30 INTRODUCTION. 



5. THE MOUNTING AND PRESERVATION or DIPTERA. 



Regarding the mounting of specimens for the cabinet, a great 

 deal has been written, and it is not proposed to dilate on the 

 subject here. 



Some specialists prefer specimens in alcohol, asserting that the 

 more delicate parts of the body, such as the structure of the 

 mouth and antenna?, and the genital organs of the male, are more 

 easily viewed thus, through remaining soft, whereas in dry speci- 

 mens they are liable to shrinkage, and possibly a certain amount 

 of distortion, their relative proportions thereupon being lost. 

 Those who prefer specimens in spirit are generally workers in 

 those groups that I have never studied myself, CECIDOMYID^E, 

 CHIRONOMID^E, etc., and therefore it might be presumption to 

 appear to dictate as regards these families ; but individually I 

 have a very great distaste for any Diptera so preserved. 



The relative proportions can be noted during life, as Osten 

 Sacken did in many instances of Tipnlid genitalia, antennae and 

 so on ; and dried specimens are infinitely easier to handle, they 

 preserve their colours in the vast majority of families for as long 

 as probably nearly a hundred years, if kept in suitable cabinets, 

 properly supervised, in a temperate climate, and lastly their external 

 vestitnre is retained in its natural state. Pubescent species, 

 , such as BOMBYLIID^E, ASILID^:, THEREVID^:, etc., are most certainlv 

 utterly ruined, if placed in alcohol (Williston says all specimens 

 so preserved are worthless) ; the insect when lifted from the 

 liquid bearing no possible resemblance, in its bedraggled condition, 

 to its natural appearance. 



It should be hardly necessary to state that Diptera gummed on 

 slips of card are not to be tolerated either, as the underside is 

 thus rendered practically invisible. 



Therefore I, personally, pin everything, using Carlsbad white 

 (not steel) pins : nos. 4 and 5 for the very largest ASILIDJB, 

 TABANID.E and so on ; no. 3 for ordinarily large flies, and nos. 

 2, 1 and for the great bulk of the species. Nos. 00 and 000 are 

 too fine to use by themselves, and I prefer at that stage to resort 

 to the short very fine pins used for very small Lepidoptera, made 

 by Kirby and Spence, also the "minutien nadeln" (without heads) 

 manufactured by some German firms. These I should employ 

 for species of the size of Simulium, for the bulk of the' 

 MYCETOPHILID^;, the CHIRONOMIDJE, Cui/iciDjE and others of 

 similar size. 



When mounting specimens on full-length pins, the latter should 

 pass through the middle of the dorsum of the thorax, and the 

 insect be placed sufficiently high up the pin to leave only 

 sufficient room above it to grasp the pin easily with the forceps ; 

 and in a properly mounted collection the dorsum of all the 

 specimens would be at the same cabinet level (fig. 6, ). This very 

 greatly facilitates examination with the lens, often rendering it 

 unnecessary to remove the lid of the cabinet drawer. 



