Vol. 3: Insects

Order: Mecoptera

Species accounts

Black-tipped hangingfly

Hylobittacus apicalis

FAMILY

Bittacidae

TAXONOMY

Bittacus apicalis Hagen, 1861, southern Illinois, United States.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

Body and appendages glossy yellow to brown. Wings clear with black tips, held outstretched when at rest.

DISTRIBUTION

Eastern United States.

HABITAT

Understory vegetation of moist, shaded woodlands.

REPRODUCTIVE BIOLOGY

The male captures or steals a prey item and emits pheromones while in flight. He offers the prey to attracted females, who reject the male or terminate copulation early if the prey is small or poor in quality. Females feed on the prey while mating, which takes 20–30 minutes. After mating, the male usually retains the prey and may use it in subsequent courtship attempts (females are not able to entirely drain the prey within the time spent in copulation). Females scatter eggs over the ground from a hanging position.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

None known.

BEHAVIOR

This species hangs from low-growing vegetation by the front legs, which are useless for walking. Movement on vegetation is accomplished through a monkey-like swinging motion. Flight is weak and undulating.

FEEDING ECOLOGY AND DIET

Adults are generalized predators, hunting small insects during the daytime. Prey is captured with the long raptorial hind legs, either from a hanging position or while flying. Draining prey of fluids may take up to one hour.

Snow scorpionfly

Boreus brumalis

FAMILY

Boreidae

TAXONOMY

Boreus brumalis Fitch, 1847, eastern New York, United States.

OTHER COMMON NAMES

None known.

Hylobittacus apicalis

Boreus brumalis

Panorpa nuptialis

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Order: Mecoptera

PHYSICAL CHARACTERISTICS

Small, dark brown, and compactly built. Males have narrow wings, about half as long as the abdomen, hooked downward and with many spines. Female wings are reduced to tiny pads.

DISTRIBUTION

Northeastern North America.

HABITAT

Larvae live inside clumps of moss growing among rocks or on loamy soil. Adults are found on rocks, soil, snow, and ice near the larval habitat.

BEHAVIOR

Adults are active in fall and winter. Activity at low temperatures is made possible by a substance in the blood that acts like antifreeze. Larvae are scarabaeiform and can be found any time of year within mosses.

FEEDING ECOLOGY AND DIET

Vol. 3: Insects

TAXONOMY

Panorpa nuptialis Gerstaecker, 1863, Texas, United States.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

Adult body is reddish brown. Wings are amber in color, with striking bands of dark brown. Larva are caterpillar-like, pale, and encircled with rings of dark spots and setae.

DISTRIBUTION

South-central United States and northern Mexico.

HABITAT

Dense vegetation in open fields and pastureland. Larvae are found beneath the soil in these habitats.

Larvae and adults feed on mosses.

REPRODUCTIVE BIOLOGY

The male leaps, grasping an appendage of the female with the claspers at the tip of his abdomen. The male then maneuvers the female onto his back and holds her in place with his hooklike wings. Copulation lasts from one to 12 hours. The female deposits eggs into moss singly or in small clutches. The life cycle probably takes two years.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

None known.

BEHAVIOR

Adults are active only during the day and rest vertically on vegetation at night.

FEEDING ECOLOGY AND DIET

Adults and larvae feed primarily on feeble or dead soft-bodied insects.

REPRODUCTIVE BIOLOGY

Males infrequently offer a salivary secretion to the female. Females lay eggs in existing cracks in the soil, probing with the ovipositor until a suitable site is found. Larvae develop in about a month. Winter is passed in the pupal stage. Adults emerge in late fall and live nearly a month. This species may have two generations per year.

	No common name	CONSERVATION STATUS
		Not threatened.
	Panorpa nuptialis
	FAMILY	SIGNIFICANCE TO HUMANS
	Panorpidae	None known.

Resources

Books

Byers, G. W. “Mecoptera.” In The Insects of Australia: A Textbook for Students and Research Workers, edited by CSIRO. 2nd edition. 2 vols. Carlton, Australia: Melbourne University Press, 1991.

—. “Order Mecoptera.” In An Introduction to the Study of Insects, edited by D. J. Borror, C. A. Triplehorn, and N. F. Johnson. 6th edition. Philadelphia: Saunders College Publishing, 1989.

Periodicals

Byers, G. W., and R. Thornhill. “Biology of the Mecoptera.”

Annual Review of Entomology 28 (1983): 203–228.

Other

Myer, John R. “Mecoptera.” June 13, 2001 [March 12, 2003].

