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= Liriomyza Trifolii =

Liriomyza trifolii, known generally as the American serpentine leafminer or celery leafminer, is a species of leaf miner fly in the family Agromyzidae. L. Trifolii is a damaging pest, as it consumes and destroys produce and other plant products. It commonly infests greenhouses. It is found in several countries around the globe, but primarily in the Caribbean and southeastern United States.

Description
Adult L. trifolii typically measure less than 2 millimeters in length. They are mostly yellow in color, although parts of the abdomen and thorax are dark brown or grey in color. A key distinguishment between the L. trifolii and L. Sativae are the dark, matte mesonotum.

L. trifolii typically have a wingspan of 1.25 to 1.9 milimeters. Their wings are transparent and have veins in the same pattern as the rest of the Phytomyzinae family, as shown in the image.

Distribution
L. trifolii used to be found solely in Caribbean countries, southeastern United States (specifically concentrated in southern Florida), and certain parts of Canada. However, export of produce and other vegetative goods from these areas has led to the dispersion of L. trifolii to several countries in Asia along the Pacific Ocean, as well as Europe and California. This human-facilitated dispersion occurred mostly after L.trifolii became resistant to insecticides, and therefore were not killed off by the exports' treatment with before and after transport.

Habitat
L. trifolii are primarily naturally found in tropical and subtropical regions, although they typically infest greenhouses, and can now be found as an invasive species in a larger variety of climates.

Life History
Compared to other flies, L. trifolii have a relatively brief life cycle, ranging from 21 to 28 days in habitats they are native to. Because of this, there can be multiple generations of L. trifolii within one season. Additionally, the rate of development for L. trifolii has been shown to be temperature-dependent. Maximum pupal survival rates and oviposition rates were shown to occur at 30˚C (86˚F).

Eggs
The eggs are typically about 1 millimeter long and 0.2 millimeters wide and are oval in shape. Initially after oviposition, the eggs are clear, but they become creamy white in color as time goes on. Eggs are laid just below the surface of the leaf, so when the larva hatch, they mine their way out of the leaf as they feed, hence the name "leaf miner".

Larval Instars
The larva of L. trifolii are unique from those of many other flies in their shape, as the body of L. trifolii larva does not taper at the head end. The larva are uniform in thickness at both their anterior and posterior, but have a pair of spiracles at the posterior end. Initially, they are clear in color, but become yellow as they mature.

The larval instars are differentiable by the lengths of the body and mouthparts. The first instar is recognizable by a mean body length of 0.39 mm and a mouthpart length of 0.10 mm. For the second instar, the mean measurements are 1.00 mm (body) and 0.17 mm (mouth). For the third instar, the mean measurements are 1.99 mm (body) and 0.25 mm (mouth). The fourth instar is a non-feeding stage, and thus is usually disregarded.

Pupa
Typically, at the end of the larval phase, L. trifolii drop to the soil to pupate after exiting the leaf mines they have created. Initially, the puparium is yellow, but grows to be a darker brown over time. The puparium is typically less than 2.3 mm long and 0.75 mm wide.

Adults
Adult female L. trifolii tend to live around 13 to 18 days. Male adults typically only live 2 to 3 days because they are unable to puncture plants and thus have difficulty feeding. As previously described, both males and females are typically around 2 mm in length with a wingspan around 1.25 mm. After chewing a fan shape into the leaf of their host plant, adults feed on exuding sap of the host plant on which oviposition will occur.

Food Resources
Both larval and adult female L. trifolii feed primarily on the leaves of their host plants. Larva feed mostly on the layer of the leaf just below the epidermis, while female adults feed on liquids expelled by the leaves after the adult has punctured them. L. trifolii feed on a large variety of host plants, both vegetables and ornamental plants. Studies on the flies' preferred hosts show that some of L. trifolii 's most preferable hosts are chrysanthemums, Gerber daisies, and celery.

Oviposition
Oviposition occurs within 24 hours of mating, usually during daylight hours. When oviposition is to occur, the female punctures the host leaf in a tubular shape, feeding on the sap released from the leaf as she punctures.

Site Selection For Egg Laying
Eggs are typically oviposited on leaves toward the center of the host plant. The eggs are inserted into the tubular punctures, just below the epidermis of the host leaf. This is where the larva will create its mine upon hatching. Often times, the mother will make multiple punctures before selecting the ideal spot. Oviposition rate is significantly increased for female L. trifolii located on ideal host plants such as celery.

Parasites
The most significant natural threat to L. trifolii are parasitoid wasps.

Predators
Although predators and diseases tend to impact the L. trifolii population to an insignificant amount compared to parasitoids, both larvae and adults can still be at risk of predation by general predators. The most common predators of L. trifoli are ants.

Interactions With Humans
L. Trifolii is a highly destructive pest of both produce and ornamental plants. They often infest greenhouses and inhabit shipping containers to be exported, making them an invasive species in several countries around the globe. The spread of this pest is widely due to the flies' developed resistance to certain insecticides. This has been a major issue combatted by attempts from the Florida Fruit and Vegetable Association (FFVA) to mitigate the infestation and spread of these pests. However, due to previous spreading of L. trifolii through exported goods, L. trifolii are already a major pest of ornamentals in California. L. trifolii are most destructive to florticultural crops, as they are severly impacted by any insect damage.