MYDAID^ 605 



the Scenopinidce were allied to the Mydaidce, because in these two families 

 both branches of the cubital fork and the discal vein end before the wing- 

 tip, and he considered that the antennse had some affinity ; in fact he said 

 that the Mydaidce with short antennae appear to be the most undoubted 

 stepping - stone to Scenopinus. In nearly all the characteristics of the 

 Mydaidce one can trace their intermediate position between the Tkomopteka 

 and the Energopoda ; the very long subcostal vein shows close relation- 

 ship to the Asilidm, the tendency to bristles beneath the hind femora 

 and to a small extent on the tibiae affords a connecting link between the 

 spicules of the Tromoptera and the macrochgetse of the Asilidce, the long 

 thin porrect proboscis of Tridonus resembles that of many Bomlylidm, 

 while the shorter stouter proboscis of Mydas leads to the Asilidce, the 

 eremochsetous nature of the head and thorax is shared by some of the 

 Asilidce, even though the latter are considered to be chaetophorous, and 

 the genitalia of the male are more distinct than in the Tromoptera but 

 less conspicuous than in most Asilidce, while the ovipositor in the female 

 of many species has the peculiar circlet of short thick spines which occurs 

 in many Therevidcc and Asilidce. Taken altogether the sequence of 

 families is almost certainly — Bomhylidce, Therevidce, Scenopinidce, Mydaidce, 

 Apioceridce, Asilidce. 



The Mydaidce are said to catch insects with their front legs, but I 

 am unable to trace any positive account of their being predaceous ; Colonel 

 Yerbury's experience of a large Ceylonese species and a small Spanish 

 species has caused his opinion to be that they are not predaceous ; it may 

 be that the formidable appearance of the large species has given them this 

 reputation; Olivier however stated than an Egyptian species was very 

 predaceous on other insects (Uymeno^jtera) which it caught when flying. 

 About a hundred and forty species have been described, which mainly 

 occur in North, Central, and South America, and in Australia, while about 

 a dozen are recorded from the Palsearctic region, and of these only one 

 or two are known with certainty to occur in the extreme south of 

 Europe. Some of the species which occur in Central and South America 

 are the most gigantic forms that occur in the Diptera. One Sisecies 

 is said to be parasitic in the larval stage on Prionida;. 



In the characters given for the Mydaida: the genus Megascelus of 

 Philippi from Chili has been excepted, because it possesses so many 

 characters differing from the rest of the Mydaidce that Gerstaecker refused 

 to admit it into the family, but it cannot be included elsewhere. It 

 has the head much less transverse ; face very short, bare, and retreating ; 

 frons and vertex not at all sunk ; antennae with the two basal joints very 

 short, and the third almost circular and without any style but rather 

 produced to where a style would naturally occur (not very unlike Dolicho- 

 aastcr) ; pleurae witli but little pubescence except for a large rather dense 

 long tuft on the metapleurae ; abdomen without any humps at the basal 

 corners; venation (fig. 333) quite distinct in the position of the discal 

 cross-vein ; both branches of the cubital fork curving up and joining the 



