420 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



greater than the mesothorax. The greatest reduction of Coleopterous thorax 

 occurs on the mesothorax (see pi. 69, fig. 4). The greatest reduction of 

 Strepsipterous thorax occurs on the prothorax. 

 b. The prothorax never consists of more than a tiny ring, but it is often 

 crowded far forward into the head until the pleurae are reduced to 

 mere intersegmental skin. 

 c. The mesothorax is a little larger than prothorax, witli several small 

 pieces, all separated by intersegmental skin. There is no strength 

 in this segment. 

 d. The seat of bodily power is entirely in the metathorax, which em- 

 braces over half the body. 

 e. The head is separated from the thorax, and each segment of the 

 thorax from the others by intersegmental skins; furthermore the 

 various pieces of the prothorax and mesothorax are likewise 

 separated. In addition to this longitudinal freedom of movement 

 there is also great vertical freedom imparted to the body by the 

 intersegmental areas of the pleural region. Such a bodily forma- 

 tion is very primitive among insects, occurring otherwise only 

 in the lower orders of hemimetabolous insects. It indicates a 

 very different line of descent from all the other holo-metamorphic 

 orders. 

 / The metathorax displays several remarkable characteristics. The 

 praescutum migrates from a position as a depressed neck to a po- 

 position in the braced part of the segment and pushes backward 

 breaking the scutum and reducing the scutellum. The scutum 

 also shows a tendency to divide to form the parascutellum and 

 in the extreme modification is separated from it by interseg- 

 mental skin. The postscutellum is the predominant piece in 

 the entire body, being as large as all the rest of the thorax. 

 No other insect known has the postscutellum thus enlarged, and 

 it alone is sufficient to absolutely identify a Strepsipteron. At 

 the base of the postscutellum is an area known as postlumbium. 

 which in the more primitive groups is intersegmental, but 

 which becomes in some genera a chitinized piece. 

 ff. The metathorax of the Strepsiptera is far more divided than 

 the metathorsx of any other order. 

 h. The front wings are reduced to inflated balancers, which 

 rapidly vibrate and assist in the making of noise. They 

 have the rudiments of wing veins. 

 i. The hind wings are membranous, longitudinally fohling 

 with only radial veins. The axillary cord is not attached 

 directly to the scutellum, which is quite distant from the 

 base of the wing, but to a small detached piece located on 

 the epimeral area. The number of veins varies from 

 eight to five. 

 j. The pro- and meso-coxae are free and small, the meta- 

 coxae are larger and more broadly attached. The pro- 

 and meso-trochanters are very long, the meta-trochan- 

 ters are shorter. The femora and tibiae display no 

 unusual characters. The tarsi are isomerous, typically 

 five-jointed with claws, but progressively reduced to 

 four, three and two joints without claws. 



