556 MAJOR K, E. AUSTKN ON THE 



The fact remains, however, that in the adult state dimensions 

 in Pantophthalmido) as a whole are greatly in excess of the normal 

 in Diptera, and this small group of large flies consequently forms 

 an interesting case of the phenomenon known as giantism, con- 

 cerning which Williston \^oj). cit. p. 17) writes as follows; — 

 " Giantism in any group of animal life is a specialization, and is, 

 in general, an indication of approaching decadence ; endui-ingly 

 small races are never the descendants of giants, for decrease in 

 size means lessened vitality and incipient extinction. No strong 

 or dominant group of flies, like the Tachinidfe, Dolichopodidae, 

 Syrphidse, or Bombyliidte, has ever had in the past a larger 

 average bodily size than is found among their living representa- 

 tives. On the other hand, those families composed to-day chiefly 

 of large forms are ones already past their prime. These con- 

 clusions seem established for the larger forms of life, and I believe 

 that they are in the main also applicable to insects." 



(f) Life-history and Bionomics. 



Until the year 1906, knowledge under this heading was limited 

 to a brief, illustrated description by Brauer of a dried larva of 

 Pantophthalmus (Acanthoinera) frauenfeldi Schin. from Bogota 

 {cf. "Bibliography," p. 552); and Osten 'Sacken's statement 

 (Biol. Centr.-Amer., Diptera, vol. i. p. 66), published three years 

 later on the authority of Mr. G. 0. Champion, that " Acantho- 

 mercB are found in forests, alighting on trunks of trees." In the 

 year referred to, however, Karl Eiebrig, of San Bernardino, 

 Paraguay, working under the disadvantages contingent upon 

 isolation and lack of entomological literature, published a most 

 interesting account (cf. " Bibliography," p. 552), illustrated by a 

 series of figures, of the external and internal anatomy of the larva 

 of Pantojihthahmis j^ictus Wied. {infra, p. 575). From the larvie 

 found by him, Fiebrig succeeded in breeding out a pair of 

 imagines, which, owing to the disadvantageous conditions just 

 mentioned, he regarded as belonging to a new species, and 

 accordingly described under the name Acanthomera teretriincum. 



Thanks to Fiebrig's observations, which were actually made in 

 1905, and were confirmed seven years afterwards by Mr. F. W. 

 Urich, in Trinidad, in the case of another species {Pantophtludmus 

 tabaninus Thunb.), we now know that larva? of Pantophthalmidte 

 have the extraordinary habit — unique .among Diptera, so far as 

 the present writer is aware — of boring in the solid wood of living 

 trees, in which they make " nearly horizontal " tunnels, and feed 

 upon the exuding sap. Although Fiebrig does not mention the 

 name of the tree in Avhich he found his larvae, he states that its 

 wood is " among the toughest of Paraguayan timbers, hard as 

 these in general are," and that the tunnels made by the maggots 

 are " sharply gouged out." 



In view of Fiebrig's detailed account, which should be consulted 

 by the student, it is scarcely necessary here to do more than di-aw 



