Relationship of age, ovarian development, and the corpus allatum to mating in the house-fly, Musca domestica

Rearing methods of four insect species intended as feed, food, and food ingredients: a review

Over the past 2 decades, the potential of insects as food and feed has been recognized globally. Insects as feed ingredients can improve sustainability because of their lower greenhouse gas emissions and their potential to transform organic wastes into high-quality feed rich in nutrients. However, currently, the practical use of insects as food or feed is limited by the high costs of insect production. A great deal of effort is required to improve the rearing technology necessary to establish the principles of insect farming. Several insect species have become industrialized using existing methods of production. The most common industrialized insect species intended as feed and food include the yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae); the house cricket, Acheta domesticus L. (Orthoptera: Gryllidae); the black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae); and the house fly, Musca domestica L. (Diptera: Muscidae). This review focuses on describing the existing rearing methods for these 4 insect species, which may provide a basis for future research to enhance insect production capabilities.

Rescuing the Inhibitory Effect of the Salivary Gland Hypertrophy Virus of Musca domestica on Mating Behavior

Infection with salivary gland hypertrophy virus (MdSGHV) of Musca domestica prevents female flies from accepting copulation attempts by healthy or virus-infected males. This study focused on supplemental hormonal rescue therapy for mating behavior in virus-infected female house flies. The inhibitory effect of the virus on mating behavior in females injected with MdSGHV was reversed by hormonal therapy in the form of octopamine injections, topical application of methoprene, or both therapies combined along with 20-hydroxyecdysone. Infected females whose mating responsiveness had been restored continued to have other viral pathologies associated with infection such as hypertrophy of the salivary glands and a lack of ovarian development.

Time Flies-Age Grading of Adult Flies for the Estimation of the Post-Mortem Interval

The estimation of the minimum time since death is one of the main applications of forensic entomology. This can be done by calculating the age of the immature stage of necrophagous flies developing on the corpse, which is confined to approximately 2–4 weeks, depending on temperature and species of the first colonizing wave of flies. Adding the age of the adult flies developed on the dead body could extend this time frame up to several weeks when the body is in a building or closed premise. However, the techniques for accurately estimating the age of adult flies are still in their beginning stages or not sufficiently validated. Here we review the current state of the art of analysing the aging of flies by evaluating the ovarian development, the amount of pteridine in the eyes, the degree of wing damage, the modification of their cuticular hydrocarbon patterns, and the increasing number of growth layers in the cuticula. New approaches, including the use of age specific molecular profiles based on the levels of gene and protein expression and the application of near infrared spectroscopy, are introduced, and the forensic relevance of these methods is discussed.

Effect of Diet on Adult House Fly (Diptera: Muscidae) Injected With the Salivary Gland Hypertrophy Virus (MdSGHV)

Research to date on the salivary gland hypertrophy virus (SGHV) in three species of flies has focused on adult flies having access to and taking a proteinaceous diet. Since many studies have shown that diet affects viral infection in numerous organisms, this study examined the effect of a protein-free diet on the effect of the SGHV virus in adult house flies, Musca domestica. L. Adults infected with the virus, and maintained on a sugar diet only, showed salivary glands with a blue rather than a grayish color and mild hypertrophy compared with protein-fed flies. It was possible to retrieve the virus from these glands and successfully infect noninfected flies. When injected at various ages, female flies fed only sugar showed that regardless of age, sugar-fed flies still became infected and showed the pathology of the glands. In addition, electron microscope studies revealed at the ultrastructural level that there was no difference between viral replication in cells from salivary glands of adults fed a proteinaceous-free diet and those feeding on protein.

Interactions among mechanisms of sexual selection on male body size and head shape in a sexually dimorphic fly

Darwin envisaged male-male and male-female interactions as mutually supporting mechanisms of sexual selection, in which the best armed males were also the most attractive to females. Although this belief continues to predominate today, it has been challenged by sexual conflict theory, which suggests that divergence in the interests of males and females may result in conflicting sexual selection. This raises the empirical question of how multiple mechanisms of sexual selection interact to shape targeted traits. We investigated sexual selection on male morphology in the sexually dimorphic fly Prochyliza xanthostoma, using indices of male performance in male-male and male-female interactions in laboratory arenas to calculate gradients of direct, linear selection on male body size and an index of head elongation. In male-male combat, the first interaction with a new opponent selected for large body size but reduced head elongation, whereas multiple interactions with the same opponent favored large body size only. In male-female interactions, females preferred males with relatively elongated heads, but male performance of the precopulatory leap favored large body size and, possibly, reduced head elongation. In addition, the amount of sperm transferred (much of which is ingested by females) was an increasing function of both body size and head elongation. Thus, whereas both male-male and male-female interactions favored large male body size, male head shape appeared to be subject to conflicting sexual selection. We argue that conflicting sexual selection may be a common result of divergence in the interests of the sexes.

