The Poplar hawk-moth, Laothoe populi is a widespread and predominantly European type of hawkmoth. As the name implies, it is associated with poplar (Populus sp) which is its preferred host plant. It is one of the non-feeding types of hawkmoths (Smerinthinae) that are short lived because of their lack of functional mouthparts. Laothoe populi is often found in suburban areas such as parks, gardens but also forests, swamps and heathland.
Depending on the geographical location and local climate, it has one to three generations a year. Northern populations have only one generation, whereas Southern populations have two or rarely in very warm years up to three. This is likely due to natural key factors such as daylength and temperature regulating the induction of diapause in pupae (overwintering). They will have as many generations as the local climate allows before they overwinter. Females are less active than the males. Females of Laothoe populi females don’t like to fly excessively. They appear quite apathic and inactive and may sit in the same spot for a longer time, waiting for a male to arrive.
The females can emit pheromone, a chemical that attracts males. The job of the female is mainly to remain undiscovered and in a secure position, until a male finds her. Because females carry hundreds of eggs and are greater in size, flying is harder for them due to their increased bodymass. At night, males are very active and actively patrol the area to detect females. However, after pairing, females become more active and start to lay eggs – these eggs hatch in 5 to 14 days time depending on the temperature. Laothoe populi has been recorded to mainly feed on Salix (willow) and Populus (poplar), but will accept several types of them and caterpillars are found on a wide variety of poplar and willow species.
Genus Laothoe can be distinguished from other similar hawkmoths by the scalloped wing edges and the unusual resting position where the hindwings are placed higher than the forewings. The caterpillars are green but variable; they vary from lime green to mint green to blueish green. They can have yellowish ‘warts’ that cover their bodies. Some forms have very noticable bright red dots – these spots help camouflage them in sick Populus trees that are infected with kinds of leaf-spot fungus such as (Marssonina sp.) that often affects poplar and makes their leaves appear spotted. Fully grown caterpillars descend to the floor and burrow in the soil to pupate underground. Sometimes they pupate in crevices at the base of the host tree.
The females are bigger than the males and have fatter abdomens. Males tend to curve their abdomens upwards if resting, and also have thicker antennae than the females. The moth is mostly brown to grey with a lot of colour variation; some of them can be rusty brown while others appear lighter and more sand coloured.
- Difficulty rating: Average (Not hard)
- Rearing difficulty: 6/10 (From egg to pupa)
- Pairing difficulty: 3/10 (Archieving copulations)
- Host plants: Salix (willow), Populus (cottonwood)
- Natural range: Nearly all countries in Europe, Turkey, European Russia + Ukraine, Ural, Altai and Siberia, Caucasus region, northwest China
- Polyphagous: Yes
- Generations: Multivoltine – depending on the geographical location and local climate, it has one to three generations a year. Northern populations have only one generation, whereas Southern populations have two or rarely in very warm years up to three. This is likely due to natural key factors such as daylength and temperature regulating the induction of diapause in pupae (overwintering).
- Family: Sphingidae (hawkmoths)
- Pupation: Subterranean (burrows in soil)
- Prefered climate: Temperate, Palearctic
- Special notes: Larvae need a lot of fresh air and ventilation
- Wingspan: 60mm – 110mm
- Binomial name: Laothoe populi (Linnaeus, 1758)
After pairing, the female will produce a lot of pale, transparent yellow/greenish oval shaped eggs and stick them to rough surfaces. Depending on the size and vitality of the female, they lay around 50 to 200 eggs. These will hatch in roughly 5 to 14 days, temperature affects their development – warmer temperatures speed them up. The hatchlings are pale, green/whiteish but turn darker green as they start feeding from the leaves. They have a tiny anal horn.
After the first instar, the caterpillars develop white/yellowish stripes. Cricket tubs, plastic containers (tupperware) and other similar types of boxes are suitable for rearing them.
In captivity, from the third instar and beyond, the caterpillars require a lot of airflow. Do not keep them in plastic boxes until their final stage, or they will most probably die; ventilation is key. They can be placed in rearing sleeved, net cages, or plastic tubs with the lid removed. The best is to raise them on a cut branch of the host plant in a bottle of water; especially Populus will remain fresh for a longer time that way, allowing the larvae to feed undisturbed for a few days.
The caterpillars of Laothoe populi can be fully grown in 1 to 2 months time, mainly depending on the temperature and quality of their food plants. When they are ready to pupate, caterpillars descend from their host plants to the floor in order to burrow in the soil or in crevices around their host trees. Here they pupate in a subterranean chamber. The pupal stage is the overwintering stage in Laothoe populi, and pupae can remain dormant until the following spring. In captivity they can be overwintered in a basement, a garden shed, or simply outside in a well-isolated plastic box.
If not overwintering, the adults can emerge from their pupae in about a month. Males curve their abdomens upward, are smaller and have thicker antennae than females. Females have fat, round abdomens. Each female can lay over a 100 of eggs. The moths pair easily in captivity, if confined in small cages made of netting as to provide proper airflow and ventilation. The moths are quite variable and can be seen in many shades of grey to brown. They do not have a functioning proboscis and cannot feed.
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