Gyrinus aquiris was the most abundant (45.4%) and one of the most frequently collected gyrinid (6%) in this survey. The species was collected in every county of Prince Edward Island (Table 2).

In Prince Edward Island, G. aquiris was collected both from lotic (50%) and lentic (50%) environments (Tables 1–2), which is similar to the observations made by Alarie (2009) in the Magdalen Islands. Oygur and Wolfe (1991), however, reported 80% of specimens from lentic habitats whereas Morrissette (1979) reported the species from ponds and lakes invaded by aquatic plants.

Gyrinus aquiris was reported from the Magdalen Islands (Alarie 2009), and the Maritime Provinces of New Brunswick (Oygur and Wolfe 1991; Roughley 1991a; Webster 2016) and Nova Scotia (Campbell et al. 1987). Although Roughley (1991a) reported it from Prince Edward Island, Majka (2008) removed it from the province’s faunal list since there were no voucher specimens or published records.

This very small gyrinid was collected in relatively low number (five specimens) at four different localities of Kings and Prince Counties (Table 2).

Robert (1955) and Morrissette (1979) reported this species from small deep lakes near dense emergent vegetation (i.e., Carex and Scirpus spp.). Oygur and Wolfe (1991) reported it primarily (71%) from lentic habitats. The specimens collected in this survey were predominantly from lentic habitats (Tables 1–2).

Gyrinus latilimbus was reported from New Brunswick (Roughley 1991a; Webster 2016) and Nova Scotia (Roughley 1991a).

Eight specimens were collected from four different localities of Kings and Prince Counties (Table 2).

Robert (1955), Morrissette (1979) and Alarie (2009) reported Gyrinus pugionis from peaty or semi-peaty lakes; Robert (1955) mentioned that it invades narrow outflow streams from such lakes. Oygur and Wolfe (1991) reported it primarily (88%) from lentic habitats. In Prince Edward Island, most specimens were collected from lentic habitats (Tables 1–2).

This species was reported from the Provinces of New Brunswick (Roughley 1991a; Webster 2016) and Nova Scotia (Roughley 1991a), and from the Magdalen Islands (Alarie 2009).

Whereas found in relatively low numbers (5 specimens) Haliplus connexus is reported for in each of the three Prince Edward Island counties (Table 2).

In Atlantic Canada, there are records from small streams, eutrophic ponds, river margins, slow streams and temporary habitats (Majka et al. 2009). In Prince Edward Island, all specimens of Haliplus connexus were collected along the edge of weedy lentic habitats (Tables 1–2).

The species is known also from the neighboring Maritime Provinces of New Brunswick and Nova Scotia (Matheson 1912; Wallis 1933; Roughley 1991b).

This species is known from Prince Edward Island by a single specimen record from Prince County (Table 2).

These beetles occur in the emergent zone of sun-warmed permanent or semi-permanent ponds in forested area (Larson et al. 2000). In Prince Edward Island, A. sylvanus was collected in a permanent pond on clay bottom located at the edge of a spruce and aspen forest (Tables 1).

This species is known only from the neighboring Province of New Brunswick (Webster 2008). The presence of A. sylvanus in Prince Edward Island represents the easternmost record of this species in Canada.

This species is reported from four specimens collected in Kings (3) and Prince Counties (1) (Table 2).

Agabus bifarius occurs amongst emergent grasses and sedges at the margin of a variety of lentic habitats, but it is especially characteristic of the margins of shallow, exposed, vernal ponds (Larson et al. 2000), which is essentially the type of habitats where it was found in Prince Edward Island (Table 1).

This species is also known from New Brunswick and Nova Scotia (Larson et al. 2000).

Agabus erytropterus is reported from eight specimens collected at five localities of Kings County (Table 2).

This species is usually associated with slowly flowing water but occurs in depositional areas with thick organic silt (Larson et al. 2000), which is exactly the type of habitats where it was found in Prince Edward Island (Table 1).

Agabus erytropterus is also known from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Agabus punctulatus is reported from nine specimens collected at one locality in Prince County (Table 2).

The most typical habitat of this species is flooded grass along the margin of vernal ponds in open grassland areas (Larson et al. 2000), which is similar to the habitat where A. punctulatus was found in Prince Edward Island (Table 1).

This species is known also from the neighboring Maritime Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Agabus semipunctatus is reported from nine specimens from six localities of Kings and Prince Counties (Table 2).

Agabus semipunctatus most often occurs in Sphagnum bogs but can also be collected regularly from Carex-choked waters (Larson et al. 2000). In Prince Edward Island, this species was essentially found in similar type of habitats (Table 1).

This species is also known from the neighboring Maritime Provinces of New Brunswick and Nova Scotia (Larson et al. 2000) and the Magdalen Islands (Alarie 2009).

Colymbetes paykulli is reported from two specimens each collected in Queens and Kings Counties (Table 2).

These beetles are almost entirely restricted to the cold water of Sphagnum bogs. They occur most frequently in small pools with emergent Carex, or along the edges of bog-ring lakes in embayments and beaver runs, often or near the willow zone (Larson et al. 2000). The two specimens collected in Prince Edward Island were from a Sphagnum bog and a shallow pool covered with vegetation respectively (Table 1).

