10 BULLETIN 66. UNITED STATES NATIONAL MUSEUM. 



The very recent description by Dr. Filippo Silvestri of a female 

 hypermetamorphic insect known as Rhyzostylops inquirendus, adds 

 one more genus to those closely similar forms. This female has legs 

 winch are very simple in structure, is provided with short, simple 

 antennae, and lacks all but two pair of mouth parts, the pharynx 

 being exposed, due to the absence of labrum and labium. There are 

 no rudiments of wings; the abdomen is 10-jointed. The insect was 

 found dead under shale or "tufa" at the side of its cluster of eggs. 

 From the eggs, triungulinids were obtained. These had two tarsal 

 claws and posteriorly were armed with stylets. In only two instances 

 are there any resemblances to the Strepsiptera; namely, the rudi- 

 mentary mouth parts of the adult and the possession of anal stylets 

 by the triungulinid. The insect is anomalous and may or may not 

 belong in the Rhipiphoridae. If it does, it forms a new tribe below 

 the Rhipidiini. The larva forms a new step in the series of first 

 larvae by having two tarsal claws. 



In all coleopterous classifications containing the Stylopidae they are 

 arranged at the end of the Heteromera. As LeConte and Horn 

 (1883) are the best authorities in the English language on the Cole- 

 optera, the fallacy of thus locating the Strepsiptera may best be 

 illustrated from their work. In subdividing the Coleoptera they 

 define Isomera as "having the hind tarsi with the same number of 

 joints at least as the others," and Heteromera as having the "front 

 and middle tarsi 5-, hind tarsi 4-jointed." They place Stylopidae 

 with Heteromera, while they obviously would have to fall in Isomera 

 if they belonged in the Coleoptera. It must be remembered that 

 the Strepsiptera present four types of isomerous tarsi. The sole 

 reason they had for placing the group in Heteromera was to place 

 them at the end of a series of parasites with somewhat similar meta- 

 morphosis and other parallel characters as Saunders, Schaum, and 

 Lacordaire had done. 



Since the Strepsiptera are isomerous and the Rhipiphoridae are 

 heteromerous, it is evident that they belong to distinct lines of descent, 

 which has been pointed out as probable. Being separated thus from 

 the Rhipiphoridae there is no coleopterous group with winch they 

 can possibly be allied. 



In conclusion, then, the writer would place the Strepsiptera as a 

 separate order, on a distinct line of descent from that of the Coleop- 

 tera, and nearer the Hymenoptera and Diptera, and as highly special- 

 ized as the highest insects in any of the orders. 



The thoracic structure places the order near these other two 

 because of the great development of the metathorax and the extreme 

 reduction of the prothorax and mesothorax. It differs by having 

 the parts not agglutinate except in the female and immature stages. 



