from 0 to 15°C during summer.

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**Figure 5.**

*Glacial Biodiversity: Lessons from Ground-dwelling and Aquatic Insects*

might be found with high density, up to >1000 individuals/m<sup>2</sup>

The zoobenthic community of Alpine proglacial ponds is dominated by chironomid Orthocladiinae (generally representing >70% of the community) followed by Diamesinae (*Pseudokiefferiella parva* and *Diamesa* spp.). Aquatic beetles (e.g., Elmidae, Dytiscidae and Hydrophilidae), Oligochaeta (e.g., Enchytraeidae) and Hydracarina frequently represent the remaining fauna. Overall, the richness is low, with few dozens of species colonizing the same pond. Few taxa

and less than 2 m deep. Among orthoclads, semiterrestrial genera are frequent (e.g., *Metriocnemus*, *Smittia* and *Parasmittia*), being environments that undergo high water level fluctuations during the ice-free period [49] (**Figure 5**). There are evidence of colonization by up to 4–5 congeneric species of *Metriocnemus* in

*Catching* Metriocnemus *adults (non-biting midges) with tweezers on the shoreline of the Agola proglacial pond (2596 m a.s.l., 46°N, 10°E, Brenta Dolomites Mts., Italian Alps) (photo by D. Debiasi/archive MUSE).*

in ponds >2 ha

*DOI: http://dx.doi.org/10.5772/intechopen.92826*

*Glacial Biodiversity: Lessons from Ground-dwelling and Aquatic Insects DOI: http://dx.doi.org/10.5772/intechopen.92826*

*Glaciers and the Polar Environment*

low temperatures during summer.

**3.4 Non-biting midges on the glacier**

**3.5 Non-biting midges in proglacial ponds**

surrounding landforms (e.g., scree slopes) in terms of temperature regime and depth of the substrate. Active rock glaciers show occurrences of cold-adapted species. Even though ground beetle communities of active rock glaciers show few differences in terms of species richness and abundance with respect to scree slopes, some characteristic species of each of the two landforms can be identified. The ground beetle community observed on the rock glaciers is exclusive of this landform because it is composed of large populations of species belonging to the genera *Oreonebria*, *Nebria* and *Trechus* [16, 40]. To these genera belong species (e.g., *Nebria germari*, *Oreonebria soror* and *Trechus tristiculus*) typical of cold and wet highaltitude environments. These species have two kinds of life style: epigeic (they move on the surface of the rock glacier where the rocky detritus is fine) and endogeic (they reach the depth of the stony detritus moving between the interstitial space between stones). Conversely, the surrounding ice-free landforms (e.g., scree slopes) host species assemblages characterized by the presence of species typical of alpine grasslands (e.g., *Carabus* spp. and *Cymindis vaporariorum*). Therefore, an active rock glacier can be defined as a superficial subterranean habitat [16] represented by

fissure network among boulders, human-sized caves included.

Unlike other superficial subterranean habitats like scree slopes, where temperatures could reach relatively high values in summer [16, 42], rock glaciers are selected by cold-adapted species, which avoid scree slopes as they do not offer constantly

To our knowledge, the only aquatic insects found permanently colonizing the ice are non-biting midges of the genus *Diamesa* in temperate zones and the stonefly *Andiperla willinki* (family Gripopterygiidae) in South America [43]. Larvae of *Diamesa steinboecki* and *Diamesa latitarsis* were collected on one Alpine glacier (2625–2650 m a.s.l., Agola, Brenta Dolomites, Italy), surviving a summer temperature ranging for 0.07 to 0.19°C. Larvae of *Diamesa* were collected also on Yala glacier (5100–5700 m a.s.l., Nepal, Himalayas [44, 45]), growing in melt-water drainage channels under the ice and feeding on blue-green algae and bacteria. They eat the scares allochthonous detritus transported by the wind and left by the glacier in the ice melt waters. Typically, primary food resources in eukryal consist of dust (allochthonous particles or airborne detritus) and algae (various species of cyanophytes and green algae), and fungi and bacteria associated with algae and detritus [46]. Adults were brachypterous (characterized by reduced wings), unable to fly, walking at temperatures as low as −16°C on the surface of the glacier and in small

Non-biting midges are first colonizers of ephemeral ponds in the proximity of glacier snout. The appearance of new ponds is usually followed by their rapid disappearance and by a concomitant appearance of new ones, frequently observed in the Alps above the tree line [47]. Most of them are relatively small (surface <2 ha) [48], unproductive due to their sparse soil development and small catchments. Ponds are especially susceptible to the effects of climatic changes because of their relatively low water volumes and high surface area-to-depth ratios. Therefore, they act as early indicators of the impacts of climate change. During the ice-free months, typically, they undergo high-level fluctuations due to ice-snow melt rate and rainfall pattern. In winter, they freeze, totally if shallow [48]. Water temperature can be

highly variable as well, ranging from 0 to 15°C during summer.

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cavities beneath it.

The zoobenthic community of Alpine proglacial ponds is dominated by chironomid Orthocladiinae (generally representing >70% of the community) followed by Diamesinae (*Pseudokiefferiella parva* and *Diamesa* spp.). Aquatic beetles (e.g., Elmidae, Dytiscidae and Hydrophilidae), Oligochaeta (e.g., Enchytraeidae) and Hydracarina frequently represent the remaining fauna. Overall, the richness is low, with few dozens of species colonizing the same pond. Few taxa might be found with high density, up to >1000 individuals/m<sup>2</sup> in ponds >2 ha and less than 2 m deep. Among orthoclads, semiterrestrial genera are frequent (e.g., *Metriocnemus*, *Smittia* and *Parasmittia*), being environments that undergo high water level fluctuations during the ice-free period [49] (**Figure 5**). There are evidence of colonization by up to 4–5 congeneric species of *Metriocnemus* in

#### **Figure 5.**

*Catching* Metriocnemus *adults (non-biting midges) with tweezers on the shoreline of the Agola proglacial pond (2596 m a.s.l., 46°N, 10°E, Brenta Dolomites Mts., Italian Alps) (photo by D. Debiasi/archive MUSE).* single Alpine ponds (Agola glacier, 2596 m a.s.l., Brenta Dolomites, Italy), with *M. fuscipes* and *M. eurynotus* as dominant species. The genus is considered semiterrestrial, found in mosses, phytotelmata, springs, ditches, streams and occasionally in the middle of lakes and rock pools [50]. Some ability to survive desiccation and hibernation often in combination with cocoon building and migration of larvae into the sediment [51] has been recorded for several *Metriocnemus* species dwelling in ephemeral habitats that seasonally dry or freeze out. The colonization of these ponds by *Metriocnemus* might be due more to these physiological adaptations than to repeated recolonization as observed for other chironomids colonizing ephemeral ponds [52]. In fact, due to the high geographical isolation of the pond and scarce connectivity with other suitable habitats in the catchment, we can suppose that these species persist by activating a physiological response to physical stress. Most of these species are univoltine, entering diapause in a desiccated-frozen state until spring thawing.
