361 



DIPTERA. 



DIPTERACE^E. ' 



382 



cyanodon {Icono.) 



extraction and transmission of fluids ; and when these fluids are con- 

 tained within any moderately tough substance, the parts inclosed by 

 the sheath of the proboscis are used as lancets in wounding and 

 penetrating so as to allow the escape of the fluid, which by their 

 pressure is forced to ascend and enter the oesophagus. 



The palpi are situated at the base of the proboscis. The antenna? 

 are placed on the fore part of the head, and approximate at their 

 base ; they are generally small and 3-jointed ; the last joint however 

 is often furnished with an appendage called the stylet, which is con- 

 siderably diversified not only in form but in its position. 



In some of the insects of this order, the Tipulidce [TIPULID.E] for 

 instance, the antenna; are long and composed of numerous joints ; 

 and in the C'ulicidc* [CULICIDES] they resemble little plumes. 



The eyes in Dipterous Insects are generally large, especially in the 

 male sax, where they often occupy nearly the whole of the head. 



The Halteres, or Poisers, are two small organs of a slender form, 

 and furnished with a knob at their apex, situated at the base of the 

 thorax on each side, and immediately behind the attachment" of the 

 wings. These organs have been considered by many as analogous to 

 the under wings of four-winged insects. Latreille and others however 

 '>me to a different opinion, from the circumstance of their not 

 being attached to the same part of the thorax. The .use of these 

 organs is not yet ascertained ; it is however supposed by some that 

 the little knob which we mentioned is capable of being inflated with 

 air, and that they serve to balance the insect during flight, at which 

 time these organs are observed to be in rapid motion. 



As regards the thorax, it is only necessary here to observe that 

 the chief part of that which is visible from above consists of the 

 meso-thorax ; the prothorax and metathorax being comparatively 

 small. 



The scutcllutn varies considerably in form, and is sometimes armed 

 with spines ; we find it developed in an extraordinary manner in the 

 gHM^CHAM (Dalman), where it is very convex, and covers the 

 whole abdomen. 



The abdomen seldom presents more than seven distinct segments ; 

 its form is very variable. 



Dipterous Insects undergo what is termed a complete tranaforma- 

 ti'in. Their larvic are devoid of feet, and have a head of the same 

 soft substance as the body, and without determinate form. The parts 

 of the mouth exhibit two scaly pointed plates. The stigmata are 

 nearly all placed on the terminal segment of the body. When about 

 to assume the pupa state, they do not cast their skin (aa is the case 

 with the larvae of most insects), but this becomes gradually hardened, 



and after a time the animal assumes the pupa state within, so that 

 the skin of the larva forms as it were a cocoon. 



There are however exceptions to this rule, for many change their 

 skin before they assume the pupa state, and some spin cocoons. 



We may here observe, that in some of the species of the genus Sar- 

 copltaga the eggs are hatched within the body of the mother, whence 

 the insect first makes its appearance in the larva state ; and in the 

 Pupipara not only are the eggs hatched within the body of the parent, 

 but the larva; continue to reside there until their transformation into 

 pupae. 



As regards the habits of Dipterous Insects, they will be found 

 under the heads of the several families and genera ; we shall therefore 

 conclude by noticing the two great sections into which this order is 

 divided by Macquart. These are the Nemocera and the Brachocera. 



The species of these two sections are distinguished chiefly by the 

 number of joints of the antenna; and palpi. Their characters are as 

 follows : 



Section 1. Nemocera. Antenna; filiform or cetaceous, often as long 

 aa the head and thorax together, and composed of at least six joints ; 

 palpi composed of four or five joints; body generally slender and 

 elongated ; head small ; proboscis sometimes long and slender, and 

 inclosing six lancets ; sometimes short and thick, having but two 

 lancets ; thorax large and very convex ; legs long ; wings long, and 

 with elongated basal cells. 



Section 2. Brachocera. Antenna; short, composed of three joints, 

 the third joint generally furnished with a stylet ; palpi composed of 

 one or two joints ; head usually hemispherical, and as broad as the 

 thorax ; proboscis either long, sleuder, coriaceous, and protruded, or 

 short, thick, and retracted, aud containing either six, four, or two 

 lancets ; thorax moderately convex ; legs usually of moderate length ; 

 wings with the basal cells rather short. 



(Wiedemann, IHptei-a Exotica, 8vo, 1821 ; Meigen, Systematische 

 Beachreibung der bekannten Europiiischen zwe/Jtiigelingen Imekten, 

 6 vols. 8vo, with figures ; Macq uart, in the Suites a Buffon, ffistoire 

 de Iraectes, ' Diptcres,' 2 vols. 8\ r o. ; Kirby and Spence, Introduction 

 to Entomology; Walker, British M'Uteum Catalogue, 'Diptera' in 

 Intecta Britannica.) 



DIPTERA'CE^E, or DIPTEROCARPE^, Dipteradt, an important 

 order of East Indian Exogenous Polypetalous Trees. They have a 

 tubular unequal permanent calyx, with five, lobes, which after flower- 

 ing become leafy and very much enlarged, surmounting the fruit with- 

 out adhering to it. There are five petals, with a contorted {estivation, 

 an indefinite number of awl-pointed narrow anthers, and a few-celled 

 superior ovary, with two pendulous ovules in each cell ; of these all 



Diptet-ocarpits gractlis. 



l.two of the stamina; 2, a lipe fruit surrounded by the c:ih x wliosc seg- 

 ments have become laruc and leafy, and very unequal. 



