122 ARTHROPOD A. 



The fecundity and rapid succession of generations of many 

 species cause them to appear sometimes in immense quantities ; 

 the progeny of the blowfly is said to amount to 500 millions in 

 twelve months. Agamic reproduction occurs in some species ; 

 the larva of Miastor metraloas has been found to contain other 

 larvas identical in all respects, except in size, with the enveloping 

 larva ; and these larvae continue to produce successive generations 

 which ultimately develop into perfect inseots. 



In the Pupipara the larva changes into the pupa in the abdo- 

 men of the mother; in all other Diptera eggs, or larvae just re- 

 leased from the egg, are produced. The larvae, known as maggots, 

 are apodal, or very rarely with rudimentary legs. In the blow- 

 fly " not one structure exists as it exists in, the maggot " (Lowne). 

 The mouth is generally provided with tv^o hooks, which " are 

 thrust into the substance from which the larv* derive their nu- 

 triment." The pupa, in the majority of Diptera, is merely the 

 larva with a hardened case [pupas coarctatae] ; in the remainder 

 the pupa is in a separate case, having its limbs enclosed in 

 distinct sheaths [pupae obtectae]. The pupae of the Culicidae are 

 locomotive. 



The species are very numerous ; about 9000 are found in 

 Europe ; Schiner thinks that they are not a twentieth part of 

 those inhabiting the whole world. Among them are the gnat 

 (Cukx pipiens), musquito (Culex, sp. variaa), Hessian fly (Ceci- 

 domyia destructor), gad-fly ( Tabanus bovinus), fly (Mttsca domes- 

 tica), blue-bottle (Musca Ccesar), blow -fly (Musca vomitoria), 

 flesh-fly (Sarcophaga carnaria), tzetze (G-lossina morsitans), 

 cheese-hopper (Piophila casei), bot-fly of the sheep ((Estrus 

 ovis), bot-fly of the horse (Gastrus equi\ bot-fly of the bullock 

 (Hypoforma bovis), spider-fly, forest-fly or bot (Hippobosca 

 equina), sheep-tick (Melophagus ovinus), and fLea,(Pulex irritans). 

 Sand-flies are a general name ; some are referable to Simulium. 



The Diptera are divided into four sections or suborders ; but 

 the last is aberrant, and is by some ranked as an order. Brauer 

 has divided them according as the pupa-case opens longitudinally 

 (Orthorhapha) or curvilinearly (Cyclorhapha). 



Thorax distinct from the abdomen. 

 Larva developed from the egg. 



Antennae many-jointed NEMOCERA. 



Antennas three-jointed BRACHYCEKA. 



Larva and pupa developed in the body of the 



mother PUPIPARA. 



Thorax confounded with the abdomen .. .. APHANIPTERA. 



