Anastrepha suspensa

Anastrepha suspensa females lay about 200 eggs on the exterior of mature and rotting fruit.[9][10] The eggs are laid and will hatch in flavedo part of the fruit.[15] A. suspensa eggs are elliptical in shape.[1][3][16] The color of these eggs ranges from pale to gleaming white. The anterior end of the egg contains a micropyle, which is an opening for the sperm to enter. On the same end of the egg there is a characteristic polygonal pattern in the surface architecture of the chorion.

The larvae which hatch from the eggs are vermiform maggots, similar to other fruit flies. They possess an elongated and cylindrical shape. These larvae progress through 3 instars, or stages between molting. First instar larvae appear clear to pale white. During this period, the mouth hooks are formed and become the main feature.[9] These two sets of thin brown hooks are located on the ventral surface of the larvae. The color of second instar larvae begins to change towards a pale cream color.[9] In this stage, the larvae will begin to develop features like the anterior spiracles to allow oxygen to enter the respiratory system.[9] They will also start to develop small oral ridges and black mouth hooks. Third instar larvae transition from a cream to a light yellow color and are about 8 to 10 mm in length. During this the time, the overall body surface becomes rough and the morphology of the larvae solidifies. The mouth hooks have now transformed into a single pair of sharp, black teeth that are strongly sclerotized.[9] The oral ridges become more distinct, and there are creeping welts that begin to form.[9] Due to the close resemblance of A. suspensa and other species in Anastrepha, it can be difficult the accurately identify A. suspensa larvae.

Larvae and pupae advance from the flavedo towards the center and pulp sections of the fruit as it matures because of the increased sweetness.[17] This then leads to more rapid development.[17] Larvae may feed on the fruit constantly over a 24 hour period. No group sociality has been observed apart from feeding on the same areas.[15]

After completing growth as a larva, the immature A. suspensa transition into a pupa. The pupae are fully encompassed by the hardened skin of the 3rd larval instar which forms a covering called a puparium.[9] The pupae possess an ellipsoid shape and appear golden to reddish-brown. During this phase, there are visible spiracles on the anterior surface that allow for respiration. After completing pupation, the adult fly breaks out of the puparium.

While mating studies were conducted during spring and summer, this species does not undergo winter diapause, so mating behavior may occur throughout the year.[18] During the early morning, males and females often interact on host fruit like guava and Cayenne cherries. The males will be feeding and courting, and the females will be feeding and ovipositing.[18] As temperature and light increase as the morning progresses, males and females will both move to areas under shaded leaves.[18] In afternoon and late afternoon, males compete for single-leaf territories. Since territorial fights are a crucial component to mating; flies that were larger could claim larger territories, demonstrated higher levels of fitness, and had better matting success.[18][10][19] In these claimed areas, the males puff to release sex pheromones from glands near their anal canal as scent markings[20][21] and sing songs to attract females.[22] These pheremones are used as scent markings.

Male A. suspensa make two distinct sounds towards females: the calling song and the precopulatory song.[22][23] Both of these sounds are created through rapid wing vibrations by the male fly.[22][23] Male fitness can be communicated through the songs as larger males produce more intense songs.[22][23] Male size seems to be negatively correlated with frequency of calling songs, but there is no correlation between male size and frequency of precopulatory songs.[22][23] Females are attracted to areas where the calling song is broadcast, but more research is needed to determine if calling males have higher mating success than males that do not call.[22][23]

Since unsuccessful precopulatory songs were not as loud and had a broader bandwidth than that of successful songs, it is believed that the precopulatory song may be the last acoustic opportunity for males to display their fitness to the female.[22][23] This could explain greater mating success for better males giving precopulatory songs due to increased female compliance once a male has mounted. However, longer precopulatory songs correlate with shorter matings. This is thought to occur because longer precopulatory songs are employed by males with mates that are less sexually responsive; therefore, the longer song may be just enough to lead to mating.[22][23] Since larger males coupled longer, it is believed that the increased strength that comes with size helps in a conflict of interest when it comes to mating between males and females.[22][23]

The eggs may be deposited in groups or as individuals based on the size of the fruit.[15] As a form of egg guarding and to prevent overpopulation in a fruit, A. suspensa females have deposit pheromones from anal membranes that deter repeated attempts of oviposition in a fruit.[21] This water-soluble pheromone may deter additional oviposition attempts by A. suspensa for at least 6 days.[21] The plant compounds naringin and quinine inhibit oviposition, reducing the areas in which A. suspensa may inhabit and reproduce.[24]

A. suspensa on a leaf

It has been shown that flight in A. suspensa may be influenced by age, size, sex, and weight. On average, adult A. suspensa can fly 120 kilometers, which allows for the spreading of the species.[1] Studies have examined the effect of gamma irradiation on flies at different stages of their life to make them sterile. It was observed that females that were treated with gamma irradiation fly farther and faster early in their life than untreated females but slower later in their lives.[29] This difference may be due to affecting the female's role in reproduction. For males, being sterilized by gamma irradiation did not produce significant differences.[29] Gamma radiation also changed the waveform of the sound created by the wings of the flies. By sterilizing the pupae, it was observed that wing beat frequency decreased.[29]

While most studies on A. suspensa have been in a laboratory setting, the results have been telling for the set-up of vision in A. suspensa. Research has shown clear inclinations for A. suspensa towards objects that are colored orange.[30] This preference is then followed by yellow and yellow-green. Colors that did not greatly attract A. suspensa were dark green, red, blue, white, and black.[30] Based on these preferences, it was hypothesized that the photoreceptors in A. suspensa respond specifically to 580-590 nm visible light range. Responses to this light range seems to correspond with fruit seeking. Other studies have discussed the strong sense of vision for A. suspensa and how this has allowed for conducting experiments with clear cages to further test the behavior of the flies.[30]

In the process of creating a better way to search fruits for the presence of A. suspensa larva than cutting the fruit, scientists discovered that A. suspensa larvae and pupae create sounds while chewing.[17] While the interactions based on sound between organisms at this age have not been studies, the sounds are important for scientists in understanding the life cycle in terms of feeding with A. suspensa[17].

Since larvae burrow beneath the surface of fruits that they occupy, it is difficult to observe feeding behavior of these early stages of the flies. In adult A. suspensa, it has been noted that food coloring does not affect the fitness parameters of the flies. Additionally, it was learned that A. suspensa ingested both liquids and solid particles. This information elucidated a feeding mechanism similar to that of the Mediterranean fly.