Saturday, November 26, 2011

A Week for the Bugs: Part I – It’s all in the beak

Very young bugs with thrips, their close relatives

Last week I did something that has become unusual for me: I went to an Entomological Society of America Annual Meeting (its 59th). Yes, I was one of about four thousand bug-obsessed people who descended on Reno, Nevada, for 5 days of presentations on the current state of entomological research in North America (and the World). One bug or another was the buzz for each and every of the 2,200 presentations from entomologists from all over the United States and three dozen other countries. Well, bugs in the common sense, anyway.
A stink bug deploys its all important beak
When I was a child, defining a bug was simple: if it scurried on spiny legs and wasn’t a spider, it was a bug. Such logic sufficed for a child, but as I grew older and began my indoctrination into the entomological mysteries, I learned that there were ‘bugs’ for the common people and ‘true bugs’ for scientists. 
A lightening 'bug' is actually a beetle (Ellychnia corrusca)
 The Heteroptera Latreille, 1810, then an order of about 40,000 species of insects, contains the 'true bugs’. As adults, most heteropterans have ‘different wings’, that is the front pair are hardened and thickened (except towards the tips) and the rear pair are larger and translucent. Heteropterans also have their mouthparts formed into a beak or proboscis for piercing and sucking the juices of insects, plants, or even people.
A seed bug Peritrechus fraternus
The true bugs of my youth included the always creepily interesting assassin bugs and ambush bugs. Then there were the pesky plant bugs, lace bugs, leaf-footed bugs, seed bugs, and the smelly and foul-tasting stink bugs. A trip to a pond or stream revealed armies of water bugs, usually going by other names such as toe-nippers, backswimmers, waterboatmen, and water striders. 
Bug eats bug - note membranous hind wings of victim
 Perhaps the most infamous of true bugs are the bed bugs (family Cimicidae). Along the road to becoming blood-sucking parasites, an ancestor of the bed bugs lost its wings, but otherwise they are typical bugs. Well, so they said, but I never saw one until I was much older. Along the road to becoming a university professor, I lost the Heteroptera as an order, but I gained a world where bed bugs are now common.
Two bed bugs from Queensland with beaks deployed
Heteroptera was good enough to get me through university, and as a suborder sustains me still, but science moves on and today’s true bugs now include the Homoptera (‘same wing’) of my youth. What was once Homoptera have a host of common names. Aphids, plant lice, whiteflies, mealybugs, and scale insects are familiar to anyone who has tried to grow a plant. And then there are the noisy cicadas (aka locusts); bizarre lanternflies; and far too numerous hoppers (plant-, leaf-, tree-, and frog-) and spittlebugs. 
Meet the bugs in spittlebug
 I suppose, 'spittlebug' should now be two words, ‘spittle bug’, at least for those who feel that common names must follow the current scientific wisdom. All bugs with similar piercing-sucking mouthparts, irrespective of their common names, are now subsumed in the older ordinal name Hemiptera (‘half wings’) of Linnaeus, 1758.
A 'throat beak' leafhopper Colladonus belli (Uhler, 1877)
The Homoptera is well and truly gone (see Gullan 1999) and has been replaced by two tongue-twisters. Auchenorrhyncha is, I assume, from the Greek for ‘throat beak’ and referring to an anterior origin of the proboscis. This includes the 42,000 or so species of cicadas, laternflies, and assorted hoppers and spittle bugs.
'Breast-beaked' Giant Lupine Aphids (with thrips)
 The Sternorrhyncha or ‘breast beaks’ have a more posterior proboscis as in the 15,000 or so species of aphids, plant lice, and their scaly, mealy and whitefly relatives. Don’t get too attached to these names, though, because scientific progress may shatter them as well. Some day, a grouchy old throat-beak lover may be bemoaning the Auchenorrhyncha of his youth.
Water strider, currently secure in suborder Heteroptera
Gullan, PJ (1999). "Why the taxon Homoptera does not exist". Entomologica 33: 101–104.

