Entomology Department

 Halobates - Oceanic Insects

Illustrated key to the sea skaters, Halobates, and allied genera

Nils Møller Andersen
Zoological Museum, University of Copenhagen

Ó Copyright, N. M. Andersen & Zoological Museum, University of Copenhagen

INDEX

Introduction

Asclepios

Halobates

Halobates
(Hilliella)

Halobates
(Halobates)

Oceanic Halobates

Halobates micans gr.

Coastal Halobates

Halobates fijiensis gr.

Halobates
princeps


Halobates
alluaudi
gr.

Halobates
matsumurai
gr.

Halobates
formidabilis

Halobates
proavus
gr.

Halobates
sexualis
gr.

Halobates
hayanus
gr.

Halobates
poseidon
gr.

Halobates
flaviventris
gr.

Halobates japonicus gr.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Introduction

The following key should enable the user to identify most specimens of Halobates and allied genera. The key generally works best for adult males, where the structures of the abdominal end usually provides good diagnostic characters. Adult females are usually much more difficult to identify. The terminology used in the keys is explained above.

 

1. Halobates and allied genera (tribe Halobatini)

Dorsal surface of body with extensive pale markings on head, thorax, and abdominal dorsum (as Austrobates rivularis)

Dorsal surface of body chiefly dark, pale markings usually limited to head and pronotum

Segment 8 of male (s8, t8) elongate, longer than wide, without spiracular processes; ventral styliform processes (st) short and stout, almost parallel

Segment 8 (s8) of male broad, wider than long, with spiracular processes; ventral styliform processes (st) long and slender, often diverging

Mangrove swamps
South and East Asia

Freshwater streams
Northeastern Australia

Various marine habitats
Widespread

Asclepios

Austrobates rivularis

Halobates

Go to 2

 

Go to 3

 

2. Asclepios

 

(under construction)

 

3. Halobates

Fore tarsal segment I, 0.3x or less longer than segment II
Middle femur at most 1.05x longer than hind femur

Fore tarsal segment I, more than 0.3x longer than segment II
Middle femur 1.1x or more longer than hind femur

Brown and yellow species usually with posterior margin of pronotum, most of thoracic pleura, and prominent stripes on femora, yellow

Dark brown to black species with most of thoracic pleura dark and only bases of anterior femora, yellow

Apices of male styliform processes slender and curved (as in Halobates mjobergi)

Apices of male styliform processes slender and straight (H. zephyrus)

Apices of male styliform processes variable in shape (as in H. darwini)

Northern Australia, New Guinea

Eastern Australia

Widespread

Halobates (Hilliella)

Halobates (s.str.) zephyrus

Other Halobates (s.str.)

Go to 4

 

Go to 5

  

4. Halobates, subgenus Hilliella

 

Fore femur of male depressed ventrally in distal fourth with an elongate patch of stiff hairs
Male proctiger widest across middle; apices of styliform processes simple
Length 3.3-3.8 mm (male), 3.4-4.2 mm (female)

Fore femur of male not modified ventrally, more or less tapering in width toward apex
Male proctiger widest in basal third
Slightly larger species, length 3.6-4.5 mm (male), 4.3-4.7 mm (female)

Male proctiger distinctly produced laterally in basal third; apices of styliform processes slightly widened, pointed
Thorax and abdomen above chiefly dark brown

Male proctiger widened but not distinctly produced laterally in basal third; apices of styliform processes simple
Thorax and abdomen above chiefly brown or yellowish brown

Female meso-metanotum without dark bristles

Female meso-metanotum without dark bristles

Female meso-metanotum with scattered, long dark bristles

Northern Australia, New Guinea

Northern Territory, Western Australia

Western Australia

Halobates (Hilliella) mjobergi

Halobates (Hilliella) lannae

Halobates (Hilliella) robinsoni

  

5. Halobates, subgenus Halobates

 

Yellow marks on dorsal head surface limited to a pair of oval marks at the base (as in Halobates germanus)
Interocular width of head subequal to or more than 3.6x width of an eye

Yellow marks on dorsal head surface more extensive, either with a crescent-shaped mark at base (as in Halobates hayanus) or with prominent yellow stripes along eyes (as in H. zephyrus)
Interocular width of head less than 3.6x width of an eye

