NOTES ON THE MYIASIS-PRODUCING DIPTERA. 255 



this SO, when the}^ have to determine a larva taken from a sheep in this country. 

 A careful examination of the plates when cleared in caustic potash and mounted on 

 a slide will, however, help to separate the species. In the larva of Calli-phora crythro- 

 cephala, as well as in that of C. vomitoria, the plates are distinctly larger and further 

 apart than those of the larva of Lncilia scricata. In addition, in CallipJwra there are 

 two processes of the rim which project in between the upper and middle slit, and the 

 middle and lower slit, whereas in Lncilia sericata there is only one projection between 

 the middle and lower slit. These points, together with certain differences between 

 the cephalopharyngeal skeletons and anterior spiracles of the two species, will make 

 identification easy, but it is necessary to point out that mere examination of the 

 larvae with a hand lens is not sufficient. Plate vi, fig. 13, illustrates the posterior 

 stigmata of the third-stage larva of Anaslcllonhina augur, and it will be noted that 

 they are very similar to those of Calliphora. This alone, in my opinion, indicates 

 the affinity of this blow-fly. The larva of Cynomyia cadaverina also has posterior 

 stigmata of this type, as is seen in fig. 9 ; here, however, the clear spaces are not seen. 

 The posterior stigmata of Lucilia argyyicepluda are smaller than those of L. sericata 

 and more widely separated. 



In the larvae of Chrysomyia and Cochhomyia the posterior stigmata appear to 

 have a break in the chitinous ring on the lower and inner face, the plates are, as a 

 whole, larger, and the button area is situated at the lower angle. Plate vi, figs. 14, 

 15, 16 and 17, illustrate the posterior stigmata of the larvae of Chrysomyia mega- 

 cephala, Chrysomyia bezziana, Cochliomyia macellaria and Phormia regina, which also 

 belongs to this group. It is interesting to note that in the case of the two myiasis- 

 producing species, macellaria and bezziana, the slits are short and wide, those of 

 bezziana having characteristic clear spaces between and near the slits ; these two 

 flies are evidently very closely related. 



Apart from other differences, such as the shape of the truncated posterior end, 

 the larvae of the Sarcophagi! )AE can always be distinguished from those of any of 

 the Calliphorinae by noting that the posterior stigmata are situated in a deep cleft, 

 and that the internal slit slopes downwards and outwards, the middle almost 

 straight down, and the outer sht a little inwards and backwards. The 

 plates are always large and the slits long and somewhat narrow, and there is a 

 characteristic break in the chitinous ring at the inner and lower angle ; the posterior 

 stigmata of the third stage larvae of a species of Sarcophaga taken from a case of 

 cutaneous nu'iasis in India are shown in Plate vi, fig. 18. The cephalopharynx and 

 anterior spiracles of the larva of Sarcophaga are also very distinct, as I will pr)int out 

 further on, so that there should never be any difficulty in identifying a larva of this 

 family of flesh-flies. 



The posterior stigmata of the larvae of the elephant bots are very characteristic. 

 The plates have here coalesced and the chitinous ring is feebly developed, the margins 

 of the ring being probably represented by an island of chitin on the inner face. 

 The sHts are long and almost straight, situated close to one another ; fig. 6, Plate v, 

 illustrates the posterior spiracles of the third-stage larva of Cobboldia elephantis from 

 the Indian elephant. The button area has apparently disappeared in this type of 

 posterior stigmata. On larval structure alone, then, Cobboldia suggests affinities with 

 a Calliphorine on the one hand and a Sarcophaga on the other. 



3. Single round or oval openings. This type of posterior stigmata is well seen in 

 the third-stage larva of the sheep nose-bot. Oestrus ovis. The plates are large, some- 

 what kidney-shaped, and the whole surface is dotted with minute openings of varying 

 shapes and sizes. The button area is well marked and almost central in position. 

 A similar plate is seen on the larva of the camel hot, Cephalopsis titillator, Plate v, 

 fig. 7 ; the button area here is situated about the middle of the inner face of the plate, 

 and is somewhat difficult to see. The posterior stigmata of the larva of Hypoderma 

 (Plate V, fig. 8) also belong to this type, the openings here being arranged in more 

 (4183) T 2 



