Cheng, L.

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HALOBAWL!3 (HETEROPTERA : GERRIDAE) 
FROM THE SEAS AROUND NOSY BE, MAGALASY 
LANNA CHENG 
Scripps Insiitution of Oceanography 
Uniuersiiy of California, San Diego 
La Jollu, CA. 92037 
USA 
Trois espèces sont signalées : H. flaviventris, récoltée ù la lumière au-dessus du plateau continental et du talus; 
H. micans, capturée sur le plateau continental autour de !Yosy Ré, et dans l’Océan Indien entre le nord de Madagascar 
et l’équateur; I-I. germanus, capturée au large de ~VOS~ Bé, généralement non loin du talus. Presque toutes les captures 
ont lieu en saison sèche (mai-novembre). L’auteur distingue les stades de développement et les sexes. 
ABSTRACT 
Three species are noticed : II. flavivent.ris, collected in Iight-samples ut night on the continental shelf and slope; 
H. micans, collected on fhe shelf around :VOS~ Be, and in the lndian Ocean between north-Madagascar and equator ; 
H. germanus, collected off n’osy Re, generally net fur from the continental slope. Almost a11 are sampled in the rvet 
season (mai to november). Developmental stages and sex are identified. 
INTRODUCTION. 
The planktonic populations of the western Indian 
Ocean, particularly those of the Mozambique 
Channel, are almost completely unknown. Since 
one of the research stations of the Offic,e de la 
Recherche Scientifique et Technique Outre-Mer 
of the Republic, of France is located at Nosy Be, 
workers there are in a very convertient position to 
undertake studies on the plankton populations of 
that region. The first of their expeditions t.ook place 
in 1959, and since then several other &dies bave 
been carried ont. This paper deals with specimens 
of the oceanic insect Halobates collec,ted in 27 of the 
plankton tows taken at various times between 
1963 and 1972. 
MATERIAI, AN11 METHODS. 
About one-half of the samples were collected in 
the Nosy Re area and the other half from the Indian 
Oçean at t,he northern end of Madagascar Island. 
Thc year, stat.ion numbers, locat,ions, dates, and 
times of t,hese collections are givln in Table 1. 
Apart from three of the 1966 samples, which were 
caught by dip-netting animals attracted to lights 
at night,, a11 of the specimens were collected in 
plankton towa. The various types of gear used in 
the different tows are indicated by the third alphabet 
Cah. O.R.S.T.O.M., sér. OcÉanogr., vol. XII, no 2, 1974: 113-116. 
114 LANNA CHENG 
Year 
1963 
1965 
1966 
1967 
1968 
1969 
j- 
c._ 
::” 
Station No. 
NBV 88 
NBV 98 
NBH 463 
N-BH 465 
NBP 57 
Light 
Light 
Light 
NBL 1 
NBP 60 
NBP 61 
NBP 64 
NBP 71 
NBP 76 
NBC 594 
NBC 659 
NBC 783 
NBT 141 
NBT 173 
NBT 175 
NBT 176 
NBT 177 
NBT 178 
NBT 182 
NBT 183 
NBT 187 
NBT 188 
TABLE 1 
Number and species of Halobafes recorded for each station 
(g = germnnus, m = micans, f = flavivenfris) 
Location 
Longitude 0s Latitude OE 
12056’ 47050’ 
12056’ 48”lO’ 
13034’ 47044’ 
13027.5’ 48007’ 
13016’ 47025’ 
Continental shelf 
Nosy Mitsio 
Nosy Iranja 
13027’ 48007’ 
13033’ 47048’ 
14005’ 47026’ 
13054’ 47027’ 
12054’ 48009’ 
13018’ 47059.5’ 
13017’ 48044’ 
13019.5’ 48043.5’ 
13016’ 48037’ 
09043’ 50049’ 
08~09’ 50038’ 
07014’ 51004.5’ 
05043’ 51040’ 
05023’ 51048’ 
04012’ 52017’ 
07017’ 54020’ 
07043’ 54010’ 
12001’ 52028’ 
12050’ 51007.5’ 
.Tl41 
46 
I I I 
40” 50” 60’E 
- 00 
- IOT 
- 200 
- 300 
Fig. 1, - Collecting stations in the Indian Ocean and the 
northern end of Madagascar Island. ( l = H. micans, 
0 = H. germanus). 
Cnh. O.R.S.T.O.M., sér. Océanogr., vol. XII, no 2, 1974: 13-116. 
Depth 
tm). 