Body including thoracic and abdominal venter, uniformly dark

Conspicuous yellow or brown markings on some parts of venter

On ocean surface

In various coastal marine habitats

Oceanic Halobates (s.str.) species

Coastal Halobates (s.str.) species

Go to 6

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6. Oceanic Halobates (s.str.) species

 

Large species, 4.0 mm or more (females) or 4.4 mm or more (males)

Small species, less than 3.8 mm (females) or less than 4.0 mm (males)

 

Antennal segment I much more than 0.5x as long as segment IV
Fore tarsal segment I about 0.6x longer than segment II
Male abdominal end as illustrated

Antennal segment I 0.5x as long as segment IV
Fore tarsal segment I about 0.4x longer than segment II
Male abdominal end as illustrated

All oceans

Indian and Pacific Oceans

Pacific Ocean

Halobates (s.str.) micans group

Halobates (s.str.) germanus

Halobates (s.str.) sericeus

Go to 7

 

 

 

7. Halobates (s.str.) micans group

   

Hind femur long, more than 0.8x as long as middle femur and at least twice as long as hind tibia

Hind femur short, less than 0.8x as long as middle femur and not twice as long as hind tibia

Male proctiger relatively short and broad, finger-like produced laterally

Male proctiger as broad as long, laterally produced but not finger-like

 

Fore tarsal segment I subequal to or slightly longer than segment II
Left styliform process of male bowed outward, not right angled

Fore tarsal segment I shorter than segment II
Left styliform process of male bent abruptly upwards at a right angle

Eastern Pacific Ocean

Eastern Pacific Ocean

All oceans

Halobates (s.str.) sobrinus

Halobates (s.str.) splendens

Halobates (s.str.) micans

 

8. Coastal Halobates (s.str.) species

Fore tarsal segment I subequal to or longer than segment II Large species, length 5.8 mm or more

Fore tarsal segment I shorter than segment II
Small species, length less than 5.8 mm

Male abdominal segment 8 enclosed within the enlarged, tubular segment 8
Right styliform process very short and deformed

Male abdominal segment 8 clearly visible, never enclosed within a tubular segment 8
Right styliform process may be short, but not deformed

 

Western Pacific Ocean

Indo-Pacific

Halobates (s.str.) fijiensis group

Large Halobates (s.str.) species

Small Halobates (s.str.) species

Go to 9

Go to 10

Go to 14

 

9. Halobates (s.str.) fijiensis group

 

Male proctiger almost parallel-sided

Male proctiger more or less shield-shaped, sides not parallel

Female connexiva forming two large triangles
No black bristles on anterior margin of meso-metanotum

Female connexiva not modified
No black bristles  on anterior margin of meso-metanotum

Female connexiva not modified
Stout black bristles present on anterior margin of meso-metanotum

 

Right styliform process of male decurved at apex, reflexed at base and visible from above
Female very broad posteriorly, width of body through hind coxae wider than head through eyes

Right styliform process of male flattened, its apex lanceolate, not visible from above
Female only as broad through hind coxae as width of head through eyes

Tonga

New Caledonia, Vanuatu

Fiji

Halobates (s.str.) salotae

Halobates (s.str.) katherinae

Halobates (s.str.) fijiensis

 

10. Large Halobates (s.str.) species

 

Right styliform process of male segment 8 much shorter than left process and directed outward

Right styliform process of male segment 8 similar to left process, not directed outward

 

Male proctiger broadly expanded laterally, with sub-parallel sides

Male proctiger at most narrowly expanded laterally, usually protruding but never parallel-sided

Micronesia

Indo-Pacific

Halobates (s.str.) mariannarum

Halobates (s.str.) kelleni, princeps, etc.

Other large Halobates (s.str.) species

 

Go to 11

Go to 13

 

11. Halobates (s.str.) kelleni, princeps, etc.

 

Male fore femur with a tubercle beneath. A large species, over 6 mm

Male fore femur not modified.                                                Smaller species, length not over 5.8 mm

Male proctiger with two pointed prominences on each side

Male proctiger with one pointed prominence on each side

Male proctiger with postero-lateral angles rounded

Indo-Australian

Andaman Sea, India

Halobates (s.str.) princeps

Halobates (s.str.) kelleni,  and alluaudi group

Halobates (s.str.) elephanta

 

Go to 12

 

 

12. Halobates (s.str.) kelleni and alluaudi group

Proctiger much longer than broad, anterolateral angles angulate.                         Length 4.5 mm (male)

