Order 1. Entozooid Flies—Diptera.
3519. All the thoracic rings coalesced, and along with them the first or basi-abdominal ring, unto which are attached the halteres or balancers; only the two posterior wings present; the labium prolonged into a proboscis, which incloses the setiform maxillæ. Larvæ apodal and white.
The Diptera resemble the Entozoa in a striking manner through their apodal, soft and white larvæ, and even through their habitation, which is mostly in fetid and moist animal matters. Added to this, they respire usually through two tubes which open upon the anus.
Many during their metamorphosis do not shed their skin; but it becomes, during the pupa condition, only horny, representing a small case, whose bottom springs up in front like an operculum, and gives exit to the perfect Fly which has been therein developed.
Upon the first abdominal ring of the imago two nodose pedicles stand out, which are called halteres; they are probably the old respiratory tubes.
The maxillæ have changed into bristles, which act like pestels within the groove-shaped labium, puncture and pump in the fluid.
They divide into three families like the White-blooded Worms, or according to the orders of their cohort.
Fam. 1. Typical Diptera, Schmeissen.
Antennæ triarticulate, the last joint being mostly spatulate and furnished with a lateral awn or bristle; only two suctorial setæ inclosed between the terminal valves of a fleshy proboscis, which admits of being retracted within a large cephalic or oral cavity. The Muscidæ, unto whom the Common House-flies belong, and also the Hippoboscidæ or Louse-flies. It is my opinion too, that the Fleas also are to be ranged among the Diptera.
Alliance 1. Klappenmucken. The two punctuating setæ placed between two valves without a proboscis—Flea (Pulex) and Louse-fly (Hippobosca.)