Allee effects: population growth, critical density, and the chance of extinction

It is postulated that the sperm precedence characteristics of most insect populations have resulted primarily from selection on females (1) to optimize the genetic composition of their progeny; (2) to discourage or encourage multiple matings for reasons other than genetic considerations; (3) to optimize their sperm storage capacity and utilization. In addition, selection on males to maximize egg fertilization by reduced displacement of their sperm and increased displacement of other sperm to the extent that these can be achieved without sacrificing the optimal mating strategy (Parker 1970a) probably has been important in some species. Parker's (1970a) hypothesis that the amount of sperm displacement in a population should stabilize at the value which yields the optimal overall male fertilization rate is accepted as the optimal male strategy; however, it is suggested that females often largely determine, by their behavior and by the structure and functioning of their reproductive tract, the optimal male st...

https://www.jstor.org/stable/info/2460800

Sperm Utilization Strategies in Nonsocial Insects

Summary
1. The paper summarizes the published evidence on the relation between mating frequency and fecundity in insects. There is experimental evidence of varying quality for 63 species and non-experimental evidence for about 60.

2. Repeated mating may be universally necessary for full fecundity and fertility in female insects (in species in which the females normally mate more than once).

3. The evidence is remarkably poor. We need more properly designed experiments (and not just observations of natural variation), with sufficient sample sizes and statistics, and measurements of the fecundities and fertilities of singly and multiply mated females, when the multiple matings are separated by many days or weeks. Most of the existing experiments of this sort are defective in some way.

4. In species with greater total fecundity and longevity, multiple mating may be more likely to enhance fertility than in species with small fecundity and short life span.

5. Females in naturally monandrous species do not show increased fecundity or fertility with repeated mating, whereas females of polyandrous species do.

6. There is no obvious connexion between paternal investment, in so far as we know about it, and the increase of fecundity by repeated mating.

7. There is a small tendency for females to breed more quickly and be shorter lived if they mate repeatedly.

Mating frequency and fecundity in insects.

The chapter focuses on the understanding of the mechanisms of sperm competition, which are essential for interpreting nonrandom patterns of paternity and for predicting the types of adaptations that sperm competition can generate. P2 values are often used to infer the mechanism of underlying patterns of sperm utilization: intermediate values are taken as indicative of sperm mixing while higher values of P2 are taken as evidence for sperm precedence or sperm displacement. The bimodal distribution of P2 values seen in Lepidoptera is an excellent example of how little the mean value of P2 can tell us about the patterns of sperm competition. Patterns of sperm competition can change markedly with changes in the intervals between copulations. It is clear that males can adjust the numbers of sperm ejaculated into females, depending on female quality and/or the risks of sperm competition. Thus, patterns of sperm utilization depend on the behavior of males. Alternatively, they also depend on the responses of females to males that vary in their quality as mates. Variation in the numbers of sperm inseminated into the female prior to the final mating can have marked effects on the patterns of sperm utilization.

10 – Sperm Competition in Insects: Mechanisms and the Potential for Selection

Publisher Summary This chapter describes sterile insect techniques (SIT). It is a biologically based method for the control of key insect pests. Wild female insects inseminated by released, radiation-sterilized males do not reproduce, and repeated releases of the sterilized insects lead to a reduction in pest population numbers. Effective control using sterile insects is achieved when they are used systematically as part of area-wide integrated pest management (AW-IPM) programs. SIT is species-specific, nonpolluting, and resistance-free. Since the original concept was developed in the United States in the 1940s, SIT has been used successfully for screwworm flies, tsetse flies, fruit flies, and moths. Technical progress in behavioral ecology, mass rearing, strain improvement, global information, positioning and monitoring systems, and aerial release, combined with economies of scale and a growing demand for pest-free and low-pesticide agricultural products in local and international trade, have increased the use of SIT in AW-IPM programs. These programs, by decreasing insecticide use, have also facilitated the use of biological control agents against secondary insect pests.

