Proc. Int. Soco Citriculture,
1227-1228. 1992.
Courtship and Mating Behaviour in Aphelinus chaonia Walker
(Hym.: Aphelinidae), an Important Parasitoid of Toxoptera aurantii
(B.D.F.) (Hom.: Aphididae). Preliminary Note
G. Líotta
Institute of Agricultural Entomology, University of Palermo, Italy
S.Manzella
Osservatorio per le Malattie delle Piante Palermo, Assessorato Agricoltura e Foreste Regione Siciliana, Italy
Additional index words. mount, dismount, antennation, copulation
Abstract.
Courtship and matlng behaviour was studied in 113 pairs of Aphelinus chaonia Walker (Hymeooptera:
Aphelinidae), introduced ioto gelatioe capsules at the experimental conditioos of25-27 "C, R.H. 70-80% aod oatural
IIght. 85.84% of pairs showed the followlng sequeoce: antennal contact, mount, post mount antennation, copulatioo,
post copulatory antennatioo, dismount. The entire sequence ofevents lasted on average x= 63.20 ;1;.21.08(0= 97).9.73 %
of pairs showed some difTerences in the intermediate phases of the sequences, while 4.43 % did oot mate.
It is well known that knowledge of bio-ethological behaviour
can be very helpful in evaluating the capacity of parasitoids to
control biologically their host phytophages.
In recent times, various studies have been carried out on the
courtship and mating of hymenoptera aphelinids (Khassimuddin
and DeBach, 1975; Gordh and DeBach, 1978; Mazzone, 1983;
Viggiani and Battaglia, 1983, 1984; Viggiani et al., 1986;
Battaglia et al., 1988; Lo Pinto, 1989) and inter-specific differences have been shown up that can be used for systematic aims.
The aim of the present research is to investigate the courtship
and mating of A. chaonia (Hymenoptera: Aphelinidae), which in
Sicily plays an important role in controlling some aphids, includingAphisfabae Scopoli and Toxoptera aurantii (B.D.F.) (Liotta,
1983, 1988).
Materials and Methods
The observations were carried out in a laboratory and the
experimental conditions were temperature 25-27 °C, relative
humidity 70-80% and naturallight.
From colonies of A.fabae, bred on Galium aparinae L. and
parasitised by A. chaonia, aphid mummies were isolated in
gelatine capsules (length 2 cm, diameter 0.7 cm)
Within 24h after post-emergence, adults were placed in pairs
in the capsules and observed under stereo-microscope for 15
minutes. Sexual interactions, pre-courtship times and timing of
the courtship and mating sequence were noted down.
Sexual behaviour was observed in 113 pairs.
Moreover, females which had mated were put back into
capsules together with the males from the first copulation or
different males that had mated, for a repetition of mating after 3,
6, 12 and 24 hours, 10 pairs being used for each trial with a total
of 80 pairs.
To check the capacity of males that had mated to repeat
copulation, they were put into capsules with virgin females 3, 15,
30 and 60 minutes after the first copulation, 4 pairs being used for
each trial with a total of 16 pairs.
Results and Discussion
In 95.57% of the pairs observed (108/113) copulation ocThis work was supported by M.U.R.S.T. (60%).
Proc. Int. SocoCitriculture, 1992, Vol. 3.
curred, and in 85.84% of cases (97/113) there was a typical
sequence of courtship and mating, while in 9.73% of cases (11/
113) there were differences in the intermediate phases of the
sequence. In the remaining 4.43 % of pairs (5/113) copulation did
notoccur.
In this preliminary note, we discuss only the most frequent
sequence, involving the following phases: antennal contact,
mount, post-mount antennation, copulation, post-copulatory
antennation, dismount.
The whole sequence appears to be less composite than in other
aphelinids like Encarsia asterobemisiae Vigg. and Mazz.
(Viggiani and Battaglia, 1983) and Cales noacki How. (Lo Pinto,
1989), - which exhibit articulated post-copulatory courtship but
more complicated than in Encarsia pergandiella Howard
(Viggiani and Battaglia, 1983) and Coccophagus obscurus
Westw. (Battaglia et al., 1988), in which both post-mount and
post-copulatory antennation are absent.
After being placed in the capsules, the individuals move at
random or remain motionless and distant Interception is always
on the part of the male, which for brief instants follows the female
in 75.26% of cases (73/97), while if the female is stationary it
approaches with caution. The precourtship period has a duration
of x= 57.42 ± 46.91 sec (n= 97), as in C. noacki, in which this
period takes on mean values around one minute (Lo Pinto, 1989).
Inception of the courtship sequence starts with brief antennation
by the male, performed generally near the female' s gaster. Mount
is posterior, as in Eretmocerus longicomis Vigg. and Batt.
(Battaglia et al., 1988) but differs from that of Encarsia
aspidioticola (Mercet) (Viggiani and Battaglia, 1984), in which
it is lateral.
The male heads rapidly for the female's head, walking on its
back in order to perform post-mount antennation. It places itself
with its front legs on the female' s head, its back legs on her wings,
and its middle legs raised without touching the female' sbody, like
Aphytis lingnanensis Compere (Gordh and DeBach, 1978) and
Physcus testaceus Masi (Viggiani et al., 1986).
Male antennation in A. chaonia comes about through alternating vibration of both appendices, which stick out below in front
of the female's, usually in a reclining position, unlike C. noacki
in which the female's antennae are stretched out at the front (Lo
Pinto, 1989). The duration of post-mount courtship is x= 19.35 ±
6.27 sec (n= 97).
Subsequently,themalemovesbackquickly,bendsitsbodyand
1227
brings its genital aperture against the fernale's for a brief period
(x= 2.19 ± 1.30 sec; n= 97), while the fernale rernains rnotionless
throughout the copulation, as in Aphytis lingnanensis Cornpere
(Gordh and DeBach, 1978) and C. noacki (Lo Pinto, 1989).
Unlike Archenomus
longiclava (Girault), Encarsia
asterobemisiae (Viggiani and Battaglia, 1983)and C. noacki (Lo
Pinto, 1989), aftercopulation theA. chaonia male rnoves forward
rapidly without disrnounting. It perforrns post-copulatory
antennation, to which the fernale responds by raising both antennae towards the rnale' s, for a duration of x= 37.49 ± 18.52 sec (n=
97).
At the end of courtship, the fernale begins running on the
substraturn and the rnale disrnounts brusquely. As in the case of
C. noacki (Lo Pinto, 1989), it is the fernale that interrupts the
sexual interaction, while in Aphytis lingnanensis Cornpere either
sex can do it independently (Gordh and Debach, 1978).
The overall duration of the courtship and mating sequence in
A. chaonia is x= 63.20 ±21.08 sec (n= 97), less than thatreported
for Archenomus longiclava (Viggiani and Battaglia, 1983) and C.
noacki (Lo Pinto, 1989).
In the trials carried out, inserninated A. chaonia fernales never
consented to a second courtship. As in the case of Aphytis spp.
(Khasirnuddirn and DeBach, 1975), it is to be supposed that the
A. chaonia fernale mates only once in her lifetirne, at least frorn
trials carried out within 24 hours of the first copulation.
On the other hand, males that had rnated and were then placed
in contact with virgin fernales always copulated, even 3 rninutes
after the previous copulation, like Encarsia partenopea Masi
males, which can mate again within a few minutes (Mazzone,
1983), as can Encarsia aspidioticola (Mercet) males (Viggiani
and Battaglia, 1984).
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PrOC.Int. SocoCitriculture, 1992, Vol. 3.