This species is known also from the neighboring Maritime Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Graphoderus liberus is reported from two specimens collected in Prince County (Table 2).

These beetles generally occur in boggy (often brown water) ponds and lakes. They are usually found at the edge of the encircling bog in embayments or beaver runs (Larson et al. 2000). The two specimens collected in Prince Edward Island were from Sphagnum bog ponds (Table 1).

This species is known also from the neighboring Maritime Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

This species is reported from several specimens collected at various localities in each county of the province (Table 2).

These beetles occur among moss or dense emergent vegetation and debris along the margins of small pools, ponds and springs. They occur in peatland as well as in sites where the water surface is shaded and the water is cool (Larson et al. 2000). Specimens were collected in Prince Edward Island from a variety of lentic and lotic habitats (Table 1).

This species is known also from the neighboring Maritime Provinces of New Brunswick and Nova Scotia (Larson et al. 2000), and the Magdalen Islands (Alarie 2009).

This species is reported from several specimens collected at several localities of Prince and Kings Counties (Table 2).

These beetles occur among dense emergent vegetation along the margins of small, often temporary pools, usually situated in grasslands, cleared areas or at the edges of forest, but not typically in forest pools. Hydroporus fuscipennis is usually found in more or less eutrophic pools and is not common in peatlands (Larson et al. 2000). Specimens were collected in Prince Edward Island essentially from cattail ponds and roadside ditches (Table 1).

This species is known also from the neighboring Maritime Provinces of New Brunswick (Larson et al. 2000).

This species is reported from several specimens collected in Prince and Kings Counties (Table 2).

In Newfoundland, this species has been collected from flooded grasses and emergent Carex along the margins of beaver ponds and roadside ponds. Specimens, which occurred on peaty substrates near boggy areas, were collected from areas exposed to the sun as well as from shorelines shaded by overhanging alder. In Prince Edward Island, H. goosei was collected in similar habitats, in addition to Sphagnum bogs and eutrophic creeks (Table 1).

This large, distinctive Hydroporus Clairville species has generally been confused with H. rectus Fall. In the Maritime ecozone, H. gossei is also reported from the neighboring Province of New Brunswick (Larson et al. 2000).

This species is reported from 16 specimens collected at two localities of Prince and Kings Counties (Table 2).

This species occurs in very small peatland pools, as well as in the moss mat along the margins of larger peatland pools and ponds (Larson et al. 2000). Specimens collected in Prince Edward Island were from a Sphagnum bog and the grassy shoreline of a pond (Table 1).

This species is known also from the neighboring Maritime Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Hydroporus striola was one of the most abundant (4.25%) and most common species collected in the province (Table 2).

Hydroporus striola occurs in almost all types of small, standing water where emergent vegetation is dense. Specimens occur in peatland pools, being most common in fen habitat and rather infrequent in ombrotrophic bog pools (Larson et al. 2000). Specimens collected in Prince Edward Island were from an array of lentic habitats as described above (Table 1).

Hydroporus striola is the most ubiquitous species of Hydroporus in the boreal zone of the North Temperate Region (Larson et al. 2000). In the Maritime ecozone, this species is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000), and the Magdalen Islands (Alarie 2009).

Several specimens of Hydroporus tenebrosus were collected in each of the three counties of Prince Edward Island (Table 2).

This species occurs mainly in forested regions but is also common in the prairie parkland. Beetles occur in the emergent zone of small, usually temporary pools and ponds. They are usually found in eutrophic, sun-warmed sites (Larson et al. 2000). In Prince Edward Island, H. tenebrosus was almost essentially collected only in ponds, ephemeral pools, and roadside ditches (Table 1).

The species is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000), and the Magdalen Islands (Alarie 2009).

Several specimens of Hydroporus tristis were collected from Kings and Prince Counties (Table 2).

This species occurs in a variety of lentic habitats. Specimens are usually found among dense emergent vegetation at the margin of small, often more or less shaded pools. Hydroporus tristis is also common in small peatland pools (Larson et al. 2000). Whereas collected in few eutrophic creeks in Prince Edward Island, H. tristis was most generally found in ponds and shallow pools characterized by heavy accumulation of organic debris as well as in Sphagnum bogs (Table 1).

The species is known also from the neighboring Province of New Brunswick (Larson et al. 2000), and the Magdalen Islands (Alarie 2009).

Hygrotus compar is reported from six specimens collected Prince County (Table 2).

In the Prairies, H. compar has been recorded from the margin of temporary ponds, usually in fresh water but specimens have also been found in saline ponds (Larson et al. 2000). In Prince Edward Island, specimens were found in a roadside ditch and a clay bed pond at the edge of a spruce and aspen forest (Table 1).

The species is known also from the neighboring Province of New Brunswick (Larson et al. 2000).

Hygrotus laccophilinus is reported from 22 specimens collected throughout the province (Table 2).

