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Moth of the Week
Hornet Moth
Sesia apiformis
The hornet moth is a part of the family Sesiidae or the family of clearwing moths. They get their common name predictably from how they mimic the appearance of the hornet. This type of mimicry is called Batesian mimicry, which is when a harmless species mimics the appearance of a unpalatable or defended species to protect themselves from predators. It was first described in 1759 by Carl Alexander Clerck under the name Sphinx apiformis.
Description This moth uses what called Batesian mimicry to resemble the hornet so predators do not want to eat it for fear of being stung. The adult moths have clear wings with yellow and striped black bodies. The number of stripes varies, females have two stripes while males have three. They are about the size of a hornet with the same jerky flight pattern when disturbed. The only difference is the hornet moth has more yellow and lacks the waist between the abdomen and the thorax.
Wingspan Range: 34 - 50 mm (≈1.34 - 1.97 in)
Females are larger than males
Diet and Habitat The larvae eat several species of poplar trees such as apsen (Populus tremula), black poplar (Populus nigra), and goat willow (Salix caprea). They prefer trees surrounded by heavy vegetation as those kinds show more evidence of infestation from larvae burrowing into trees. Adults do not eat.
This moth ranges over mainland Europe, Great Britain, and parts of the Middle East. It had also been introduced to America and Canada. They prefer open habitats such as parks, hedgerows, golf courses, quarries, fens, pond edges, and pits.
Mating The female moths attract males using special posterior glands to emit pheromones, usually soon after emergence. The male doesn’t seem to have any courtship behaviors as the two sexes are likely to begin mating as soon as they come into contact. Both males and females mate multiple times with different partners before the female beings laying her eggs.
Females prefer to lay eggs on old or isolated trees surrounded by vegetation. Females can lay from hundreds to thousands of eggs and exhibits no parental care. When comparing the number of eggs laid to the number of adults emerging per year, it is clear the large number of eggs laid is to make up for the large mortality rate between the egg and adult stages.
Predators This species of moth is primarily preyed on by magpies and great tits. Interestingly, these birds do not eat hornets despite eating this moth. An explanation for this is since these birds don’t eat hornets, the mimicry is less effective as they have any bad experiences with insects of this coloration. In fact, it can be suggested that the black and yellow coloration has the opposite effect: once the birds realize this moth is harmless and can be easily seen, they begin to actively seek them out.
Fun Fact The hornet moth is seen as a pest in the eastern United Kingdom due to a large dieback of poplar trees from larvae burrowing into them. However this dieback is not inherently caused by the larvae but instead from drought and human influences, which the larvae increase the effect of.
(Source: Wikipedia, Butterfly Conservation)
Moth of the Week
Red-Belted Clearwing
Synanthedon myopaeformis
Image Source
The red-belted clearwing is a part of the family Sesiidae. It was first described in 1789 by Moritz Balthasar Borkhausen as Sphinx myopaeformis. This was later changed to Synanthedon myopaeformis. This moth is called the red-belted clearwing in Europe, the apple clearwing moth in North America, and the apple borer. This is due to their tendency to damage their host apple trees. It is considered a pest in Europe.
They may be confused with the large red-belted clearwing and the red-tipped clearwing.
Description This moth has a thin, dark blue, segmented body. The body is hairless aside from a bushy tail at the end of the abdomen. They are noticeable due to a bright red-orange band on one of the segments of the abdomen. The wings are clear with a dark outline and veins and a fringe on the outer margin (outer edge). The wings help distinguish the red-belted clearwing from the large red-belted and red-tipped clearwings as the wings have no red-orange markings.
Wingspan Range: 1.8 - 2.8 cm (≈0.71 - 1.1 in)
Diet and Habitat This species eats mainly apple, specifically Crab Apple (Malus sylvestris), as well as Pear (Pryus communis), Hawthorn (Crateagus monogyna), Almond (Prunus dulcis), Rowan (Sorbus aucuparia), apricots, cherries, mountain ash, peaches, plums, and quince. In Canada, adult moths have been attracted to the flowers of the snowy milkweed.
They can be found natively in Europe, North Africa, and Asia Minor. This species was noticed to North America and first detected in Canada in 2005. They inhabit well established orchards and gardens, hedgerows, open woodland, and mature scrub.
Mating Adults emerge from their cocoons in early summer and on flight from May to August, this is presumably their mating season. Females can lay up to 250 eggs, usually singly in the cracks or damaged areas of the trunk and branches they are hosting in. Females attract males with pheromones released from glands. A 2010 study found that 3,13-octadecadienyl acetate is the primary sex hormone.
Predators The larvae of this moth are preyed on by parasites, fungi, and bacteria. The main parasite of red-belted clearwing larvae is Liotryphan crassiseta. Other parasites are Nematodes, Steinernema sp. The fungi Beauveria bassiana and Metarhizium brunneum are common causes of death in larvae as well as the bacteria Bacillus thuringiensis.
Fun Fact
The adult red-belted clearwings are significantly less active on cold days compared to warm days.
In 2014, Judd and Eby found that S. myopaeformis does not discriminate between yellow, green and white or between purple, blue, red, and black. This suggests that they are dichromatic, meaning they can perceive mainly two colors. This affected traps set to catch this species as they acted differently depending on the light reflected.
As this species is considered a pest to apple trees, people have attempted to control the population. This has been tried with pheromone/mating disruption, pheromone laced traps, other chemical traps, the use of predators/enemies, and the covering of apple tree trunks in oil.
(Source: Wikipedia [1][2][3], Butterfly Conservation, Michigan State University)