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XII. A Contribution towards the knowledge of the Anthomyid 

 genera Hammomyia and Hylephila of Rondani 

 (Diptera). By J. E, Collin. 



[Read June 2nd, 1920.] 



Plates VII— X. 



In the Hylemgia-Chortophila section of the Anthomyidae, 

 which includes the only too well-known " Onion-fly " and 

 " Cabbage-Root-fly," the larvae are principally vegetable 

 feeders; but there exists in that section a small group of 

 species the life-history of which is intimately connected 

 with that of various Hymenoptera — usually of the family 

 Andrenidae. The female flies haunt the neighbourhood 

 of the burrows which the bees make use of for breeding 

 purposes, and, so far as is known, the larvae of the flies 

 live upon the pollen-masses stored by the bees. 



This group of flies are principally distinguished by their 

 having a very " buccate " head with broad facial orbits 

 (genae) and jowls (buccae), and the eyes of the females 

 seldom very widely separated on the frons — often almost 

 as approximated as in the males. A more complete 

 diagnosis would be as follows : — 



Eyes bare, often only very narrowly separated on the frons in 

 both sexes, never very widely separated in the male, and when the 

 frons is wide in the female, the frontalia are narrow (not wider 

 than the frontal orbits) and without strong crossed bristles. Facial 

 orbits and jowls wide, often very wide, giving the head a " buccate " 

 appearance. Arista almost bare, distinctly pubescent, or rarely 

 (grisea) plumose. Thorax without conspicuous dull black mark- 

 ings, and scutellum without dark patches at the sides. Two pairs 

 of presutural doi-socentral bristles. Strong sternoplem-al bristles 

 ai-ranged 1 : 2 (male), or 1 : 1 (female), — never 2 : 2. Abdomen with 

 more or less conspicuous tessellated markings and central brown 

 stripe. Hind-marginal bristles strong and conspicuous. Male 

 hypopygium not swollen or projecting dorsally above the level of 

 abdomen. Penis often much flattened, and always with a chitinous 

 strip each side ending in a pointed process. Projections of the 

 last male sternite not very conspicuous and never shining black 

 TRANS, ENT. SOC. LOND. 1920. — PARTS III, IV, V.(aPR.' 21 ) X, 