1940 
800 
1400 
48 
2800 
- 
- 
- 
48 
300 
1400 
2100 
500 
700 
16 
7 
14 
1600 
4000 
4500 
4750 
4700 
4400 
3900 
4000 
4200 
4100 
Date Hour Species 
22 Aug 
26 Sep 
19 Jul 
20 Jul 
3 Nov 
- Aug 
11 May 
16 Sep 
13 Apr 
7 Aug 
7 Aug 
8 Aug 
2 oct 
3 oct 
13 May 
28 May 
16 Jul 
28 Nov 
7 Apr 
8 Apr 
8 Apr 
9 Apr 
9 Apr 
13 Apr 
14 Apr 
15 Apr 
16 Apr 
0705 
0200 
2330 
0320 
0400 
- 
- 
- 
1300 
0445 
2130 
0900 
0000 
1800 
1355 
1810 
0950 
0235 
1900 
0450 
2100 
0410 
1840 
1935 
0030 
2330 
1930 
6 
B 
m 
m 
g 
f 
f 
f 
g 
g&m 
B 
g 
g 
g 
m 
m 
m 
m 
m 
m 
m 
m 
m 
m 
m 
m 
m 
Number of 
specimens 
3 
7 
6 
6 
2 
9 
2 
7 
42 
5 
2 
1 
1 
1 
1 
2 
2 
1 
2 
1 
4 
2 
2 
4 
1 
2 
1 
letter of the code preceding the station number (1). 
Descriptions and details on the operation of these 
nets - vertical - closing (( Discovery )) type (V), 
horizontal non-closing 0 Tregouboff )) type (H), and 
horizontal non-closing Q Larval Fish )) type (P) -- 
have been published by FRONTIER (1966), the 
« Clark-Bumpus » type net (C) was described by 
PETIT and BOUR (1971), and the (( Larval Tuna net )) 
(T) is a standard one-meter-diameter net with 
500 p mesh used by FAO and CalCOFI expeditions. 
RESULTS OF ANALYSIS. 
Al1 the specimens collected at light belong to 
Halobutes flaviventris Eschscholtz, an inshore species 
of the genus. Adults are rather large, dark grey 
insects, more than 4 mm in body lenght, distinguished 
from adult Halobates of the oceanic species by their 
relatively large eyes and by a characteristic pale 
yellow band on the ventral surface of the body 
(1) It should be notod that none of the tows wcre made 
specifically for collecting pelagic organisms, and since Halo 
bates only occur on the sea surface, they must have bcen 
caught when the net surfaced, hence the numbers of individuals 
caught (except NBL 1) were very low. 
(HERRING, 1961) : the venter of t,he oceanic species 
is uniformly pale brown. H. fluviventris has been 
recorded from various near-ehore localities of the 
Pacifie and Indian Oceans (HERRING, 1961), but 
this is the first time it has been found off the coaats 
of Madagascar. 
The remaining samples include both adults and 
nymphs of cither Halobates micans Eschscholtz or 
H. germanus White. One sample contains specimens 
of both species, which were likewise found associated 
in certain other sarnples collected in the Pacifie 
Ocean (CHENG, 1971, 1973 a). 
18 out of 24 samples were taken at night or the 
early morning hours belween 1800 and 0600 heurs. 
The much higher frequency of Halobates caught 
in night Lows is probably due Lo the evident ability 
of these insects 10 see an approaching net during 
daylight hours; since they cari move at a speed 
of 50-100 cm/sec, which is about the speed of most 
of the plankton tows, they presumably cari easily 
dodge the net and avoid being caught (CHENG, 
1973 b). 
The developmental stages of the specimens in 
each sample have also bcen identified as far as 
possible. Since Lhere were very few specimens in 
each sample collect.ed from the sarne general area, 
the nurnbers collected per month in the different 
years have been combined and the totals for each 
spec,ies frorn a11 the samples are presented in Table II 
TABLE II 
Xumher of different stages of Ilalohaies spccies collccted in differcnt rnonths (data pooled from different yoars) 
Specics Month Stages of Develonmcnl Number of 
If. flauiventris May 
Aug 
Sep 
If. germanrzs Apr 
AL& 
Sep 
Ckt 
Nov 
Il. micans Apr 
May 
JUI 
Aug 
Nov 
+ cast skin of insect 
1 II III 
- 
- - - 
- - 
1 1 
- 2” 
.- - - 
- - 
1 2 3 
- -._ 2 
1 7,1+ 
- - - 
- -_ -- 
II. flaviventris was collected at night in the months 
of May, August and September. Only adults were 
caught; this confirms our observation in t,he Pacifie 
Ocean that il is apparently only the adult Halobates 
which are attracted to lights (CHENG, in pess, A). 
H. germanus was collected in nine of the tows. 
As cari be seen in Table II, adult,s were found in 
a11 the rnonths, but nymphs were only found in 
the April and Au@ samplcs. (Two of the stages 
-- III and IV - were also represent.ed by cast 
skins.) More females (34j than males (22) were 
caught. 
More than half of the samples studied cont,ained 
H. micans; here, too, there were more females (8) 
than rnales (0). Nymphs of four of the five stages 
were collected in April and July, but none were 
found in the August and November satilples. A 
study of this species from Lhe Atlantic Ocean 
suggested that in the subtropical zones this insect 
probably reproduces without any distinct, seasonality 
(CHENG, 1973 c). 
