* 1 Adult
* 1.1 Head
* 1.2 Thorax
* 1.2.1 Taxonomically important bristles on the thorax
* 1.3 The wings
* 1.3.1 Taxonomically important wing venation terms
* 1.4 Abdomen
* 2 Larva * 3 Pupa * 4 References and further Reading * 5 External links
Schematic of Muscoid
I: head ; II: thorax ; III: abdomen .
1: prescutum ; 2: anterior stigma ; 3: scutum ; 4: basicosta ; 5: calyptra ; 6: scutellum ; 7: alary nerve (costa) ; 8: ala ; 9: urite ; 10: haltere ; 11: posterior stigma ; 12: femora ; 13: tibia ; 14: spur ; 15: tarsus ; 16: propleura ; 17: prosternum ; 18: mesopleura ; 19: mesosternum ; 20: metapleura ; 21: metasternum ; 22: compound eye ; 23: arista ; 24: antenna ; 25: maxillary palpi ; 26: labrum (inferiore) ; 27: labellum ; 28: pseudotrachae ; 29: tip.
Adults are small (< 2mm.) to medium sized insects (- < 10mm.), larger
The head is distinct from the thorax, with a marked narrowing at the
neck. In "lower flies" (
Brachycera:Calliphoridae head.Hypognathous (mouth ventral) *
Dexia rustica showing precise arrangement of bristles.
In the "higher"
The eyes are usually very obvious, but reach a remarkable development in the Brachycera. In this suborder the eyes are markedly convex and have grown to occupy most of the side of the head. The space between the two eyes can sometimes be reduced to a narrow strip running from the front of the occipital region, or disappear altogether because of the direct contact between the eyes or their margins. The morphology of the compound eye is characterized by a significant number of ommatidia, of the order of thousands in Muscoids. The ocelli, when present, are located in the top of the head, arranged at the corners of a triangle in an area called stemmaticum or ocellar triangle. Schematic representation of the morphology of a muscoid dipteran 1: labellum; 2: lower lip (labium), 3: maxillary palp, 4: upper lip (labrum); 5: subgenal area; 6: clypeus; 7: fronto-orbital area; 8: fronto-orbital bristles; 9: outer vertical bristle; 10: inner vertical bristle; 11: postocellar bristles (postvertical bristles in old literature); 12: ocelli; 13: ocellar bristles; 14: compound eye; 15: Frontal suture or ptilinal suture; 16: antenna; 17: arista; 18: vibrissa.
For the purpose of systematics the presence, the arrangement and the conformation of the cephalic bristles is important and they have a specific terminology. Bristles on the head are: frontal bristles sometimes named lower orbital bristles are located on the frontal plates of the frons resembling a small alley extending from the base of the antennae toward the vertex and edging the median frontal stripe laterally. Sometimes they are situated lower, along the frontalia below the antennal attachment and over a greater or lesser distance. Orbital bristles are located on the vertex plates of the frons and usually restricted to its upper half. They may be arranged in longitudinal rows named inner and outerorbital bristles. (The frontal and vertex plates of the frons can be visualised on the basis of the arrangement of the frontal and orbital bristles); ocellar bristles are located on the vertex between the ocelli; outer and inner vertical bristles are located on the border between the vertex and the occiput and near the upper corner of the eyes; postvertical bristles are located behind the ocelli on the occiput near the median line of the head; vibrissae usually arrayed in small numbers along the facial sections of the arcuate suture, near the margin of the oral cavity; sometimes they ascend along the suture over a greater or lesser distance, occasionally almost to the place of antenna1 attachment; false vibrissae-bristles are placed along the margin of the oral cavity.
Sometimes the terminology is conflicting. For instance in the
Acalyptratae there are usually two bristles, more or less strong,
positioned along the posterior margin of the ocellar triangle. These
bristles are called "postvertical bristles" in old literature, since
the nineteenth century, and the term is used sometimes in the recent
literature. Steyskal (1976) proposed the name "postocellar bristle"
the adopted term in the Manual of Nearctic
The antennae are divided into two basic morphological types that are
the basis of the distinction between the two suborders and their
denomination. In Nematocera, they are pluriarticulate, threadlike or
of feathery type, composed of 7-15 undifferentiated items. In
The mouthparts show, according to the systematic group, a variety of conformations. Mouthparts are modified and combined into a sucking proboscis, which is highly variable in structure. The ancestral condition is the piercing and sucking type proboscis, more modified proboscis forms variously rasp or sponge fluids. Some species have non-functional adult mouthparts. No flies bite in the sense of cutting food.
