36 



MARDWJCKE'S SCIENCE-GOSSJF. 



opposed to any method that wets them, as it mats the 

 pubescence and frequently prevents indentification. 



For mounting, I recommend the long Carlsbad 

 pins, of which Nos. o to 4 are the most useful ; the 

 very minute species being pinned with the " minutien 

 Nadeln," German pins, which are then stuck at one 

 end of a small oblong piece of white pith, a Carlsbad 

 No. 4 pin being put through the other end, and the 

 pith pushed half way up the long pin. (See 

 diagrams.) 



The larger specimens should be placed above the 

 middle of the pin, which should pierce the centre of 

 the thorax. 



I adopt the long pins for the following reasons : 



I. The specimens are exchangeable with conti- 





Fig. 13.— Methods of mounting Diptera. 



nental correspondents, all of whom adopt this method 

 of pinning. 



2. They are easier to handle and therefore less 

 liable to accident. 



3. They allow a higher magnifying power to be 

 brought to bear on them when in the cabinet by 

 being nearer the glass. 



A second important point to be observed in 

 mounting is not to set the flies. They are as useful 

 for scientific purposes unset as set, they are easier to 

 handle, less liable to accidents, exchangeable abroad, 

 and by not setting them a vast amount of time is 

 saved. 



I am aware that, on this point my opinion is 

 directly opposite to that of our leading dipterologist, 

 but still see no reason to change it, as it is only in 

 exceptional instances that unset specimens cannot be 

 identified, provided the directions given below are 

 followed. 



So long as the wings are extended vertically (and 

 not allowed to cling together) and the. legs kept from 

 folding up close under the thorax, there is no difficulty 

 in naming them, which is the chief objection raised 

 by those who insist on the necessity of setting. 



Their second plea — lack of uniformity in unset 

 specimens — appears unsupportable, as a collection of 

 Diptera pinned in the continental style seems to me 

 as' uniform and elegant as one in which the legs 

 and wings are extended after the fashion of setting 

 Lepidoptera. Moreover much cabinet space is saved 

 by not setting them. 



Every specimen should be dated and localised 

 with a ticket attached to the pin below the insect. 



Specimens may be relaxed by placing them in 



laurel, and for preservation against mites when in 

 the cabinet, naphthaline is' most frequently used by 

 continental authorities, it being almost unnecessary to 

 add that the cabinet should be kept in a warm dry 

 room. 



4. CLASSIFICATION. 



Hardly any author's classification can be con- 

 sidered a standard one, the order having undergone 

 such important revision during the last twenty years. 



Several of the older authors, owing to their in- 

 complete knowledge of the order, added altogether 

 to our lists some hundreds of species that have no 

 right to a place there. 



Moses Harris was the first to write on the British 

 diptera, and relied chiefly on the neuration as a basis 

 of classification. 



Curtis' work (1823-40) gives 112 really excellent 

 coloured plates, and notices many species that he 

 does not illustrate ; his generic descriptions also 

 being complete, and, in the main, trustworthy ; but 

 no attempt is made at analytical tables of genera or 

 species, and many of the introduced species are now 

 repudiated. 



In Walker's work (1851-56), about 2CXX) species 

 are described, though scores (I might almost say 

 hundreds) of these descriptions are worthless. His 

 work, however, is a most useful one to have, as a 

 good general knowledge of the order can undoubtedly 

 be obtained from it. 



His analytical tables are not always g«od. He 

 divides the order into three great groups, as fol- 

 lows : — 



Antennae lying flat in cavities in the head : Suctoridea 



{PulicidcE). 

 Antennae seated on the front of the head. 



Legs at juncture with thorax close together : Pra- 



boscidea. 

 Legs at juncture with thorax wide apart : Eproboscidea. 



His table of families is unsatisfactory, inasmuch as 

 two families (Empidtt and Muscidce) are split up and 

 fall in both his subdivisions q{ Brachycera. 



He divides the Proboscidea as follows : — 



Antennae with distinct joints, at least six, usually more 



than 10 : Neinocera. 

 Antennae, three to ten jointed, after the third closely 

 jointed. 



Posterior veins branched or interlacing : Brachycera. 

 Posterior veins simple, detached, faint : Hyfocera 

 [Phorida:). 



He gives nine families of Nemocera, seventeen of 

 Brachycera y and two oi Eproboscidea. 



Books on this order are few and costly, the follow- 

 ing being the principal ones relating to British 

 Diptera :— Moses Harris, "Exposition of British 

 Insects," 1776-1782. Curtis, " British Entomology,"' 

 1823-1840. F. Walker, " Insecta Britannica : Dip- 

 tera," 1S51-1856. Rev. F. O. Morris, "Catalogue 

 of British Diptera," 1865. G. H. Verrall, "List of 

 British Diptera," 1SS8. 



No student should be without Mr. Verrall's list. 



