And the answer is: Margarodidae

Margarodidae cf Margarodes: male dorsal habitus

I guess no one wins a heap of points for this one, but Greg Z. comes the closest with “something in the Coccoidea”. On Alberta Bugs, where I posted the url, Felix, Chris, Amanda, and Sylvia all also came to Coccoidea. Congratulations to all of them and five points to each (one to Ted for Hexapoda and one to Adrian for his comment on the eyes). I did better with the specimen in hand and Borror, De Long & Triplehorn – Margarodidae. It helps that I recognized it as probably a scale insect male too, and so did not have to attempt the order key. After that the compound eyes (rare in scales), one-segmented tarsi with single claw, and 10-segmented antennae got me to one of the 11 families (~8000 known species) of Coccoidea – Margarodidae.

That id was one-step beyond my level of expertise, but the internet and the generosity of the small community of margarodid aficionados came to the rescue. Penny Gullan at the Australian National University was first back with the confirmation that the animal did resemble Margarodidae sensu stricto – a Ground Pearl – and apparently the first record of the family for Canada! Bob Foottit at Agriculture and Agri-Food Canada agreed and his colleagues at the USDA backed him up. Chris Hodgson at the National Museum of Wales also agreed, but couldn’t be sure of the genus. Chris also explained that from what little is known about flying male scale insects, the body tends to be held more or less vertically – so the ‘ventral’ compound eyes are probably more oriented frontally in flight. Imre Foldi at the Muséum national d’Histoire naturelle in Paris and Yair Ben-Dov at The Volcani Center in Israel also agreed on Margarodidae s.s. and tentatively suggested that this animal is may be the undescribed male of a species of Margarodes. So, starting from a small white dish of soapy water in southern Alberta, this luckless male (or at least its image) has journeyed around a good chunk of the World.

Ground Pearls are so called because the spherical cysts formed by the immature feeding stage(s) on the roots of their hosts may be pearl-like in appearance (and up to ~4 mm in diameter). Although many if not most margarodids may go about their business without us even knowing they are there, some species are economically important and damage sugar cane in Australia, grape vines in South Africa and South America, and turf grasses in the southern United States (Allsopp et al. 2000, Unruh & Gullan 2007). For example, the Centipede Ground Pearl Dimargarodes meridionalis (Morrison) feeds on the roots of grapes and grasses (especially Centipede Grass Eremochloa ophiuroides) in the southern United States (Camarino 2009, Unruh & Gullen 2007).

As is often the case, most of what is known about margarodids comes from the study of the pest species. Their life cycle (the following discussion is based mostly on Foldi 2005) is almost as strange as their morphology. Eggs laid in a waxy ovisac in soil near a host plant hatch into a crawler stage with functional legs, antennae, and piercing-sucking mouthparts. The crawler finds and attaches to a host plant (usually on a root). As they feed both waxy filaments and blobs of liquid excrement are produced and develop into a protective test. As feeding continues, the insect becomes globular, and with enough imagination, pearl-like. The first moult results in an apodous blob (legs and antennae reduced to vestiges) attached to the plant by its feeding tube. The cyst (the blob-like insect and its protective test) continues to grow. The feeding cyst is also the overwintering stage and apparently may last for many years if conditions are inappropriate for forming adults. Some margarodids are asexual (partheongenetic) and only produce females. At the adult moult the female regains short legs and antennae, but lacks mouthparts and cannot feed. Parthenogenetic females may remain within the test and produce eggs or look for a new host. In the bisexual species, the female digs her way to the surface using her hook-like fossorial front legs (and may climb up onto vegetation) to emit a pheromone plume. Males also develop from cysts (see Fig. 2 in Foldi 2005), but pass through a prepupal stage with legs and antennae, an exarate pupa, and finally moult into a winged male that digs to the surface and takes wing to find females. With no mouthparts in either sex, I guess the adults have but one thing on their minds: after mating, the female returns underground and produces a waxy ovisac to protect her body and eggs of which she may lay 100 or more.

Nine ground pearl species are known to occur in North America, mostly in the more southern states of the US from Florida to California. However, Eumargarodes laingi Jakubski, 1950 (=Margarodes dactyloides McDaniel, 1966), the pest of sugar cane in Queensland, also feeds on the roots of Buffalo Grass (Bouteloua dactyloides) at least as far north as Scotland, Texas (just south of Oklahoma) (Unruh & Gullen 2007). Buffalo Grass reaches its northernmost distribution in central Montana and western Saskatchewan – not far from the much collected from Onefour Heritage Rangeland Site, the mixed grass prairie from hence our wandering male – but Buffalo Grass is not reported in the Flora of Alberta. Also, males of Eumargarodes laingi (the only species in the genus) are unknown (Samson & Harris 1998) and at least the Australian populations are parthenogenetic. Another possible contender, Heteromargodes americanus Jakubski, is known from the roots of grasses in northern Wyoming and a male collected from a wind vane trap in Hansen, Idaho, has been doubtfully attributed to this species (Hodgson & Foldi 2006). However, this male has compound eyes that meet ventrally and differs in details of the sclerites and robustness of the legs, and so is not likely our species. Thus, we have Canada’s first known Margarodidae – possibly a species of Margarodes, but most likely not described, and host unknown. Something tells me I may be spending some time digging in the mixed grass prairie in southern Alberta next summer.

References

Allsopp PG, McGill NG, Stringer JK. 2000. Host-plant resistance in sugarcane to pink ground pearls, Eumargarodes laingi Jakubski (Hemiptera: Margarodidae): Confirmation and further screening of clones. Australian Journal of Entomology 39: 316-321.

Camarino A. 2009. Ground Pearls, Earth Pearls, Pearl Scale, Margarodes spp. (Insecta: Hemiptera: Margarodidae). http://edis.ifas.ufl.edu/in554

Foate KD. 2002. Entomologists swarm to Onefour.

Foldi I. 2005 . Ground pearls: a generic revision of the Margarodidae sensu stricto (Hemiptera: Sternorrhyncha: Coccoidea). Ann. Soc. entomol. Fr., 2005, 41 (1) : 81-125.

Hodgson C & I Foldi. 2006. A review of the Margarodidae sensu Morrison (Hemiptera: Coccoidea) and some related taxa based on the morphology of adult males. Zootaxa 1263: 1–250.

Samson PR & WJ Harris. 1998. Seasonal phenology and distribution in soil in sugarcane fields of the pink ground pearl, Eumargarodes laingi Jakubski, with notes on Promargarodes spp. (Hemiptera: Margarodidae). Australian Journal of Entomology 37: 130-136.

Unruh CM & PJ Gullan. 2007. Hypogeal margarodids of the genus Heteromargarodes Jakubski (Hemiptera: Margarodidae) from the western United States. Proc. Entomol. Soc. Wash. 109 (1): 166-181.

USDA Margarodidae 

3 Responses to “And the answer is: Margarodidae”

  1. Gary Anweiler Says:

    Boy, it is even weirder out there than I thought! But I shall continue sleeping soundly knowing that thing is not the size of a groundsquirrel.

    Gary

  2. Ted C. MacRae Says:

    I think I’ll have to add this to Strepsiptera on the list of small, quirky insects that I really hope to see one day!

  3. BioBob Says:

    Thanks for the great story !

    Insects can be so strange, intricate and curious.

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