738 



CLASS IV. LNSECTA. 



the whole time being spent in a feverish search for mates. As a 

 rule but one Stylops, or at most two or three, live in one host, 

 but they are extraordinarily prolific. Ten specimens of Xenos 

 have however been found in the body of the wasp Polistes. 

 Some observers maintain that parthenogenesis is met with in 

 this Order, but the matter requires renewed investigation. 



Fam. 1. Stylopidae. With the characters of the Order. Stylops, 

 Xenos. 



Order 21. DIPTERA.* 



Only one pair of wings, the mesothoracic, present ; these are 

 membranous ; the hind-wings are represented by a pair of 

 knobbed processes, the halteres ; the thoracic segments are much 

 fused ; mouth parts piercing and sucking., variable. Metamor- 



3 v 



FIG. 471. Mouth parts and head of Anopheles maculipennis, magnified (after !Nuttal and 

 Shipley). 1 antennae ; 2 clypeus ; 3 labrum and epipharynx ; 4 mandible ; 5 first maxilla ; 

 6 hypopharynx ; 7 labium ; 8 maxillary palps. 



phosis very complete. Larva usually a maggot, always without 

 thoracic legs, and frequently with a minute, retractile head. Pupa 

 either exposed with appendages more or less adherent to the body, 

 or enclosed in a tough capsule and with appendages not adherent. 



* Becher, Wien. Ent. Zeit., i, 1882, p. 49. Brauer, Verh. Ges. Wien, xl, 

 1890, p. 273. Loew, Smithson. Misc. Coll. vi, 1862. Brauer, DenTc. Ak. 

 Wien., xlii, 1880, p. 105. Williston, Manual of North American Diptera, 

 1896. Schiner, Fauna Austriaca, Diptera, 1860. Verrall, British Flies, 

 London, in course of publication. F. V. Theobald, Monograph of Culicidae, 

 Brit. Museum, 1907. Id., Account of British Flies, London, 1891-2, Pts. 

 1-5. 