Proctiger about as broad as long, anterolateral angles rounded.                                      Length 5.0-5.8  mm (male)

 

Apices of male styliform processes tapering in width

Apices of male styliform processes blunt

Female thorax in side view strongly arched

Female thorax not modified

Samoa

East Africa, Madagascar, Seychelles

Mauritius

Halobates (s.str.) kelleni

Halobates (s.str.) alluaudi

Halobates (s.str.) tethys

 

13. Halobates (s.str.) matsumurai group

 

Smaller species, length of male less than 6 mm

Larger species, length of male 6 mm or more

 

Male body oval, much wider at the bases of legs than at anterior margin of meso-notum

Male body cylindrical, parallel-sided, hardly, if at all, wider at the bases of middle and hind legs than at anterior margin of meso-notum

Palau Is., New Guinea

China, Japan, Korea, Taiwan

Indo-Australian

Halobates (s.str.) nereis

Halobates (s.str.) matsumurai

Halobates (s.str.) browni, esakii

 

14. Halobates (s.str.) formidabilis, etc.

   

Fore femur of male strongly incrassate, fore tibia with a long spinous process on inner margin
Male pronotum distinctly swollen
Inner margin of fore tibia of female sinuate

Fore femur and tibia of male not modified
Male pronotum not distinctly swollen
Inner margin of fore tibia of female straight

 

Fore tarsal segment I, 0.6x or less length of segment II

Fore tarsal segment I, more than 0.6x length of segment II

Andaman Sea, India, Sri Lanka

Indo-Pacific

Halobates (s.str.) formidabilis 

Halobates (s.str.) proavus group

Other Halobates (s.str.) species

 

Go to 15

Go to 23

 

15. Halobates (s.str.) proavus group

   

Male proctiger subtriangular
Fore tarsal segment I, 0.3x (male) or 0.4x (female) as long as segment II

Male proctiger more or less pentagonate
Fore tarsal segment I, more than 0.3x (male) or 0.4x (female) as long as segment II

Males with black bristles along sides of meso-metanotum
Male styliform processes slender

Males without black bristles along sides of meso-metanotum
Male styliform processes stoter, left one strongly curved

 

Female thorax with a mid-dorsal, longitudinal groove and an orange stripe

Female thorax without groove and orange stripe

 

Indo-Malayan

Indo-Pacific

Halobates (s.str.) proavus

Halobates (s.str.) maculatus

Other small Halobates (s.str.) species

 

 

Go to 16

 

16. Other small Halobates (s.str.) species

Apices of styliform processes of male boot-shaped

Apices of styliform processes of male variable in shape, but never boot-shaped

 

Both male and female completely yellow beneath

Male not completely yellow beneath, thoracic venter darkened

Indo-Australian

Australian

Indo-Pacific

Halobates (s.str.) sexualis group

Halobates (s.str.) regalis, whiteleggei 

Other small Halobates (s.str.) species

Go to 17

Go to 20

Go to 21

17. Halobates (s.str.) sexualis group

 

Male and female meso-metanotum with scattered dark bristles

Male and female meso-metanotum without dark bristles

Male proctiger almost symmetrical; lateral, right-hand finger-like projection not much longer than the left-hand projection (as in Halobates peronis and H. acherontis)

Male proctiger strongly asymmetrical; lateral, finger-like projections on right side very long

Indo-Australian

Australia, Southern New Guinea

Australia, Southern New Guinea

Halobates (s.str.) dianaemurphyi, peronis, sexualis 

Halobates (s.str.) acherontis, darwini 

Halobates (s.str.) herringi

Go to 18

Go to 19

 

 

18. Halobates (s.str.) murphyi, peronis, sexualis

   

Apices of styliform processes almost symmetrical, only slightly widened

Apices of styliform processes asymmetrical, distinctly widened

 

A small species, length 3.9 mm (males and females)

A large species, length 4.5 mm (males), 4.6 mm (females)

West Malaysia, Sri Lanka

Bismarck Arch., Philippines, Solomon Is.