<http://www.cals.ncsu.edu/course/ent425/compendium/

mecopt1.html>.

“The Scorpion Flies (Mecoptera).” February 25, 2003 [March 12, 2003]. <http://www.earthlife.net/insects/mecop.html>.

“World Checklist of Extant Mecoptera Species.” October 31, 1997 [March 12, 2003]. <http://www.calacademy.org/ research/entomology/mecoptera/>.

Jeffrey A. Cole, BS

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Siphonaptera

(Fleas)

Class Insecta

Order Siphonaptera

Number of families 16

Photo: Bird flea larva. (Photo by Kim Taylor. Bruce

Coleman, Inc. Reproduced by permission.)

Evolution and systematics

Fleas may have evolved as early as 140 million years ago (mya), along with their mammalian hosts. Only five flea species are known from fossil records: three from Baltic amber (35–40 mya: Palaeopsylla baltica, Palaeopsylla dissimilis, and Palaeopsylla klebsiana) and two from Dominican amber (15–20 mya: Pulex larimerius and an undescribed species of Rhopalopsyllus). The specialized combs, setae, and appendages of these relics are very similar to those of their modern relatives. Molecular and morphological data suggest the small Mecopteran family of snow scorpionflies, or (Boreidae), snow fleas is a sister group of Siphonaptera. Snow fleas are not actually fleas and are not parasitic, as are all members of the Siphonaptera.

Based on empirical evidence, some workers have divided the superfamily Pulicoidea into two subfamilies (Pulicinae and Tunginae), whereas others have considered them as two separate families (Pulicidae and Tungidae). DNA analyses conducted from 2000 to 2003 of taxa assigned to these subfamilies indicate that they are two distinct families. The family placement of many of the 244 genera remains to be defined by molecular studies. Until molecular studies redefine the genetic phylogeny, 16 families belonging to five superfamilies are recognized: Ceratophylloidea (Ancistropsyllidae, Ceratophyllidae, Ischnopsyllidae, Leptopsyllidae, and Xiphiopsyllidae), Hystrichopsylloidea (Chimaeropsyllidae, Coptopsyllidae, Ctenophthalmidae, Hystrichopsyllidae, Pygiopsyllidae, and Stephanocircidae), Malacopsylloidea (Malacopsyllidae

and Rhopalopsyllidae), Pulicoidea (Pulicidae and Tungidae), and Vermipsylloidea (Vermipsyllidae). Of about 2,575 species (including subspecies), some 5% occur on birds, while the remaining 95% parasitize mammals. DNA analyses indicate that fleas originated on mammals, with some crossing over later to avian hosts. Fleas typically do not parasitize amphibians and reptiles.

Physical characteristics

Fleas are wingless, laterally compressed, holometabolous insects, and the adults are adapted to a parasitic mode of life. Their eggs are small, elongated spheres, varying in color from pearly white to dark brown to black; they are about 0.02–0.06 in (0.5–1.4 mm) in diameter. Larvae are wormlike and range from 0.02 to 0.4 in (0.5–10 mm) in length, with well-sclerotized head capsules, three thoracic segments without appendages, and ten abdominal segments. There usually are three larval stadia (intervals between molts), although some species of Tunga have only two. A silk pupal case contains an exarate (having the appendages not “glued” to the body) pupa that is 0.008–0.4 (0.2–10 mm) long. Fine debris, which blends with the surroundings, often adheres to the pupal case.

In general, adult fleas range from 0.04 to 0.3 in (1.0–8 mm), excluding engorged Tungidae and Vermipsyllidae. Female adult fleas typically are larger than males, and those of

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Female (left) and male dog fleas (Ctenocephalides canis). (Photo by Kim Taylor. Bruce Coleman, Inc. Reproduced by permission.)

a few species may achieve lengths of 0.6 in (16 mm) when they are engorged or gravid. Their mouthparts are modified for piercing avian or mammalian hosts and sucking their blood. Adults have evolved highly modified combs and setae on their body and legs. These features provide protection for intersegmental membranes and spiracle openings and are used for grasping hairs and feathers and for preventing dislodgment during the host’s preening activities. Legs are specialized to promote mobility through the fur and feathers of the host and for jumping to facilitate host acquisition. Fleas that have adapted to a parasitic life on birds (bird fleas) tend to have more setae that are longer and more slender than those of fleas that parasitize mammals (mammal fleas).

