120 Orthorrhapha brachycera. 



base of the costa there is a small, triangular prominence (answering to 

 the præalar hook). Alula large, hairy at the margin towards the base ; 

 alar sqiiamula fringed at the margin ; frenulum with long hairs. 



The larva and pupa of B. minor (determined as pumilus Meig.) 

 have been thoroughly described and figured by Nielsen (Zool. Jahrb. 

 18, 1906, 647, Taf. 28), and I am indebted to Mr. Nielsen for examin- 

 ing his material. The larva was found in the cells of Colletes 

 daviesana. The fuU grown larva is white, cylindrical or somewhat 

 flattened, consisting of thirteen segments. The head is small and 

 retractile; the mouth parts consist of a median, somewhat hook- 

 formed labrum, knife-shaped, somewhat serrated mandibles, and large, 

 lobe-shaped maxillæ with a one-jointed palpus; at each side of the 

 labrum above there is a small, one-jointed antenna. The larva is 

 amphipneustic with a pair of spiracles on prothorax and another pair 

 on the penultimate segment. According to Nielsens investigations the 

 larva moults three times during growth and alters its shape on each 

 moulting. The young larva is slender, the three thoracic segments 

 have each a pair of long bristles; there is a pair of tubercles (Fuss- 

 stummel) at the anterior margin of the second to sixth abdominal 

 segments on the ventral side, the penultimate segment has a pair of 

 larger tubercles, and at the apex of the body there are two long 

 bristles. The larva is in this stage metapneustic, having only the 

 posterior spiracles. In this stage the larva eats the pollen stored in 

 the bee-cell. When the larva has reached a length of 2 mm., it attacks 

 the Colletes larva; having fixed itself on the host it moults, and its 

 shape changes; it is now relatively thick, without bristles or tubercles, 

 and it has acquired the anterior spiracles. When the larva has reached 

 a length of 8—9 mm. it moults again and passes to the third stage; 

 it is now broader, the segments have somewhat dilated margins, and 

 the body is not quite cylindrical but somewhat flattened. The mouth 

 parts also are a little altered during the growth. When the larva is 

 full grown it has a length of 10 — 12 mm., it now rests about fourteen 

 days and then pupates. — The pupa resembles the Anthracid pupæ; 

 it has on the front of the head at the base of the antennal sheaths 

 two strong, downwards curved spines which are triangular in section, 

 at the end of each antennal sheath there is a pair of similar spines, 

 and on the ventral side at the base of the proboscis another pair, 

 thus in all eight spines; behind the pair at the end of the antennal 

 sheath there is a curious, movable, palp-like organ with a pencil of 

 hairs at the apex, There are some long hairs on the head. On the 

 dorsal side of the second to sixth abdominal segments there is a 

 transverse row of somewhat semiannular, chitinous hooklets, arranged 



