34 ANNALS OF SCOTTISH NATURAL HISTORY 



Muscids in autumn, Bibionids in autumn, Scatophagids in autumn, 

 and in autumn also the orders of small flies such as Cecidomyidse, 

 Ephydridas, Chloropidse. 



We have observed of the Bombi that their autumnal and vernal 

 maxima were determined by the great abundance of one or two 

 species ; the same is true of the short-tongued Diptera. The 

 autumnal maximum of Bibionidse is almost entirely due to Bibio 

 pomontz, K, of Muscidae to Pollenia rudis, F., and of Tachinidae to 

 Siphona geniculata, Deg., which increases in number from May 

 onwards ; while the vernal abundance of Anthomyida; is due to one 

 or two species of Anthomyia and Trichophthicus. 



Long-tongued Flies. The long-tongued Diptera, like the short- 

 tongued, increase numerically from si' miner to autumn, but in our 

 observations they did not show a vernal maximum. Their numbers 

 in autumn were very largely due to two insects Eristalis pertinax, 

 Scop., and Empis tessellata, L. the first a Syrphid, the second an 

 Empid. When we study the seasonal distribution of the Syrphidaa 

 we see that the larger bodied have an autumnal maximum, but not 

 so the smaller species, the commonest genus of which is represented 

 throughout the three seasons by a succession of representatives, 

 thus : Platychirus discimanus, Loew (spring), P. inanicatus, Mg. 

 (summer), and P. albimanus, F. (autumn). 



TABLE VIII. SEASONAL DISTRIBUTION OF LONG-TONGUED FLIES. 



Spring. Summer. Autumn. 



Larger Syrphids 1 .... 24 120 473 



Small Syrphids " . . . 236 218 234 



Larger Empids. . . . .159 169 559 



The greatest variety of Syrphids is to be seen in summer, and 

 indeed the greatest variety of every group of anthophilous insects, 

 whether with a vernal or an restival or an autumnal maximum. Of 

 Syrphids summer has 34, autumn 12, and spring 10; of Empids 

 summer has 22, autumn 10, and spring 9. Rhingia campestris, 

 Mg., is among the summer Syrphids; it seems to have a very 

 short period of flight just at mid-summer. Volucella is a summer 

 insect ; the commonest Chilosia-C. fraterna, Mg., is also a summer 

 insect ; Sericomyia boreahs, Fin., is an autumn insect. Empis 

 tessellata, F., which is autumnal chiefly, is the largest and longest- 

 tongued of the Empidae at Clova, and it associates with Pachymeria 

 palparis, Egg., an insect not much smaller. The smaller Empids, 

 like the smaller Syrphids, are not autumnal. 



Autumn Jiiis the longest-tongued of the short-tongued Flies. It has 



1 Genera here included are : Rhingia, / 'olucella, Sericomyia, Eristalis, 

 Ifclophihts, Chilosia, Lcucozonia and Chrysogaster. 



2 Genera here included are : Syrp/nis, Syrit/a, riatychirus, Melanostoma 

 with Melangyna)) Ascici and Sphtzrophoria, 