Northern New Guinea

Halobates (s.str.) sexualis

Halobates (s.str.) dianae, peronis

Halobates (s.str.) murphyi

 

19. Halobates (s.str.) acherontis, darwini

Body length 4.5-4.8 mm (male) or 4.3-4.8 mm (female)

Body length 3.8-4.2 mm (male) or 3.8-3.9 mm (female)

 

Meso-metanotum with few short dark bristles

Meso-metanotum with numerous long dark bristles

 

In mangroves
Australia, Southern New Guinea

In rivers
Western Australia

Halobates (s.str.) darwini

Halobates (s.str.) acherontis

 

 

20. Halobates (s.str.) regalis, whiteleggei

Fore tarsal segment I, 0.5x (male) or 0.6x (female) length of segment II. Male terminalia as illustrated

Fore tarsal segment I, 0.4x (male) or 0.5x (female) length of segment II. Male terminalia as illustrated

 

Hind coxae of female shorter, only about 2.0x as long as wide

Hind coxae of female very long, about 3.0x times as long as wide

 

Australian

Eastern Australian

 

Halobates (s.str.) regalis

Halobates(s.str.) whiteleggei

 

21. Halobates (s.str.) hayanus group, etc.

       

Male and female with scattered black bristles on meso-metanotum. Male terminalia as illustrated

Male and female without scattered black bristles on meso-metanotum

 

Male proctiger with a distinct patch of black spine-like bristles on each side. Styliform processes almost symmetrical, their apices diverging

Male proctiger without a patch of black spine-like bristles or only a group of small spines. Styliform processes neither symmetrical nor diverging apically

 

Female more than 4.3 mm

Female 4.3 mm or smaller

Galapagos Is.

Indo-Australian

Indo-Pacific

Halobates (s.str.) robustus

Halobates (s.str.) calyptus, hayanus

Halobates (s.str.) bryani, and poseidon group

 

 

Go to 22

22. Halobates (s.str.) bryani and poseidon group

   

Left styliform process of male visible from above, both processes diverging posteriorly
Female without black bristles on hind acetabula

Left styliform process of male not visible from above, both processes converging posteriorly
Female with a group of stout black bristles on hind acetabula

A small brown species, 3.3-3.5 mm

Yellow colouration of head usually crescent-shaped, never reaching bases of antennae, occasionally with a yellow spot at bases of antennae

Yellow colouration of head extensive, extending uninterrupted to bases of antennae, leaving a lyre- or arrow-shaped spot in center

Fiji Is.

East Africa, Madagascar

Red Sea

Halobates (s.str.) bryani

Halobates (s.str.) poseidon

Halobates(s.str.) melleus

 

23. Other Halobates (s.str.) species

   

Left styliform process curved outward and visible from above

Left styliform process not curved outward and visible from above

 Female with yellow colouration of venter limited to abdominal segments and sometimes middle acetabula

Female with yellow colouration of venter more extensive, usually extending forward to bases of fore legs

Malayan

Indo-Pacific

Indo-Australian

Halobates (s.str.) trynae

Halobates(s.str.) flaviventris group

Halobates (s.str.) panope and japonicus group

 

Go to 24

Go to 25

 

24. Halobates (s.str.) flaviventris group

No dense, stiff black bristles on hind acetabula
Undersurface of middle acetabula with a wide yellow band
Male terminalia as illustrated

Dense, stiff black bristles on hind acetabula
Undersurface of middle acetabula without a wide yellow band
Male terminalia as illustrated

 

Hind coxae of female short and straight, never 1.5x as long as fore tarsal segment I

Hind coxae of female elongate and curved, at least 1.5x as long as fore tarsal segment I

 

Indo-Pacific

Central Pacific

 

Halobates (s.str.) flaviventris

Halobates (s.str.) hawaiiensis

 

 

25. Halobates (s.str.) panope and japonicus group

 

Right styliform process of male curved outward and visible from above; lateral edges of male proctiger rounded
Female with median triangular area on meso-metasternum, entire abdominal venter, and basal third of fore femora, yellow

Right styliform process of male neither curved outward nor visible from above; lateral edges of male proctiger angular
Yellow colouration of female venter more limited, basal parts of fore femora dark

 

A large species, 5.0-5.2 mm in length
Male terminalia as illustrated
Female without black bristles on meso-metanotum

A small species, much less than 5.0 mm in length
Male terminalia as illustrated
Female usually with black bristles on meso-metanotum

India, Sri Lanka

Japan

New Caledonia

Halobates (s.str.) galatea

Halobates (s.str.) japonicus

Halobates (s.str.) panope

 


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 Last update: 04 september 2002