HYMENOPTKRA. 



11 



same species ; the wing-system alone, therefore, appears to form 

 distinctive and satisfactory divisions of this remarkable family of 

 Ilymenoptera. 



The immense variety of form observable in the apterous fe- 

 males of this genus renders it impossible to found any generic 

 divisions upon such pecuharities. The relative proportions of the 

 head, thorax, and abdomen vary greatly, the former being some- 

 times wider than the thorax, sometimes of the same width, and 

 frequently narrower. The thorax is oblong-quadrate, narrowed 

 anteriorly into a neck, or deeply strangulated in the middle, with 

 various intermediate gradations. The abdomen, although usually 

 wider than the head and thorax, is sometimes of the same \yidth. 



The very great dissimilarity existing between the winged 

 males and the apterous females renders it a matter of impossi- 

 bihty to unite the sexes of a species with a certainty of correct- 

 ness, without a positive observation of the living insects ; but 

 much has been done in this respect by Robert Bakewell, Esq., for 

 some years resident in Australia, whose collection has been most 

 liberally placed at my disposal for examination, and from which 

 many new species have been presented to the Museum Col- 

 lection. 



Species of Australia. 

 I. Thynnus dentatus. 



Thvnnus dentatus, Fabr. Syst. Ent. p. 360. 1 S ; Ent. Syst. ii. 

 iM4. 1; Syst. Pie^. p. 231. 1. 



Latr. Gen. Or. et Ins. iv. pi. 3. f. 1, & torn. i. t. 13. f. 2, 3, 



4 c? ; Encycl. Meth. p. 382. f. 8. 

 Giier. Voy. Coq. Zool. ii. 222. 

 King, Berl. Abhandl. (1842) 15. 1. 

 Don. Ins. New Roll. pi. 41. f. 1. 

 Reenter, Gen. Ins. t. 35. f. 8. 

 Lamarck, Anim. sans Vert. t. 4. f. 109. 



Hab. Australia. 



The Fabrician description of this species is not suiBciently 

 minute in structural details to distinguish the insect amongst 

 the multitude of species now brought together : — 



" Statura et magnitude VespcB vulgaris. Antennas porrectse, 

 fuscse, basi picese. Labium flavum, dentatum. Maxilla; flavse, 

 apice nigraj. Thorax niger, striga antica, lobo postico scutelloque 

 ilavis. In medio dorsi lineolae duse impressae, abbreviatae. Ab- 

 domen glabrum, atrum, primo segmento basi, 2, 3, 4, punctis 

 duobus flavis, reliquis immaculatis. Anus denticulis septem 

 parvis serratus." — Fabr. Syst. Ent. 



