238 SUMMARY OF CURRENT RESEARCHES RELATING TO 



unpaired organ below and behind the mouth, which is to be regarded as 

 a hypopharynx ; a third unpaired appendage proceeds from just behind 

 the latter, in the form of a tube ending in two lobes turned back- 

 wards, which is the labium ; the mandibles are elongated and knife- 

 shaped, the maxillae styliform and provided with a pair of palps. In 

 Syrphus the structure of these parts is intermediate between that 

 of these species and that of Musca. The labrum is a veritable 

 proboscis, and has, as in Musca, a basal, median, and terminal division : 

 the basal is thin and shaped like a truncated cone ; the median is thin 

 and cylindrical, chitinized only in the front and hind walls ; the terminal 

 division consists of the lobes which contain pseudotracheae. Within 

 the basal part is a kind of chitinous tube having very much the position 

 of the labium in Hcemafopota and Chrysojjs, being a continuation of part 

 of the oesophageal wall ; it is probably homologous with the labium. 

 The labrum is united with the epipharynx at the base of the labium. 

 The hypopharynx, mandibles, and maxillary palps agree with those of 

 the other two genera, but the maxillee are extremely rudimentary. 

 Empis livida makes a nearer approach to Musca. The labrum is still 

 more closely united with the epipharynx; the maxillte appear to be 

 rudimentary but to have palps ; the mandibles are absent. In Musca 

 the mouth organs consist only of labrum, epipharynx, labium, and 

 maxillary palps. The labrum and labium are developed from paired 

 rudiments, but the former appears to represent the body of a segment, 

 while the latter truly belongs to the series of appendages. Sargus 

 represents a still higher degree of reduction, for the mouth parts con- 

 sist only of labrum, labium, and what are probably maxillary palps. 



Thus the mouth parts of Diptera can be referred to their homo- 

 logues in the typical insect mouth ; they may be either fully developed 

 or much simplified : an epi- and a hypo-pharynx are often present, as 

 processes of the oesophageal wall ; the former usually fuses with the 

 labrum. The modifications in the development of the mouth parts 

 bear a certain relation to the nature of the food and the manner of 

 obtaining it. 



Scent-apparatus of Sphinx lignstri.* — With reference to the 

 experiments of Von Eeichenau f on this subject, K. Fiigner mentions 

 finding that no trace of the characteristic musky odour was emitted 

 by a living male specimen of this insect so long as the animal 

 remained quiet ; but the frequent motion up and down of the folds of 

 skin lying at the base of the abdomen on both sides indicated the 

 position of the organs in question. The scent and tufts of scent 

 hairs become apparent when the wings are gently pressed upwards. 

 When the insect is excited to vibration of the wings by the presence of 

 some vapour of spirit of wine, the skin-folds open out, exhibiting 

 the tufts of hair and assuming the form of raised cups made up of stout 

 brownish scales ; the white scent-hairs form a strong contrast to the 

 darker scales. The hairs perform a peculiar undulating movement, 

 the cause of which was not determined, and the scent becomes at once 



* Entomol. Nachrichten, vi. (1880) pp. 16G-7. 

 t See this Journal, iii. (1880) p. 938. 



