Bucentes. 475 



Skov, Ruderhegn, Ryget Skov, Frerslev Hegn, Tisvilde, Jægerspris; 

 on Rogø south of Sealand; on Møen; on Langeland at Lohals; on 



Fig. 101. Wing of B. geniculata. 



Lolland at Nysted; on Funen at Hoffmansgave ; in Jutland at Sønder- 

 borg, Sottrup, Skeide, Madeskov, Høruphav, Kliplev, Grejsdal, 

 Nebsager near Horsens, Frijsenborg, Holstebro, Dronninglund and 

 Thisted, and finally on Rornholm at Hammeren; the dates are 

 ^/s — ^/lo- It occurs in the same way as maciilata, not rarely near 

 water and often in large number. I have taken it in copula on ^^Z,. 

 The species is known as parasitic on Agrotis plecta and Mamestra 

 brassicae, but seems mainly parasitic on Tipulid larvæ. Two of my 

 specimens are labelled as bred from Mamestra contigua on ^/g (Weis), 

 and one from Tipula paludosa on ^/g (M. Thomsen). 



Geographical distribution: — All Europe; towards the north 

 to northern Scandinavia. Also occurring in North America. 



4. B. flavifrons Stæg. 



1849. Stæg. apud Zett. Dipt. Scand. VHI, 3211, 2 (Siphona). — 1862. 

 Schin. F. A. I, 522. — 1907. Kat. palåarkt. Dipt. III, 381. — B. geniculatus 

 p. p. 1924. Stein, Arch. f. Naturgesch. 90, 6, 127, 2. 



Male. Also this species is similar to the preceding. Head as in 

 cristata; the eyes reaching slightly below the large vibrissa. Orbits 

 yellow, Antennæ large, third joint about four times as long as second, 

 rather broad, reaching below the end of epistoma. Thorax as in geni- 

 culata and with four (generally) postsutural dorsocentrals. Abdomen 

 quite yellow, or as in cristata, yellow with a greyish brown middle 

 line and fifth and most of fourth segment greyish brown; second 

 segment without or with a pair of more or less developed marginal 

 bristles. Legs yellowish with tarsi black. Wings as in the other species. 



Female. Similar; antennæ smaller, but third joint more than 

 twice the second and reaching end of epistoma. Abdomen rather 