Lifetime ovipositional patterns of mated and virgin onion flies, Delia antiqua (Diptera: Anthomyiidae)

Over their 47.2+/-1.9 (mean+/-SEM) day lifespan, mated onion flies, Delia antiqua, oviposited more uniformly than did virgins. Mated females began ovipositing at 6.4+/-0.2 days old and regularly deposited 14.2+/-0.6 eggs/day for 3-4 weeks. Thereafter, oviposition slowed and stopped at about 1 week before death. Virgin flies began ovipositing 24.7+/-1.5 days into their 59.0+/-3.8 day lifespan, and deposited eggs at an increasing rate for 3-4 weeks, generating a mean overall ovipositional rate of 5.8+/-0.5 eggs/day. The later onset of virgin oviposition (ovipositional activation) and not a shorter ovipositional period largely accounted for the disparity between virgin and mated female lifespans. Mean lifetime egg production of mated females was 475+/-27 eggs versus 179+/-30 eggs for virgins. Ovipositional and post-ovipositional periods (34.4+/-1.8 and 7.2+/-1.0 days) for mated females were not significantly different from those of virgin females (30.9+/-3.6 and 6.7+/-1.2 days). Over 90% of virgin females laid eggs. The distinction between mated and virgin ovipositional patterns may be specifically attributed to differences in: (1) egg maturation, (2) age at ovipositional activation, and (3) egg-laying rate.

Regulation of mating behavior by nutrition and the corpus allatum in both male and female Phormia regina (Meigen)

Both dietary protein and the corpus allatum (CA) were required for normal mating behavior in both male and female black blow fly, Phormia regina (Meigen). Nutrition (protein diet) activated the CA in both sexes. More than 10 mg of dietary liver was required for each male to result in 80% insemination of females, while 20 mg of liver was required for each female to allow 78% of females to become inseminated. Between 10 to 15 mg of protein meal (i.e., liver) was required to activate sexual receptivity in 71% of the females, while between 15 to 20 mg of liver was needed to support full oöcyte development in 70% of the females (Yin, C.-M., Zou, B.-X., Li, M.-F., Stoffolano, J.G., Jr. 1994. Discovery of a midgut peptide hormone which activates the endocrine cascade leading to oogenesis in Phormia regina Meigen. Journal of Insect Physiology, 40, 283-292). Allatectomy suppressed mating behavior more than 2-fold in both sexes. Topical application of 10 &mgr;g of S-methoprene (a juvenile hormone analogue) at 12 h after the onset of liver feeding restored sexual activity of both allatectomized males and females. Incidence of successful insemination increased as the oöcyte development progressed. Ovariectomy suppressed sexual receptivity more than 3-fold in liver-fed females. Thus, in addition to nutrition and the CA, ovaries and their developmentaal status can also affect the sexual receptivity in female P. regina.

Parallel control mechanisms underlying locomotor activity and sexual receptivity of the female German cockroach, Blattella germanica (L.)

We have studied the effects of ovaries, juvenile hormone (JH) and mating on locomotor activity and sexual receptivity of female German cockroaches. Our results indicate that locomotor activity and sexual receptivity are under the same control mechanisms. The ovary served as a negative masking factor for the locomotor circadian rhythm, but did not affect the frequency of locomotor activity. We conclude that JH controls the locomotor activity of females from the following evidence: (1) increasing locomotion of virgin females coincided with an increasing volume of the corpora allata; (2) allatectomy reduced female locomotion significantly; (3) after absorbing the JH analogue (fenoxycarb) through their tarsi, allatectomized females regained their high level of locomotor activity. Since the daily locomotor activity of allatectomized and ovari-allatectomized females changed cyclically with continuous (non-cyclic) contact of fenoxycarb, an unidentified factor which was independent of ovarian development is proposed to regulate cyclic locomotor activity. In addition to controlling the frequency of locomotor activity, JH was essential for the expression of the locomotor circadian rhythm because allatectomy abolished the circadian rhythm expressed in ovariectomized females. Mating significantly decreased the frequency of locomotor activity and the degree of sexual receptivity. The inhibitory effect of mating resulted from the transmission of a mating signal through the ventral nerve cord when sperm was transferred successfully. The mating experiments with allatectomized and ovariectomized females showed that JH was the major factor in regulating the expression of sexual receptivity.

Relationships among hormonal changes, cuticular hydrocarbons, and attractiveness during the first gonadotropic cycle of the female Calliphora vomitoria (Diptera)

Attractiveness in adult females of Calliphora vomitoria is correlated with ovarian development and there is a marked increase during the previtellogenic and vitellogenic periods. The development of attractiveness may result from the combined actions of ecdysteroids and juvenile hormone. A rise in total hydrocarbons parallels the first increase in levels of these hormones during the previtellogenic stage. Cuticular hydrocarbons subsequently fall, along with the disappearance of hemolymphatic ecdysteroids, and then rise again during the vitellogenic phase of JH production. Increasing and decreasing of some cuticular hydrocarbons, some hydrocarbons implicated in the attractiveness, are correlated with variation of the titer of these hormones, especially JH III.

Differences in mating propensities: some models for examining the genetic consequences

Several models of mating behavior are described. The rates at which matings occur are described by differential equations. When several types of males are present with several types of females, the rates are described by a system of such equations. Different modes of pair formation result in different equations, and differences in mating propensities result in different constants in the equations. Two types of pair formation are examined: promiscuous pair formation and permanent pair formation. these models are found satisfactory when tested against observations of mating in flour beetles and houseflies. Some ways in which different mating propensities may affect the genetic structure of populations are examined in the light of these models.