Oviposition behaviour of Gryon gallardoi (Hym.; Scelionidae) on eggs of Spartocera dentiventris (Hem.; Coreidae)

Abstract

The oviposition behaviour of Gryon gallardoi (Hymenoptera; Scelionidae) on Spartocera dentiventris (Hemiptera; Coreidae) host eggs was investigated in the laboratory. Masses of 12 non-parasitized freshly laid (less than 24 h old) eggs were exposed to 2-5 days old mated females with previous oviposition experience (n = 10). Behaviour was observed for 2 h under the stereomicroscope. The eggs were Then kept individually at 25 degrees +/- 1 degree C/12 h photophase till hatching. The mean number of parasitized eggs was 7.8 +/- 0.81 (mean +/- SE). Five distinct kinds of behaviour were observed: drumming with antennae on the eggs, ovipositor insertion, egg marking, walking and resting. On average, ovipositor insertion was not followed by marking 4.3 +/- 0.76 times per female. In nearly all of these events, parasitism was unsuccessful. Walking and resting were observed less frequently than the other behaviours (1.6 +/- 0.56 and 2.1 +/- 0.48 times/female, respectively). Superparasitism occurred on average 3.6 +/- 0.88 times per egg mass, with 2.7 +/- 0.57 eggs being superparasitized. Among these, on average 87.4 +/- 5.37% led to successful development of an adult parasitoid. The average time spent on the each kind of oviposition behaviour was 1.5 +/- 0.57 min for drumming, 3.9 +/- 0.56 min for ovipositor insertion and 0.4 +/- 0.06 min for marking. There was no significant variation on the duration of each behaviour as the parasitoid progressed in parasitizing an egg mass. Ovipositor insertion almost always (87.58%) occurred in the longitudinal extremities of the egg. In average 31.1 +/- 7.21% of the individual emerging per egg mass were males, the larger proportion of males originating from the 2nd oviposition. The results show a range of oviposition behaviours common to the Scelionidae family. Egg marking behaviour was a good indicator of the effective oviposition by females. Superparasitism is only partially avoided, but its occurrence does not imply a failure of parasitoid emergence. The sex ratio is skewed towards females, and most males come from the first ovipositions.

Oviposition behaviour of Gryon gallardoi (Hymenoptera, Scelionidae) on eggs of different ages of Spartocera dentiventris (Hemiptera, Coreidae)

“…Parasitoids were kept in transparent plastic cages under controlled conditions (25 ± 1ºC and 12 h photoperiod) until adult emergence. Adult parasitoids used in the experiments were kept under these same conditions and fed on a 10% honey solution (WIEDEMANN et al, 2003) We used mated parasitoid females between two and five days of age, kept confined with egg groups of S. dentiventris for 24 hours to acquire oviposition experience. Afterwards, each female was exposed individually and without choice to a non-parasitized egg group of each of the following ages: 2, 3, 4, 5, 6, 7, 8 and 12 days, in a test tube (1 x 6 cm) closed with a cotton stopper.…”

“…Observations were done with the aid of a stereomicroscope with cold light, during two hours, from the moment the female first manifested interest in the egg group. For each egg group of a given age, the behavioural processes of the G. gallardoi female were recorded according to the classes proposed by WIEDEMANN et al (2003), with the description and duration of each process obtained vocally with the help of a tape recorder and chronometer. Self-parasitism was recorded as so when a female of G. gallardoi inserted the ovipositor and marked an egg more than once (WIEDEMANN et al, 2003), with behaviours toward these eggs also recorded.…”

“…In this context, a series of researches have been developed worldwide, both with egg parasitoids of solitary or semi-gregarious habits (STRAND & VINSON, 1983;NAVASERO & OATMAN, 1989;COLAZZA et al, 1996;CONTI et al, 1997;ROSI et al, 2001;SOLIS et al, 2001;HIROSE et al, 2003;WIEDEMANN et al, 2003;DASILAO & ARAKAWA, 2004) and with those of gregarious habits SCHIMIDT & SMITH, 1987;HINTZ & ANDOW, 1990;RUBERSON & KRING, 1993).…”

“…The authors recorded six behavioural processes: host selection, choice of ovipositor insertion point, oviposition, marking, cleaning and resting. WIEDEMANN et al (2003) described, in the laboratory, the oviposition behaviour of G. gallardoi on one day-old S. dentiventris eggs. Five distinct behaviours were recorded: drumming, ovipositor insertion, egg marking, walking and resting.…”

Dispersal of the egg parasitoid Gryon gallardoi (Brethes) (Hymenoptera: Scelionidae) in tobacco crops

“…; scelionidae) in the control of S. dentiventris have demonstrated that this species is responsible for about 50% of the egg mortality observed for the bug (santos et al, 2001). several laboratory and field studies have involved investigations into the G. gallardoi -S. dentiventris interaction (Wiedemann et al, 2003;canto-silva, 2003). Jesus et al (2002a,b) studied the spatial dispersion and movement pattern of the coreid on tobacco plants.…”