THE FLIES THAT CAUSE MYIASIS IX MAX 117 



The Genus RHLXOESTRUS Brauer 



As in Oestrus, the front is broad and strongly convex, with prom- 

 inent parafrontals which bear, however, instead of pits, numerous 

 tubercles, each provided with a hair : similar although less prominent 

 tubercles may occur on the parafacials. The antennae are short and 

 separated at the base by a distance somewhat less than the diameter 

 of the spherical third segment. The clypeus is depressed above, form- 

 ing two pits which are strongly confluent. The palpi are reduced to 

 the form of two buttons ; the proboscis is greatly reduced, but its cone- 

 shaped rudiment extends backward between the palpi to a level with 

 the posterior margin ( fig. 63) . The legs are short. The wing venation 

 is similar to that of Oestrus : vein t\ is at lea>t halfway along the discal 

 cell; vein m* arises much nearer to the cubitulus than to the cross vein 

 r-m; the petiole of the apical cell curves more or less strongly forward. 

 The abdomen is moderately robust and not strongly flattened: the 

 sternites are narrow, as a rule much under the width of th? exposed 

 membrane on each side, and tend toward a triangular shape ; the hairs 

 of the venter are short and inconspicuous. 



Life Histories. — The larvae are normally parasitic in the head 

 sinuses of various ungulates, including horses, hippopotami, forest 

 duikers, and native Africaai Suidae. One species, Rhinoestrus pur- 

 pu/rus. has been reported to have attacked man in the same manner 

 as does Oestrus oris; however, some records of Rhinoestrus purpureas 

 parasitizing man have been due to misidentifications of Oestrus ovis. 

 As in Oestrus^ first-stage larvae are produced alive and subsequently 

 attack the host through the nasal openings: pupation takes place in 

 the ground. 



Larvae. — The third-stage larvae can be distinguished from those of 

 other genera by the following combination of characters : The 

 antennae are well-separated: each bears a pair of ocelli. Segments 

 3 to 11, are provided with anterior areas of small spines ventrally, 

 each consisting of at least one. usually two or more, complete rows; 

 dorsally. segments 3 to 8 (except in one African species not treated 

 here), are provided with similar spinous areas which may be con- 

 fined to the lateral margins of the segments, but which form at least 

 two complete rows on segments 3 and 4. The posterior spiracles are 

 crescent-shaped and extend around but do not completely encircle the 

 button. The postanal swelling is provided with two conical lateral 

 protuberances. 



The first-stage larvae of Rhinoestrus purpureus may easily be dis- 

 tinguished from those of Oestrus ovis by the characters given in the 

 key. 



RHINOESTRUS PURPUREUS (Brauer) 



The Russian Bot (Russkii Ovodi ; Russian Gadfly ; l'Oestre du Cheval 

 (Fig. 63) 



Synonyms. — Oestrus purpureus (Brauer); Cephalomyia purpurea (Brauer); 



Rhinoestrus nasalis of Brumpt, Fulleborn, etc.. not Oestrus nasalis Linnaeus. 



Recognition Characters. — Adult: The body in general is chocolate brown, 

 the thorax somewhat darker than the head and abdomen and, in life, with a 

 number of purplish spots which often disappear in the dried insect. The abdomen 

 is marked with irregular shining silvery spots which change shape with the 

 light incidence. The antennae are brownish, the third segment being almost or 

 cpnte black. The integument of the head, thorax, and abdomen is adorned with 



