Earlier this week I spent a couple of days in Philadelphia, visiting my Holy Shrine, the Orthoptera collection at the Academy of Natural Sciences. I was giving a talk at a meeting of the American Entomological Society (not to be confused with its much younger, up-and-coming offshoot, the Entomological Society of America.) It was also a great opportunity to peruse the vast holdings of African katydids at the Academy, and look for hidden gems. One of the groups of katydids that is well represented there are the Saginae, or the Predatory katydids.
These insects are the lions of the orthopteran world. All 45 currently recognized species of the Saginae are obligate predators of insects, which they catch with powerful, spiny front and middle legs. The ventral side of their thorax is also equipped with spines that help hold and disembowel their prey. Some species are sit-and-wait predators, others actively search for prey and pounce upon it. Most species are huge, and so it goes without saying that the same, spiny, muscular legs and sharp mandibles that efficiently kill even the largest insects, can do some serious damage to the fingers of a careless entomologist. Middle Eastern Saga ephippigera is considered to be the largest Palaearctic insect, and the Black-winged clonia (Clonia melanoptera) is one of the largest insects in southern Africa. The latter is also one of the loudest insects in Africa, and a single singing male can be heard from about a mile away.
Predatory katydids have an interesting, disjunct distribution. The genus Saga is found only in the western Palaearctic, from France to Jordan, and three additional genera are found in southern and eastern Africa. Their distribution can be probably explained by their preference for dry, open habitats, and they clearly avoid wet, tropical areas.
Interestingly, the European Predatory katydid (Saga pedo) is the only katydid known to be exclusively parthenogenetic. Early studies claimed that S. pedo was tatraploid (n=68), but a recent paper (Dutrillaux et al. 2009. Eur. J. Entomol. 106: 477-483) presents a more interesting scenario, proving that this insect is a pentaploid organism, with the karyotope consisting of 70 chromosomes (5n). It seems that after the first chromosomal duplication, which resulted in increasing the number of chromosomes to 4n=56 (typical Saga species have 2n=28), some already parthenogenetic females of S. pedo had a fling with a male of another, closely related species, and acquired an extra set of 14 chromosomes, bringing it up to 5n=70.
Saga pedo is also the only member of the subfamily that can be seen, albeit very rarely, in North America. Since the early 1970’s a small number of individuals have been collected and photographed in Michigan, where they probably arrived as eggs hidden in soil adhering to farm equipment imported from Italy. The last confirmed sighting is from 2009. Although I very much dislike introduced and invasive species, I must admit that if I found one of these insects in my garden I would not be terribly upset.