Sunday, November 6, 2011

How to Know a Fly, Part II: Fruit, Pomace, Names & Patterned Wings

Drosophila 'fruit fly' or 'dew fly'?

Tiny flies with red eyes hover over many a bowl of fruit. I suppose that is why we call them fruit flies, but therein reigns imprecision, confusion, and bad wine. I suppose the most well known fruit fly must be Drosophila melanogaster Meigen, 1830, because it inhabits biology and genetics textbooks the world over. My translations of the genus and species names are ‘dew lover’ and ‘black belly’, neither exactly fruity, but seemingly in agreement with other translations. Carl Fredrik Fallén proposed the name Drosophila in 1823 with Musca funebris Fabricius, 1787, as the type species. Funebris is Latin for funeral or death. That would seem to leave us with the equally fruitless ‘Death’s Dew-Lover’ as the type species of the type genus of the 'fruit fly' family Drosophilidae. No wonder, many entomologists, especially if they work in horticulture or quarantine, use ‘Fruit Fly’ for another family: the Tephritidae.
Adult Apple Maggot - a real Fruit Fly (Tephritidae)
Admittedly, although the Tephritidae does contain many economically important pests of fruit, the name may be derived from the Greek for ashes or ash-coloured. Species of Tephritis Griffith & Pidgeon, 1832, do not occur in the Home Bug Garden, but another tephritid fly in the same tribe and with similar habits and similar looks does: Campiglossa albiceps (Loew, 1873). Like species of Tephritis, the maggots of this fly inhabit the 'flowers' (actually heads of many small florets) of plants in the Asteraceae (asters, daisies, goldenrod etc.) and eat the seeds (achenes), but to a botanist achenes are the fruits, so we have some consistency.
Campiglossa albiceps - a tephritid Fruit Fly of ashy mien?
No joy for the etymologist with Tephritidae, but I’m not the only one to find the conjunction of ‘fruit fly’ and Drosophila objectionable. The eminent geneticist MM Green (2002) has a delightful rant in the journal Genetics on the diversity of habitats infested by drosophilid ‘fruit flies’. Perhaps the only thing that ties together the ecology of most species of Drosophila is a fondness for rotten things. Green points out that ‘Pomace Fly’ was the preferred common name in 20th Century genetics texts until the Roaring Twenties when ‘Vinegar Fly’ and the infamous ‘Fruit Fly’ started slugging it out.
Scaptomyza sp. a drosophilid 'fruit fly' that breeds in rotting leaves
As anyone who has allowed Drosophila to get into his or her fermenting mash might know, Vinegar Fly is an all too appropriate name: Drosophila carry the microbes that compete with wine yeasts. Pomice, the mush leftover after fruit hs been juiced, also makes a nice base for a common name. For most of the flies in the family Drosophilidae whose larval habits are known, it is the rot in the fruit  that makes their habitat. The maggots tend to feed on the yeasts and bacteria that develop (probably after having been introduced by adult flies) in spoiled or damage leaves, fruit, nuts, cacti, sap fluxes, mushrooms, and similarly liquefying plant substrates. Perhaps Fallén knew what he was writing about.
Leucophenga sp. a drosophilid 'fruit fly' associated with mushrooms
But even if Fallén was trying to make his name reflect the behaviour of his species, why should we care? Common names are not for scientists. Besides, generalizing about the habits of a family of insects, or even a genus, is likely to lead to error. There are drosophilid maggots that eat fresh water algae, hang out in the gills of land crabs, live in flowers, mine leaves or stems, and even one or two species that attack fresh fruit. Evolution tends towards the opportunistic and if the right opportunity presents itself an insect is likely to try and take it on. An example of opportunism is the drosophilid Chymomyza amoena (Loew, 1862) – a gift from North America to Europe. This fly breeds in a variety of fallen fruit, acorns, and nuts in Eastern North America and is now spreading through apple and chestnut orchards in Europe. Apparently, there are no European ‘fruit flies’ that fill this niche, and our native is happy to oblige (see Burla 1997, Band et al. 2005, Matteson et al. 2007 in references below).
Chymomyza ('juice fly') from AB that breeds in wounds on aspen trunks
The only Chymomyza I’ve seen in Alberta lacks the patterned wings (or boldly contrasting legs – see Eberhard 2002 in refs below) that are used for sexual signaling in both drosophilid and tephritid (and many other) flies and prefers oozing sap to fruit. However, we do have our ‘true’ Fruit Fly: the Apple Maggot (aka Railroad Worm – presumably from the winding trail of the maggot in the fruit) Rhagoletis pomonella (Walsh, 1867) to entertain us. This fly appears to have originated in North America as a maggot in the fruit of hawthorns (genus Crataegus). Like apples, to which they are related, hawthorns have attractive white flowers in the spring (the White Hawthorn is the state flower of Missouri) and red fruit that somewhat resemble tiny apples. When apples started to outnumber hawthorns, some hawthorn flies switched hosts to give us our Apple Maggot. Although watching one strut around in one's garden is not a good sign, they are far more interesting than the cabbage maggots that wreck the broccoli, turnips, and radish.
Rhagoletis pomonella - not a welcome guest, but an attractive one
Well, enough is enough. As usual, what I thought would be a simple post on a few interesting ‘fruit flies’ that might take an hour or so has led to a weekend’s worth of ‘free time’ lost to reading about bugs (instead of doing chores). And I haven’t even gotten to the really interesting things like the ability of some Chymomyza species to survive freezing to −100 °C  (see Koštála et al. 2011) or their use in exploring the ‘Timeless’ gene. I guess there are worse ways to waste one’s time, but just now I’m informed it is time for dinner and I’d better get cooking.
Campiglossa albiceps - a true fruit fly that eats flowers
Band HT. 1995. A note on the sympatric collection of Chymomyza (Diptera: Drosophilidae) in
Virginia's Allegheny Mountains. Great Lakes Entomologist 28(3-4): 217-220.