/pdf/sterile-insect-technique-xi6er5rwhs.pdf

Sterile Insect Technique

Sterile oriental fruit flies, Dacus dorsalis Hendel, emerging on Guam from 36 million irradiated pupae placed at the loci of infestations established with traps baited with methyl eugenol eradicated the abnonnally small population present after host crops were destroyed by typhoons Karen in 1962 and Olive in 1963. The several reintroductions that occurred in 1964 and 1965 before effective quarantines were established were eradicated by the same method before September 1965. Similar releases on Saipan and Tinian were not successful; too many flies died before reaching sexual maturity, perhaps because sufficient natural food was lacking near the emergence sites (honeydew-producing insects were suppressed by the typhoons) and because of damage by overheating during movement from Guam to field cages on Saipan. Eradication was finally achieved on these islands in 1965 by distributing fiberboard squares impregnated with methyl eugenol and naled every 2-week period for 41/2 months (method of male annihilation). The Mariana Islands, which have been infested with the oriental fruit fly for at least 35 years, have now been free of the species for more than 4 years.

Eradication of the oriental fruit fly from the mariana islands by the methods of male annihilation and sterile insect release.

Tests of mating behavior in the laboratory showed that Ceratitis capitata (Wiedemann) males are polygamous; however, 40% of the females did not remate. Among remating females (96 of 173), 75% remated 1–2 times in 49 days. Female receptivity to remating apparently correlated with the volume of stored sperm in the spermathecae.

Reproduction of the Mediterranean Fruit Fly:Frequency of Mating in the Laboratory

Proteinaceous food baits in water traps were 20X more efficient in trapping oriental fruit flies, Dacus dorsalis Hendel, in a dry climate (less than 25 cm avg annual rainfall) than in a wet climate (400 cm). Greater efficiency also was observed in a dry climate with the melon fly, D. cucurbitae Coquillett, and the Mediterranean fruit fly, Ceratitis capitata (Wiedemann).

Tephritid Fruit Fly Trapping: Liquid Food Baits in High and Low Rainfall Climates

A solution of 5% naled (wt/wt) in cue-lure, soaked on 2×2×½-inch fiberboard blocks at a rate of about 1 ounce per block reduced populations of male Dacus cucurbitae Coquillett more than 99%, based on trap catches in a 2-square-mile plot in Hawaii when the blocks were suspended 2 to 5 feet above ground in a grid pattern with 0.9 blocks per acre. In a small 5-acre area of the plot with a more favorable habitat, supplementary distribution of blocks at the rate of 5.4 per acre was necessary. The blocks maintained their effectiveness undiminished for over 7 months in the field despite heavy rainfall.

Field Trial of Cue-Lure + Naled on Saturated Fiberboard Blocks for Control of the Melon Fly by the Male-Annihilation Technique

Mass-trapping of male oriental fruit flies, Dacus dorsalis Hendel, with methyleugenol plus malathion at the rate of nine saturated fiberboard blocks per ha produced male population reductions >99% in a papaya orchard (63 ha). However, because the surrounding jungle was not trapped, fruit infestation rate was reduced only 48%.

Male annihilation through mass-trapping of male flies with methyleugenol to reduce infestation of oriental fruit fly (Diptera: Tephritidae) larvae in Papaya

R. T. Cunningham

Papers

Eradication of the oriental fruit fly from the mariana islands by the methods of male annihilation and sterile insect release.

Reproduction of the Mediterranean Fruit Fly:Frequency of Mating in the Laboratory

Tephritid Fruit Fly Trapping: Liquid Food Baits in High and Low Rainfall Climates

Field Trial of Cue-Lure + Naled on Saturated Fiberboard Blocks for Control of the Melon Fly by the Male-Annihilation Technique

Male annihilation through mass-trapping of male flies with methyleugenol to reduce infestation of oriental fruit fly (Diptera: Tephritidae) larvae in Papaya