Sex ratio regulation in Brachymeria intermedia, a pupal gypsy moth parasitoid

1986 ◽  
Vol 64 (7) ◽  
pp. 1412-1415 ◽  
Author(s):  
M. A. Mohamed ◽  
H. C. Coppel
Keyword(s):  
Sex Ratio ◽  
Gypsy Moth ◽  
Intraspecific Competition ◽  
Host Density ◽  
Host Size ◽  
Male Density ◽  
Brachymeria Intermedia ◽  
Ratio Variables

The solitary pupal gypsy moth endoparasitoid, Brachymeria intermedia (Nees) (Hymenoptera: Chalcididae), regulates the sex ratio of its progeny such that the ratio is generally female skewed. Parents with a male-skewed sex ratio produce progeny that are female biased more than parents with a female-skewed sex ratio. Variables such as host size, host density, and intraspecific competition played no role in determining the sex ratio of the progeny. We conclude that sex ratio regulation of the progeny in this species is a function of male density.

scholarly journals SEX-RATIO MANIPULATION BY THE PARASITOID WASPMUSCIDIFURAX RAPTORIN RESPONSE TO HOST SIZE

Evolution ◽  
1993 ◽  
Vol 47 (6) ◽  
pp. 1876-1882 ◽  
Author(s):  
Sandra E. Seidl ◽  
Bethia King
Keyword(s):  
Sex Ratio ◽  
Host Size

Studies in Ovipositional Behaviour and Control of Sex in Aphytis Melinus Debach, a Parasite of California Red Scale, Aonidiella Aurantii (Mask.).

1974 ◽  
Vol 22 (2) ◽  
pp. 231 ◽  
Author(s):  
I Abdelrahman
Keyword(s):  
Sex Ratio ◽  
Host Density ◽  
Adult Emergence ◽  
The Body ◽  
Maturation Stage ◽  
Aphytis Melinus ◽  
Egg Maturation ◽  
Mean Size ◽  
Accepted Practice ◽  
And Control

The growing adult female red scale was the most preferred stage for A. melinus, followed by the second growing instar and lastly the male prepupa. The numbers of scale parasitized, the total of eggs laid, the number of eggs per scale, sex ratio and size of the parasites produced were all ranked in the same order. The mean size of parasites produced within the third instar decreased as the number of parasites per host increased. In the absence of the preferred host stages, female A. melinus laid readily in the unpreferred stages. In both A. melinus and A, chrysomphali it was noted that in multi- parasitism pupation, pupal development and adult emergence of all parasites in one host were synchronized. In A. melinus the sex and number of eggs laid per host are influenced by the host's size and quality. When A. melinus laid more than one egg in one host, it laid female eggs first and male eggs later; apparently the spermatheca goes through a period of fatigue, and is incapable of delivering sperm to the eggs descending the oviduct. Sex ratio decreases with increase in number of parasites per host and density of parasite population relative to hosts. The deposition of parasite eggs in a host by one female was observed during a short cycle of oviposition. A. melinus laid its eggs both 'above' and 'below' the body of the scale, whereas A. chrysomphali did so exclusively 'below'. In young mated A. melinus, eggs laid above the body of the scale were females and those below were males, but in old mated females all eggs, wherever laid, were male. Host development stops as soon as a parasite egg is laid. A. melinus avoids laying eggs in already parasitized hosts. The stages of red scale were ranked according to the percentage of mutilated individuals as: first moult (most mutilated), second instar, first instar, third instar, male prepupa and male pupa; second-moult females, egg-maturation stage and crawler-producing stage were unmutilated. A. melinus sometimes partitions her clutch of eggs into two hosts, particularly when host density is high. Partitioning in A. melinus may substitute for the generally accepted practice of super- parasitism, which would not be appropriate because the parasite is able to distinguish between parasitized and unparasitized hosts, is able to sense host density and to distribute her progeny on available hosts. Partitioning is advantageous for biological control. Behaviour of oviposition, mutilation and mutilation feeding in A. melinus are described in detail.

Superparasitism Occasionally Predisposes Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae) to Develop Gregariously in Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae)1

2002 ◽  
Vol 37 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Eric Wellington Riddick
Keyword(s):  
Sex Ratio ◽  
Spodoptera Exigua ◽  
Host Density ◽  
Adult Emergence ◽  
Cotesia Marginiventris ◽  
First Instar ◽  
Emergence Rate ◽  
Lepidoptera Noctuidae ◽  
Density Treatment

Experiments were designed to estimate the incidence of superparasitism of Spodoptera exigua (Hübner) and gregarious development of Cotesia marginiventris (Cresson). Dissections of host larvae revealed that superparasitism was common at all host densities (5, 10, or 20 larvae per 0.05 liter arena). At least two parasitoid eggs were present per host on day 1 after parasitoid oviposition; eggs were scarcely found on day 2 and never found on days 3, 4 or 5. More than one parasitoid first instar was present per host on day 2 at all densities, although more were found in hosts of the 5 density rather than the 20 density treatment. Second instars were present in hosts on days 3, 4 and 5, and at least one was present per host on day 5. Third instars (the final instar stage) were not present inside hosts by day 5. Rearing of host larvae demonstrated that gregarious development was rare, since less than 6% of parasitized hosts yielded two third instars that spun cocoons. Neither host density nor exposure time (24 h, 48 h) had an effect on the occurrence of gregarious development. The adult emergence rate was 64% and the sex ratio was male-biased for parasitoids that developed gregariously. The adult emergence rate was 73% and the sex ratio was unbiased for those that developed solitarily. This research suggests that superparasitism of hosts by C. marginiventris can occasionally predispose parasitoid larvae to develop gregariously. Frequent superparasitism of hosts may be detrimental to the long-term propagation of C. marginiventris.

Sign in / Sign up

Export Citation Format

Share Document