Nematocera:Culicidae head.Feathery filamentous antennae, piercing suction mouth parts *
Brachycera:Muscoidea. Antenna with arista *
Brachycera:Muscoidea. Sucking mouthparts
1: mesoprescutum; 2: humeral callus; 3: notopleuron; 4: mesoscutum; 5: posterior callus; 6: mesoscutellum; 7: tansverse suture trasversa; 8: postscutellum; 9: metanotum; 10: wingbase; 11: mesopleuro-tergite o laterotergite o katatergite; 12: haltere ; 13: stigma; 14: metapleuron; 15: metacoxa; 16: hypopleuron o meron; 17: mesocoxa; 18: epimeral suture; 19: mesoepimeron o anepimeron; 20: ventral mesoepisternum o katepisterno; 21: suture episterno-precoxale; 22: procoxa; 23: pleural suture; 24: dorsal mesoepisternum o anepisterno; 25: propleuron.
McAlpine terminology versus other terminology.Equivalents are:- postpronotum = humeral callus or humerus;anepisternum = mesopleuron;proepisternum = propleuron;proepimeron = no equivalent;anepimeron = pteropleuron;katepisternum = sternopleuron;katepimeron = no equivalent;meron = hypopleuron; greater ampulla = no equivalent;laterotergite = no equivalent;mediotergite = no equivalent;postpronotum = humeral callus or humerus;anepisternum = mesopleuron;proepisternum = propleuron;proepimeron = no equivalent;anepimeron = pteropleuron;katepisternum = sternopleuron;katepimeron = no equivalent;meron = hypopleuron;greater ampulla = no equivalent; laterotergite = no equivalent;mediotergite = no equivalent
Taxonomically Important Bristles On The Thorax
* ACROSTICAL (A) bristles adjacent to the median longitudinal axis of the scutum. They may be irregular or align in two or more rows.The number of rows, the number of setae in each row, the size and the thickness are significant . In many groups, the acrostichal setae are replaced by setulae or hairs. * PRESCUTELLAR ('psc) two acrostical bristles, more developed than the other acrosticals, inserted in front of the scutoscutellar suture. * DORSOCENTRAL (DC) these bristles are aligned along two rows adjacent to and outside the acrostichals. * POSTHUMERAL (PH) bristles aligned in the presutural area and parallel to the suture which separates the scutum from the humeral calli. * HUMERAL (HM) sometomes called postpronotal bristles are on the humeral calli. * PRESUTURAL (PS) * NOTOPLEURAL (NP) bristles on the notopleuron * INTRALAR (postsutural)(IA) more or less regularly aligned bristles near the dorsocentral series. The position is not well defined. * SUPRALAR (postsutural) (SA) these setae are limited in number, and located from the prealar callus to the supralar area. * POSTALAR (PA) limited in number, they are located on the postalar callus near the lateral margin of the scutum behind the insertion of the wing. * SCUTELLAR (psct) bristles on the scutellum. They may be marginal or on the dorsal side of the scutellum (called the disc).
The chaetotaxy of the pleura is also of taxonomic significance.The characters taken into consideration are presence or absence, the number, and the position of setae and groups of hairs on the
* anepisternum or mesopleuron - anepisternal or mesopleural bristles * katepisternum or sternopleuron - katepisternal or sternopleural bristles * proepisternum and proepimeron - proepisternal and proepimeral bristles, or propleural bristles * anepimeron (pteropleuron) - anepimeral or pteropleural bristles. * meron (hypopleuron) - meral or hypopleural bristles.
The fundamental peculiarity of the
The level of specialization—anatomical, functional and morphological—is such that in general these insects fly, often exceptionally, well, with particular reference to agility. All Diptera are equipped with only one pair of functional wings, which are on the mesothorax (front). The wings on the metathorax are transformed into the halteres or rocker arms. From this characteristic comes the name of the order, from the Greek dipteros, which means "two wings". In consequence of this morphological structure, the mesothorax represents the segment of greater development and complexity, while the prothorax and metathorax are considerably reduced.
The halteres are club-shaped organs, used to balance the insect in
flight, consisting of a proximal portion connected to a
mechano-sensory organ. The homology between the wings and halteres is
demonstrated by the four-winged mutant of the fruit fly Drosophila
melanogaster. The development of the halteres varies according to the
systematic group: in the
The mesothoracic wing is entirely membranous, completely transparent
and colourless, or bearing zonal pigmentation useful for recognition.
Its surface is divided into three regions: the most developed is the
alar (main flight) region, supported by robust wing veins; posteriorly
is the anal region; and, finally, in the rear section-proximal, there
is an expanded lobiform alula.The alula also termed the axillary lobe
is a broad lobe at the proximal posterior margin of the wing stalk. It
is continuous with the upper calypter and distally it is (usually)
separated from the wing by an indentation called the alular incision.
