clxxxvi FAUNA HAWAIIENSIS 



open, treeless localities, where are no birds. Many years of collecting had never 

 revealed a large-sized fly maggot in decaying vegetation, not even in the most evil- 

 smelling substances. Besides material of this sort is not found in the dry open country. 

 These flies, so far as is known, are larviparous, the maggot, when born, being already of 

 considerable size, so that there is some approach to the condition of the pupiparous 

 flies. Some years ago Mr Terry reared one of these maggots to maturity on a mixed 

 animal diet, including land molluscs. Later he obtained a new generation of flies from 

 captured specimens kept in large glass jars and supplied with living and dead molluscs. 

 Finally Mr D. B. Kuhns brought back Achatinellas (supposed to have been living 

 when taken, but more probably recently dead) containing maggots, from which the flies 

 were bred. Many shell collectors have noticed the occurrence of maggots in Achati- 

 nelline shells, found still fresh but not living, and we have ourselves sometimes picked 

 up a number so affected in a single day. When one considers the great numbers of 

 mollusca that exist in limited areas in the islands, it is certain that, even in a small 

 area, many individuals must be dying each day of the year, quite sufficient to supply 

 food enough to support the number of existing flies, especially as these when adult 

 are very long-lived. Considering the well-known and very strong odour of dead land 

 molluscs, these would not fail to readily attract creatures so keen-scented as Sarco- 

 phagous flies, probably long before the odour became appreciable to human senses. 

 No doubt many kinds of molluscs serve as food for the maggots, for the flies are 

 common enough in localities where only the thin-shelled Succinea is to be found. 

 Species of this genus are to be found in very dry localities, and would account for the 

 presence of the flies in such places. 



The flies of both Dyscritomyia and Prosthetochaeta are difficult to determine speci- 

 fically owing to the variability of individuals, the variation affecting important structures, 

 e.g. the presence or absence of macrochaetae, which have been considered as of generic 

 importance. Some of the species have very remarkable secondary sexual characters, 

 and the male genitalia will evidently prove of great importance in the determination of 

 the species. These flies are rarely found on the coast in dry districts or on the open 

 forehills, but are common in open places in the forest, and occur also in dense forests, 

 and are frequent above the limit of compact forest. Whether all are feeders on 

 mollusca is of course at present uncertain. It is quite certain that they originally 

 formed the exclusive prey of some of the endemic Crabronidae, and even now some of 

 the latter have never been found to carry off any other kinds of fly. Some species of 

 Nesocrabro may be often seen on the wing hunting beneath masses of fern or 

 Freycinetia in damp shady places for these flies, which presumably are seeking there 

 for fallen molluscs. All the larger species of Hawaiian Crabronids have at times been 

 found carrying them off, and their burrows are frequently packed full of them to the 

 exclusion of all other species. Certainly Dyscritomyia and Pi'osthetochaeta are amongst 

 the most interesting constituents of the Hawaiian insect fauna. 