Band HT; Bachli G; Band RN. 2005. Behavioral constancy for interspecies dependency enables Nearctic Chymomyza amoena (Loew) (Diptera : Drosophilidae) to spread in orchards and forests in Central and Southern Europe. Biological Invasions 7(3): 509-530 DOI: 10.1007/s10530-004-6352-2

Band HT, Band RN & Bachli G. 2003. Nearctic Chymomyza amoena (Loew) is breeding in parasitized chestnuts and domestic apples in Northern Italy and is widespread in Austria. Mitteilungen der Schweizerischen Entomologischen Gesellschaft 76(3-4):307-318.

Burla, Hans. 1997. Natural breeding sites of Chymomyza species (Diptera, Drosophilidae) in Switzerland. Part II. Mitteilungen der Schweizerischen Entomologischen Gesellschaft 70(1-2): 35-41.

Eberhard William G. 2002. Natural history and behavior of Chymomyza mycopelates and C. exophthalma (Diptera: Drosophilidae), and allometry of structures used as signals, weapons, and spore collectors. Canadian Entomologist 134(5):667-687.

Green MM. 2002. It Really Is Not a Fruit Fly. Genetics 162:1-3.

Grimaldi, DA. 1990. A phylogenetic, revised classification of genera in the Drosophilidae (Diptera). Bulletin of the American Museum of Natural History 197: 1–128.

Vladimír Koštála , Helena Zahradníčkováa,& Petr Šimeka. 2011. Hyperprolinemic larvae of the drosophilid fly, Chymomyza costata, survive cryopreservation in liquid nitrogen. PNAS 108(32): 13041–13046.

William Mattson, Henri Vanhanen, Timo Veteli, Sanna Sivonen & Pekka Niemela. 2007. Few immigrant phytophagous insects on woody plants in Europe: legacy of the European crucible? Biological Invasions 9:957–974 DOI 10.1007/s10530-007-9096-y