., 
IV 
- 
2 
1 1. 
- 
1,3+ 
V 
- 
- 
- 
- 
1 
- 
- 
2,1+ 
- 
1 
- 
_ ._ 
6 
1 
3 
5 
18 
2 
1 
- 
1 
4 
-- 
1 
- 
i‘ 
1 
6 
2 
20 
a 
6 
n 0 
6 
1 
Collections 
Ten of Lhe samples collected from the Indian 
Ocean between 4” S and 1% S (fig. 1) contained 
inse&, a11 of them identified as H. micans, a cosmo- 
politan species widely diatributed in the Pacifie 
and Atlant,ic, as well as in the Indian Ocean (CHENG, 
1973 dj. Its known distribution in the Indian 
Ocean extends frorn 200 N to 200 S, and well into 
the Mozambique Channel down the toast of Africa 
to Lhe Atlantic Ocean. Several other samples frorn 
waters around ‘losy Bé (fig. 2) contained specimens 
of Lhis species, but are a11 nymphs except for one 
adult female. hdults of Lhis species are apparently 
seldom found in nearshore waters. 
Al1 the samples containing H. germanus were 
collected in the 1Mozambique Channel or in areas 
around Nosy Bé (fig. 1 and 2). This species, known 
only from Lhe Pacifie and Indian Oceans, has been 
collected frorn many localities along the African 
toast (CHENG, 1973 d) but has not hitherto been 
collected from the nearshore waters around Madagas- 
Cah. O.H.S.T.O.M., sér. Océanogr., vol. XII, no 2, 1974: 113-116. 
116 LANNA CHENG 
MALAGASY REPUBLIC 
(MADAGASCAR) 
Fig. 2. - Collecting stations in the Nosy Bc area. ( l = H. 
micans, 0 = H. germanus). 
car. Although extensive collections of planktonic. 
organisms have been made during the International 
Indian Ocean Expeditions, H. germanus has been 
found in only a limited number of samples, the 
majority of which came from nearshore waters 
(CHENG, in press B). 
CONCLUSION. 
Although only 27 samples were available for 
this study, they are of note since they came from 
an area around Nosy Be where the marine fauna is 
poorly known and from which Halobates has never 
been previously recorded. These collections thus 
add to our knowledge on the distribution and 
biology of these little-known oceanic insects. 
Acknowledgemenfs, 
1 am very gratcful to Dr. S. FRONTIER, Centre O.R.S.T.O.M. 
de Nosy Be, for sending me the samples used in this study, 
for criticizing the manuscript and for writing the French 
summary, and to the Foundation for Ocean Research, San 
Diego, for flnancial support. 
Manuscrit reçu au S.C.D. le 10 mai 1974. 
BIBLIOGRAPHY 
CHENG (L.), 1971. - Ocean-striders from Melanesia 
i (Hemiptera : Gerridae, Halobafes spp.) Cah. 
O.R.S.T.O.M., sér. Océanogr., 9 (4) : 513-518. 
CHENG (L.), 1973 a. - Soma Halobafes from the Pacifie 
Ocean. Jap. J. ZOO~., 17 (1) : 11-15. 
CHENG (L.), 1973 b. - Can Halobafes dodge nets 1 1 : by 
daylight 7 Limnol. Oceanogr., 18 (4) : 663-665. 
CHENG (L.), 1973 c. - The ocean strider Halobafes (Hete- 
roptera : Gerridae) in the Atlantic Ocean. Okeanologiya, 
13 (4) : 683-690 [in Russian]. 
CHEKG (L.), 1973 d. - Halobates. Oceanogr. Mar. Biol. 
Ann. Rev., 11 : 223-235. 
CHENG (L.) (in press, A). - Notes on the ecology of the 
oceanic insect Halobafes. Mar. Fish. Rev. 
CHENG (L.) (in press, B). - The ocean-strider Halobafes 
(Gerridae : Heteroptera). Proc. Symp. Indian Ocean 
and Adjacent Seas. J. Mar. Biol. Assn. India, 15. 
FRONTIER (S.), 1966. - Zooplancton de la région de Nosy-Bé. 
1. Programme des récoltes et techniques d’études. 
II. Plancton de surface aux stations 5 et 10. Cah. 
O.R.S.T.O.M. sér. Océanogr., 4 (3) : 3-37. 
HERRING (J. L.), 1961. - The genus Halobafes (Hemiptera : 
Gerridae). Pacifie Insecfs, 3 (2-3) : 223-305. 
PETIT (D.) and BOUR (W.), 1971. - Zooplancton d’une baie 
eutrophique tropicale ; II. Méthodologie des prélé- 
vements. Dot. Sci. Centre O.R.S.T.O.M. Nosy Bé 
No. 24, 8-24. 
Cah. O.R.S.T.O.M., sér. Océanogr., vol. XII, no 2, 1974: 113-116. 


Halobates (Heteroptera) : Gerridae) from the seas around Nosy Be, Magalasy

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