This species has been collected from a variety of small ponds. It appears to be most common among emergent grasses and sedges along the margin of permanent, or at least long lasting ponds. Specimens have been found most frequently in ponds in open country cleared of forest but they have also been collected in woodland ponds, especially beaver ponds (Larson et al. 2000). In Prince Edward Island, specimens were most frequently found in ponds and roadside ditches (Table 1).

The species is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Although found in relatively low numbers (seven specimens), this species is reported from each of the three Prince Edward Island counties (Table 2).

Ilybius discedens is one of the most characteristic water beetle species of boreal peatland generally occurring in small, moss-ringed pools, often where the water is cold to the touch (Larson et al. 2000). In Prince Edward Island, the majority of specimens were collected from Sphagnum bogs, although a few specimens were associated with eutrophic lotic habitats (Table 1).

This species is also known from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000), and the Magdalen Islands (Alarie 2009).

This species is reported from three localities of Prince County (Table 2).

This is a species of forested regions where it occurs amongst dense vegetation, usually Carex, at the margins of both temporary and permanent ponds (Larson et al. 2000). Except for one specimen, which was collected in a shallow creek, all specimens of Ilybius erichsoni were collected in the type of habitats mentioned by Larson et al. (2000) (Table 1).

This species is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000), and the Magdalen Islands (Alarie 2009).

This species is reported from five localities of Queens and Kings Counties (Table 2).

Specimens of Ilybius larsoni have generally been collected from small, cold woodland pools, usually with moss and accumulation of plant debris such as grass or sedge stalks or fallen leaves. Specimens have also been collected from small, peat-rich springs (Larson et al. 2000). In Prince Edward Island, this species was found in Sphagnum bogs and eutrophic creek (Table 1).

This species is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Laccornis latens is reported from two specimens collected in Kings County (Table 2).

The most common habitat for this species is semi-permanent, cool, shaded pools with deep leaf debris but few vascular plants; moss is often abundant (Larson et al. 2000). In Prince Edward Island, the two specimens sampled were collected within shoreline moss in a fen densely covered with Scirpus (Table 1).

This species is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Neoporus carolinus is reported from several specimens collected in Prince and Queens Counties (Table 2).

This species occurs among emergent vegetation such as sedges (Larson et al. 2000). In Prince Edward Island, beetles were collected from both lotic and lentic habitats, most of which characterized by dark brown water (Table 1).

Neoporus carolinus is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Neoporus clypealis is reported from 22 specimens collected in each of the three Prince Edward Island counties (Table 2).

This species occurs among emergent vegetation such as sedges, along the margins of slow, marshy streams, beaver ponds, and small lakes. Beetles are generally found where there is some water movement and are usually on mineral substrates (Larson et al. 2000). With few exceptions, most specimens collected in Prince Edward Island were from creeks and small rivers (Table 1).

Neoporus clypealis is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

Several specimens of Neoporus sulcipennis were collected at two localities of Prince County (Table 2).

This species occurs in small to medium sized warm, clear streams, often in depositional areas along the stream margins (Larson et al. 2000). In Prince Edward Island, all specimens were collected along the margins of rivers (Table 1).

Neoporus sulcipennis is known also from the neighboring Province of New Brunswick (Larson et al. 2000). The presence of this species in Prince Edward Island represents the easternmost record in Canada.

Rhantus consimillis is reported from five specimens collected at the same locality of Prince County (Table 2).

This species occurs in warm, weedy ponds, generally in open grassland areas. It has been collected from both permanent and temporary habitats (Larson et al. 2000). The specimens collected in Prince Edward Island were from a permanent pond located at the edge of a spruce and willow forest (Table 1).

Prior to this study, R. consimilis had only been reported in New Brunswick (Webster 2008). The presence of this species in Prince Edward Island is its easternmost report in Canada.

Five specimens of R. sinuatus were collected at two localities of Kings County (Table 2).

This species occurs in lentic habitats densely overgrown with emergent vegetation. The species is common in bogs, but it also occurs in habitats with dense sedges, rushes or Typha (Larson et al. 2000). In Prince Edward Island, specimens were collected from a permanent pond with Nymphaea and a Sphagnum bog (Table 1).

Rhantus sinuatus is known also from the neighboring Provinces of New Brunswick and Nova Scotia (Larson et al. 2000).

One specimen of R. suturellus was collected in Kings County (Table 2).

These beetles occur in cold, densely shaded water in forested areas, frequently found in bogs and fens (Larson et al. 2000). In Prince Edward Island, the specimen collected was found in a Carex pool with black sediments in a spruce forest (Table 1).

Rhantus suturellus is known also from the neighboring Provinces of New Brunswick (Webster 2008) and Nova Scotia (Larson et al. 2000) and the Magdalen Islands (Alarie 2009).

One specimen of S. pseudovilis was collected in Prince County (Table 2).

The species is very common in cold stenothermal springs where it can be taken either in the limnocrene pools or among the mosses along the spring margin (Larson et al. 2000). In Prince Edward Island, the only specimen collected was found in a narrow and shallow creek flowing on a sandy bed (Table 1).

This species is also known from the neighboring Province of New Brunswick (Webster 2008) and the Magdalen Islands (Alarie 2009).