The internal anatomy of fleas may be as important in flea phylogeny as the external morphological features. Females possess either one or two spermathecae. Two are considered a primitive condition, because a blind duct exists in most species with a single spermatheca. Most families have six rectal pads, a proventriculus with spines, and a ventral nerve cord. Tungidae are exceptional in possessing only two rectal pads and no proventricular spines; moreover, the nerve cord is displaced dorsally. The variety of morphological specialization (such as head, thoracic, and abdominal combs; the degree of scleroti-

zation of the exoskeleton; the length and number of setae; the development of mouthparts, tarsal claws, and associated bristles on appendages; spiracle characteristics; development of complex genitalia, particularly in males; diversification of internal anatomy; and display of neosomatic growth) is reflective of the corresponding diversity of the respective host species.

Male and female fleas are sexually dimorphic. In addition to size differences, the eighth sternum, ninth tergum, and aedeagus of males are highly specialized, whereas only the seventh sternum of females is particularly modified. The dorsal area of the male head frequently is grooved longitudinally, and the anterior portion of the head is divided from the posterior portion by a distinct suture or groove. The female head may or may not be divided. Antennae generally are longer in males than in females.

Distribution

The Ceratophyllidae, Hystrichopsyllidae, Leptopsyllidae, Vermipsyllidae, Coptopsyllidae, and Ancistropsyllidae occur predominantly in the boreal continents of North America, Europe, or Asia. Those families restricted to the southern continents of Africa, Antarctica, Australia, or South America

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include Malacopsyllidae, Rhopalopsyllidae, Stephanocircidae, Pygiopsyllidae, Xiphiopsyllidae, and Chimaeropsyllidae. The remaining three families, Ctenophthalmidae, Ischnopsyllidae and Pulicidae, occur in both the Northern and Southern Hemispheres.

Habitat

Fleas parasitize hosts in virtually every conceivable terrestrial habitat, adapting to the microclimate of the nests, burrows, and body conditions. Such adaptations enable fleas to live in the most extreme environmental conditions. For example, Glaciopsyllus antarcticus occurs only in the frigid, subzero conditions of the Antarctic. They proliferate in the microclimate of the nest and in the down of their avian host, the southern fulmar (Fulmarus glacialoides). Many species (Xenopsylla and Nosopsyllus) thrive in the dry conditions of deserts, living in the burrows of their rodent hosts, where the temperature and humidity are optimal for their development. Adult fleas are found on mammalian hosts more frequently and in greater numbers than those species parasitizing birds. Fleas have adapted only to birds that use their nests over and over (swallows, seabirds, and some ground-dwelling birds and cavity dwellers). A few species (Pulex and Ctenocephalides), especially those inhabiting coastal, semitropical, and tropical regions, are free living, jumping on and off their hosts and proliferating in open environmental conditions, such as floors of homes, pathways, barnyards, animal pens, and pet beds.

Behavior

Perpetuation of each species is dependent on the success of finding a host. Some fleas remain in a quiescent pupal state for an extended time, to survive cold periods or to wait until a host approaches. Vibrations produced by an approaching host may stimulate adults to emerge immediately from their pupal cases. Although the visual acuity of fleas is poor, shadows of approaching hosts illicit a jump response. They also are attracted to the warmth and carbon dioxide emitted by potential hosts. A few species, particularly bat fleas, are negatively geotrophic (moving against gravity), crawling up cave walls to locate bats roosting on the cave ceiling.

Feeding ecology and diet

With the exception of Uropsylla tasmanica, the larvae of most fleas are free living, scavenging on dried blood, animal dandruff, and animal excreta in the host’s nest or the environment. Larval cat fleas (Ctenocephalides felis felis) feed on partially digested blood excreted from the anus of adult fleas. The larvae of Hoplopsyllus, Tunga, and Dasypsyllus are documented facultative ectoparasites, feeding either on host tissues or on organic debris in the nest substrate. Uropsylla tasmanica larvae burrow into the skin of their host and are the only known true obligate larval flea parasites. A few species are predaceous on other nest-dwelling organisms.

Depending on the species, adult fleas ingest blood by either tapping into a capillary, or by cutting the tissue and caus-

Order: Siphonaptera

A gray squirrel flea (Orchopeas howardi) among squirrel fur. (Photo by Kim Taylor. Bruce Coleman, Inc. Reproduced by permission.)

ing a pool of blood from which to feed. A few species have been observed to imbibe water. The vast majority of fleas are intermittent feeders, among them, C. f. felis, and some attach to their hosts permanently, for example, Echidnophaga gallinacea and species of Tunga. The nutritional requirements of adults are understood only partly. Male and female fleas require a blood meal as a prerequisite for spermatogenesis or oogenesis. Females feed more rapidly than males and require larger volumes of blood to facilitate egg production. The chemistry of host blood is known to affect the host specificity of some species and is suspected to influence many others.

