376 NATURAL ARRANGEMENT OF INSECTS. 



antennae, they are connected with Ceria among the 

 Syrphidce, and their tongue associates them with the 

 Muscidce. They have a very elongate,, slender, and 

 geniculated proboscis ; and in the perfect state frequent 

 flowers ; but in the larva state they live as parasites 

 within the bodies of the Bombi. The next tribe, the 

 Myopidce, greatly resembles them, although sufficiently 

 distinct ; and their early stages are not known. 



(337.) We now enter the remarkable tribe of the 

 (Estridce, which are all parasites upon some part of the 

 body of the Mammalia; and it is a singular anomaly, 

 that some of the genera which contain the largest spe- 

 cies among them, inhabit the smallest animals. Thus, 

 Cuterebra, an American genus, and a giant in the 

 group, inhabits the backs of rabbits, rats, and mice; 

 whilst (Estrus inhabits the stomachs of horses/ CEde- 

 magena, the facial cavities of the reindeer ; and Hypo- 

 derma forms tumours upon the backs of oxen. In 

 their structure, they are also remarkable ; as among them 

 we find the only Diptera that want a mouth, which is 

 wholly deficient in Cephalemya, which inhabits sheep, 

 Colax, and (Estrus; and in Cuterebra and Hypoderma, 

 although there is a buccal cavity, there is no proboscis 

 or palpi. Although thus imperfectly organised, their 

 general analogy, in many other points, to the higher di- 

 visions of the Muscidce, assign to them this situation. 

 The remarkable dread with which cattle view their ap- 

 proach has given a name to the tribe, and animals resort 

 to every manoeuvre to prevent the insect depositing its 

 egg upon them; but vainly; for neither swiftness nor 

 immersion in water will evade their antagonist. They 

 are supposed to act as counter-irritants upon the system 

 of these large animals, and thus to modify the effects of 

 grass feeding and repletion. They certainly form a 

 highly interesting tribe, and one that has occupied the 

 laborious and thorough investigation of Bracy Clarke, 

 the celebrated veterinary surgeon, whose skill and pa- 

 tience have elucidated the obscurities of their history. 



(338.) We now enter the enormous tribe of the 



