REVISION OF STREPSIPTERA PIERCE. 5 



be by osmosis or absorption only and at the expense of the vitality 

 of the host, although not fatal. Both sexes exsert the head and 

 thorax from the abdomen of the host, and the two succeeding stages 

 occur without casting the skin. 



This type of metamorphosis is unique among insects, as in no 

 other case is there complete endoparasitism. In the Meloidae and 

 Rhipiphoridse a similar hypermetamorphosis is found, in that the 

 first larvae are hexapods and the succeeding stages are progressively 

 more degenerate until the pupal stage. But these beetles are not 

 larviparous and their larval development differs as follows: The 

 meloid larvae are successively campodeoid, carabidoid, scarabaeidoid, 

 and coarctate. The strepsipterous larvae are first campodeoid, and 

 from then undergo a constant and gradual change of habitus, 

 assuming forms utterly unlike anything in the Coleoptera and more 

 resembling the straight appendageless larvae of certain Diptera. 

 The pupa resembles the vespid pupae more closely than it does the 

 coleopterous. The retention of the pupa within the larval skin is 

 paralleled in the Diptera, as well as in the Coleoptera. 



The primary character in the classification of insects is the con- 

 sideration of elytra and wings. The Strepsiptera fall with the 

 elytrophorous two-winged orders, but differ in that the elytra or 

 balancers are located more laterally and that they were never 

 expected to act as protections to the wings, for, in fact, the elytra of 

 the Tertiary genus Mengea were as rudimentary as those of existing 

 forms. The wings are inserted at a greater distance from the elytra 

 than in any of the other elytrophorous orders, and in shape resemble 

 those of the Orthoptera, being almost a quadrant of a circle, while 

 those of the Coleoptera are semicordate or semiovate. They fold 

 longitudinally as in the Orthoptera and Vespoidea, and as in 

 Macrosiagon and Myodites in the Coleoptera (Rhipiphoridae), while 

 this latter order otherwise commonly exhibits an oblique fold at 

 the base and a transverse fold in the middle or beyond. The veining 

 is very simple and radial, paralleled only by Myodites in Coleoptera. 



The mouth parts are peculiar. They are not used for feeding 

 in the adult, but may be classed with the mandibulates. Labrum 

 and labium are absent and the maxillae are reduced. The pharynx 

 exposes a broad flared surface, unprotected by any of the usual 

 coverings. The occiput remains. The mandibles are used by the 

 triungulinid to effect an entrance into the body of the host and by 

 the grown larva to cut its way through the abdominal teguments of 

 the adult host. The maxillae function possibly as sensory appendages. 



Finally, a character which has been little used, but which seems 

 to be of much value, may be used to show the wide gap separating 

 the Strepsiptera from the orders with which it has been placed. 

 It is that of the development of head and thorax and the aggluti- 



84359— Bull. 6(3—09 2 



