BOMBYLIIDAE ACROCERIDAE 



489 



Fig. 233. ~Si/stropus cniddis. South 

 Africa. A, Pupa ; B, imago, ap- 

 pendages of the left side removed. 

 (After Westwood.) 



sjnrfus are emptied of their contents by the larvae of Sijsioeehus 



orcas and Triodiies mus. A similar observation has been made 



in the Troad by Mr. Calvert, who found that the Bombyliid, 



Callostoma fasci2Knnis, destroys large quantities of the eggs of 



Calopteniis itcdicus. Still more recently M. Kiinckel d'Herculais 



has discovered that the destructive 



locust Stauronot'us marocccmus is 



kept in check in Algeria in a 



similar manner, as many as 80 



per cent of the eggs of the locust 



being thus destroyed in certain 



localities. He observes that the 



larva of the ily, after being full 



fed in the autumn, passes the 



winter in a state of lethargy — 



he calls it " hypnody " — in the 



egg-case of the locust, and he 



further informs us that in the 



case oi Anthrax fenectralis, which 



devours the eggs of the large 



Ocnerodcs, the lethargy may be prolonged for a period of three 



years. After the pupa is formed it works a way out of the case 



l>y means of its armature, and then again becomes for some days 



immobile before the perfect fly appears. Lepidopterous larvae 



are also attacked by Bombyliid flies. A species of S^/strojms has 



been recorded as destroying the larva of Zimacodes. Several of 



the Bombyliids of the genus just mentioned are remarkable for 



the great resemblance they display to various Hymenoptera, some 



of them being very slender flies, like the thin bodied fossorial 



Hymenoptera. The difference between the pupa and imago in 



this case is very remarkable (Fig. 233). 



Fam. 21. Acroceridae or Cyrtidae. — Mies of the average size, 

 of peetdiar form, the small head consisting cdmost entirely of the 

 eyes, ctnd bent down under the humped thorax : wings small, halteres 

 entirely concecded ly the very large horizontal squamae; antennae 

 very diverse. The peculiar shape of these flies is an exaggeration of 

 that we have already noticed in Bomhylius. The mouth in Acro- 

 ceridae is very variable ; there may be a very long, slender proboscis 

 (Acrocera), or the mouth-parts may be so atrophied that it is 

 doubtful whether even an orifice exists (Ogcodes'). There are but 



