y8 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



In reviewing the clasping arrangement in the Hymenoptera, two 

 principal types, forming the two ends of a pretty continuous series 

 of transitional forms, can be distinguished. The first of these 

 types is found in the Tenthredinidae, Ichneumonidae, and Formicidae ; 

 the second in the Anthophilidse and Vespidas. The Tenthredinidae 

 (pi. ix_, fig. 19), Ichneumonidae (pi. ix, fig. 20), and Formicidae 

 (pi. ix, fig. 21) have very flat, rather short, and only slightly 

 bent hooks, at their bases delicate pointed spines (lacking in the 

 Formicidae), a widely open groove, furnished with slender spines 

 on the outside (also lacking in the Formicidae), no longitudinal 

 ridge, and (as a rule wanting in the Tenthredinidae) generally 

 sparse, short marginal bristles. The clasping apparatus of the 

 Tenthredinidae is elastic and not very firm ; in the Ichneumonidae 

 and Formicidae it corresponds to the type described in the An- 

 thophilids, but, in consequence of the thinness of the wall of the 

 costal vein, it lacks the firmness peculiar to this family. Character- 

 istic for the Anthophilidae and Vespidas (pi. ix, figs. 22-26) is the 

 presence of well-developed, firm, long, and well bent distal hooks, 

 numerous, stout, blunt spines at the bases of the hooks, and usually 

 a longitudinal ridge on the outer side of the always deep groove, 

 as well as long marginal bristles standing in closely crowded groups. 

 Here the clasping apparatus is remarkably firm. On the whole, 

 the clasping apparatus of the Anthophilids and Vespidae is firmer 

 than that of the Tenthredinidae, Ichneumonidae, and Formacidae. 

 and the question arises whether a correspondingly higher demand is 

 made upon it in the former than in the latter families. The resist- 

 ance of the air to the firmly joined wings principally depends upon 

 the rapidity of the movement of the wings, i. e. } the number of 

 wing-strokes executed per second and the length of the wings. Ac- 

 cording to the investigations of Marey (1886, p. 126), the bumble- 

 bee makes 240, the bee 190, the wasp no wing-strokes per sec- 

 ond. No such data are available for the Tenthredinidae, Ichneu- 

 monidae, and Formicidae. It is, however, possible to judge of the 

 number of wing-strokes by the pitch of the tone produced by them 

 in flight. Of course, no absolute data can be obtained in this 

 manner, for errors will always creep in, caused, in accordance with 

 Doppler's principle, by the raising of the tone when the insect ap- 

 proaches and its lowering when it retreats, the mingling of the tone 

 of flight with the voice proper, etc. But these errors are not such 

 as to preclude the possibility of deducing approximately the differ- 

 ences of the number of wing-strokes per second from the differences 