Aluli are a newly acquired feature of the
The system of venation is simplified but is representative of the
Comstock–Needham system , which was conceived in the late nineteenth
century to define precisely the terminology of the wing morphology of
Taxonomically Important Wing Venation Terms
* COSTA (C), the SUBCOSTA (SC), the RADIUS (R), the MEDIA (M), the
CUBITUS (CU), and the ANAL VEIN (A).There has been much disagreement
concerning the homologies of the veins posterior to the subcosta in
The most encountered terms used in
* CELL CUP.Also called the posterior cubital cell and often called
the anal cell.The form of the cell cup is an important character.
* COSTAL BREAK. These frequently occur especially in the
Schizophora.They are weakenings of the costa and are one to three in
number. Normally these breaks are located proximal to the insertion of
the subcosta.The most frequently occurring break is just proximal to
where the subcosta joins the costa or an imagined point where it would
join the costa if complete. A similar break, which occurs almost as
frequently, is located slightly distal to the humeral crossvein
(crossvein h).The third,far less frequent, break, is found slightly
proximal to crossvein h marking off a short, thickened, heavily
bristled section at the base of the costa (the costagium of
Séguy).The breaks are named the costagial, humeral HB, and subcostal
breaks SB. Costal breaks are rare in the
The scutellum is nearly always distinct, but much smaller than (and immediately posterior to) the mesoscutum. The scutellum macrochaetae are important in taxonomy.
* Radial forks diagram Limoniidae:
Cylindrotoma wing veins:
Tabanidae wing veins
Phytomyzinae wing veins *
Phoridae wing veins (reduced venation) *
Cecidomyiinae wing veins (reduced venation)
The relatively thin legs have precisely arranged bristles which also function in chaetotaxy.The femora and tibia may bear combinations of dorsal, anterodorsal, posterodorsal, ventral, anteroventral and posteroventral bristles. The position, number, size and inclination of these bristles is important in the taxonomy of higher flies. The leg flexes (tibia on femur) in the dorsal ventral plane.The dorsum of the tibia (especially) and the femur is often identified by a double line of very small bristles. Another important bristle is the preapical on the tibia (presence or absence is important at family level)
The morphology of the abdomen is substantially determined by morphoanatomic adaptation, in both sexes, as a function of the reproduction. In general, the 10 urites (one of the segments of the abdomen or post-abdomen) are reduced to a lower number of urites because of structural modifications of the first urite and the last. Typically there is atrophying of the first urite and the merging of 2 ° and 3 ° urotergites. Tergites and sternites can be well distinguished from each other, but often there is a differential development, with the tergites overlapping the sternites; the extreme case is when the expansions of tergite ventrally merge, forming a tube structure or ring. In females, the last urites become thinner and stretch forming a flexible telescopic ovipositor. This morphological adaptation is often accompanied by sclerotisation of the terminal eighth urite, so that the ovipositor is able to penetrate through the tissues of the organism which will accommodate the eggs and larvae. In the male, the last urites undergo a complex transformation to form a device, integrated with the genitalia called the hypopygium. The degree and nature of structural change varies according to the systematic group, but usually involves the development of the lobes of the ninth urotergite into forceps (epandrium) and IX urosterno (hypandrium). There is sometimes a twist along the axis of the abdomen, resulting in reversal of the positions of the epandrium and the hypandrium.
Abdomen of Sarcophaga carnaria *
Abdomen of Calliphora *
Male genitala Afridigalia adrianponti
Most of the larvae of
Culex restuans larva *
Muscidae larva (microcephalic) *
Stratiomyidae larva *
Orthocladiinae head *
Cephalo-pharyngeal apparatus *
Eristalis larva with respiratory siphon
Depending on the number and position of the tracheal spiracles, the following types of breathing apparatus can be distinguished.
* apneustic, with absence of stigmas (spiracles * metapneustic, with only one pair of stigmata.These are on the abdomen. * amphipneustic, with two pairs of stigmas. On pair on the prothorax, one pair on the abdomen. * holopneustic, with two pairs of thoracic stigmas and eight abdominal pairs.
The most frequent type,found in the generality of Brachycera, is
amphipneustic, while other types appear mostly in aquatic larvae. The
The pupae of
Obtect pupae are generally free and unprotected, with the exception
of those of
In the last phase of their lives, the pupae of
Obtect pupa of
REFERENCES AND FURTHER READING
This article is largely based on a translation of the Italian page on Ditteri.
* Brown, B.V., Borkent, A., Cumming, J.M., Wood, D.M., Woodley, N.E., and Zumbado, M. (Editors) 2009 Manual of Central American Diptera. Volume 1 NRC Research Press, Ottawa ISBN 978-0-660-19833-0 * Capinera, John L. (Ed.), 2008 Encyclopedia of Entomology Springer Verlag. ISBN 978-1-4020-6242-1 . * Colless, D.H. an illustrated key for identifying the orders and families of many of the immature insects with suggestions for collecting, rearing and studying them, by H. F. Chu. Pictured key nature series Dubuque, Iowa,W. C. Brown Co.Full text online here