BOMBYLIIDAE ACROCERIDAE 



489 



spretus are emptied of their contents by the larvae of Systoechus 



oreas and Triodites mus. A similar observation has been made 



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



Callostoma fascipennis, destroys large quantities of the eggs of 



Caloptenus italicus. Still more recently M. Kiinckel d'Herculais 



has discovered that the destructive 



locust Stauronotus maroccanus 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 fly, 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 



/> , i . ~ , , , i FIG. 233. Systropus crudelis. South 



further informs us that in the Mric& . ^ Pupa; B) imag0; ap _ 



Case Of Anthrax fenestralis, which pendages of the left side removed. 

 , ... , (After Westwood.) 



devours the eggs of the large 



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

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

 by 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 Systropus has 

 been recorded as destroying the larva of Limacodes. 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.- Flies of the average size, 

 of peculiar form, the small head consisting almost entirely of the 

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

 entirely concealed by the very large horizontal squamae ; antennae 

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

 that we have already noticed in Bombylius. 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 (Of/codes). There are but 