Reproductive biology

Males assume a position directly beneath the female, each facing the same direction. The occipital groove in the dorsal portion of the male head frequently is developed to accommodate the keel-shaped surface of forward sternites of the female abdomen. The male clasps the sides of the female sternites with suckerlike structures on the inner surface of the antennae. He also may clasp the hind legs of the female between a notch in the hind coxa and the retracted femur. The highly modified ninth tergite (basimere and telomere) attaches to the terminal segments of the female in a “clasping” manner. The posterior margin of the seventh sternum of many females is modified with various lobes and sinuses that facilitate attachment during copulation. The vaginal canal also is modified to accommodate partial insertion of the highly modified apical portion of the aedeagus. Sperm transfer is accomplished during insertion of long penis rods through the vaginal canal, into the bursa copulatrix, through the duct of the spermatheca, and into the spermatheca. This process varies from species to species.

Copulation is vastly different in Tunga. The female attaches to the skin of the host and soon becomes enveloped by

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the host tissues, exposing only the caudal disc (the last four abdominal spiracles, the anus, and the vaginal opening). A darkly sclerotic ring made up of host tissues surrounds the caudal disc. Males locate the female and copulate in situ with a highly modified aedeagal apparatus. After copulation, the female develops massive numbers of eggs that are expelled into the environment wherever the host travels. The breeding cycles of Cediopsylla and Spilopsyllus are bound to the estrus cycle of their hosts, hares and rabbits. Other genera probably are influenced by the breeding cycle of the host, but studies are lacking.

Neosomy is the expansion of pregenital abdominal segments by secretion of new cuticle without molting. This process takes place in females of Hectopsylla, Neotunga, Tunga

(Tungidae), Chaetopsylla, Dorcadia, Vermipsylla (Vermipsyllidae), and Malacopsylla (Malacopsyllidae), as a way to accommodate growth up to 1,000x normal size. Neosomatic growth is especially pronounced in Tunga, Neotunga, and Dorcadia. Males do not undergo neosomatic growth, because their principal function is to mate. Females expand primarily to accomodate egg production.

Some species lay eggs on their host, others do so indiscriminately in the environment, and still others place them in the lair or nest of the host. The duration of each stage of the life cycle varies for each species. An example is the common cat flea C. f. felis. Eggs are laid on the host within 48 hours of a blood meal. The eggs drop to the ground (most often in the lair of a cat or dog), hatch, and pass through three larval stadia. The mature larva spins a silken cocoon and molts within, ultimately emerging as an adult. The developmental cycle is completed in two to three weeks under optimal conditions of temperature and humidity but may take as long as

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three to four months. Across the order, sex ratios are approximately 1:1, and longevity of adults may range from only a few weeks to more than three years.

Conservation status

There are no flea taxa specifically listed as threatened by the IUCN; however, species that are very host specific (that is, they depend on a single host for their existence) are in danger of perishing if their host is endangered. Attempts to identify such combinations have never been undertaken.

Significance to humans

The bite of the dog, cat, and human flea (Pulex complex) may cause annoyance, irritation, extreme itching, hypersensitivity, and secondary infections. Many species of flea transmit diseases to humans and their pets directly through their bite, through rubbing or scratching infected feces into an open wound, or by ingesting infected fleas. These include plague (Yersinia pestis), murine typhus (Rickettsia typhi), and cat scratch fever (Bartonella henslae). Fleas also have the potential to transmit Q-fever (Coxiella burnetti), tularemia (Francisella tularensis), listeriosis (Listeria monocytogenes), salmonellosis (Salmonella species), and Carrion’s disease (Bartonella bacilliformis). Fleas also are efficient vectors of myxomatosis, a viral disease of rabbits. Some serve as the intermediate host of the double-pored tapeworm (Dipylidium caninum) of humans and several tapeworms of sylvatic (wild) and commensal rodents (Hymenolepis diminuta and H. nana). The filarial worm, Dipetalonema reconditum, and the protozoan blood parasite, Trypanosoma lewisi, may be transmitted to dogs and rats, respectively.

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2

1

3

4

5

1. Chigoe (Tunga penetrans); 2. Bat flea (Ischnopsyllus octactenus); 3. Sheep and goat flea (Dorcadia ioffi); 4. Oriental rat flea (Xenopsylla cheopis cheopis); 5. Helmet flea (Stephanocircus dasyuri). (Illustration by Bruce Worden)

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