Owlflies (Neuroptera: Ascalaphidae)

The Ascalaphidae (owlflies) are a family of neuropteran, easily recognisable by their dragonfly-like appearance, sometimes colourfully-patterned wings, and large eyes. Most of the ~430 species (in ~65 genera) live in subtropical to tropical biomes, in dry, high-altitude habitats.

As the compilation above, taken and modified with highlights from Winterton et al., 2010), shows, they have always been considered as sisters to the Myrmeleontidae (antlions); Winterton et al. (2010)’s analysis also finds the same result. One look at the larva of an antlion and of an owlfly will show the striking resemblance. In general, this type of larva is typical for what is termed the myrmeleontiform suborder, which also includes the Psychopsidae, Nemopteridae and Nymphidae; however, it must be said that the characters that set this group of families apart from the other neuropterans have to do with the adult genitals and the head of the larvae (Aspöck et al., 2001), not the outer morphology of the larvae.

The sister-group relationship of the Myrmeleontidae and Ascalaphidae is confirmed by a single autapomorphy, the fusion of the tibia and tarsus of the larval hind legs (character 57, Beutel et al., 2010).

The easy way to distinguish a myrmeleontid and an ascalaphid is to look at the antennae: ascalaphid adults have short, clubbed antennae. If you only have larvae, check out the habitat: ascalaphid larvae tend to live in mossy places, while myrmelontid larvae inhabit sandy areas – but this might only apply to European species, I haven’t observed them elsewhere.

There are three subfamilies of ascalphid: the Ascalphinae, Haplogleniinae and Albardiinae.

The Ablbardiinae is a monospecific subfamily, i.e. it contains only one species from Brazil that I can’t tell you much about, unfortunately.

The Ascalphinae and Haplogleniinae are separated by their eyes: ascalaphines have eyes divided along the middle, while haplogleniines don’t (Aspöck et al., 2001). It must be said that this hasn’t been tested cladistically, and without a rigorous analysis, I hesitate to elevate the divided eyes to the status of an apomorphy.

All ascalaphid adult eyes are superposition eyes, very sensitive to light but with a low resolution, as is typical for nocturnal insects; only in Eurasia are some ascalaphids active during the day.

They have a simple life cycle: the female lays a mass of eggs on grass or twigs. After hatching, the larvae congregate (perhaps as a defence mechanism, as with zebras), before individually wandering to live alone, exhibiting complex behaviour such as camouflaging themselves with soil, as Henry (1977) showed (compare this with the pit-digging behaviour of myrmeleontid larvae!). They are vicious predators, injecting a paralysing venom into their prey and eating them while still alive.

The winged adults are quite agile, and are also predators, hunting in open grasslands and forests.

As for their fossil record, they’re pretty rare: a total of 8 species are known, ranging from the earliest representative in the Late Jurassic/Early Cretaceous of China (dating of formation still uncertain), through various European and Russian Oligocene compression fossils, to three species in the Dominican and Baltic amber. The amber fossils include larvae as well as adults, which isn’t surprising given the habitat of the larvae on plants.

References:

Aspöck U, Plant JD & Nemeschkal HL. 2001. Cladistic analysis of Neuroptera and their systematic position within Neuropterida (Insecta: Holometabola: Neuropterida: Neuroptera). Systematic Entomology 26, 73-86.

Beutel RG, Friedrich F & Aspöck U. 2010. The larval head of Nevrorthidae and the phylogeny of Neuroptera (Insecta). Zoological Journal of the Linnean Society 158, 533-562.

Henry CS. 1977. The Behavior and Life Histories of Two North American Ascalaphids. Annals of the Entomological Society of America 70, 179-195.

Winterton SL, Hardy NB & Wiegmann BM. 2010. On wings of lace: phylogeny and Bayesian divergence time estimates of Neuropterida (Insecta) based on morphological and molecular data. Systematic Entomology 35, 349-378.

Leave a Reply