99 
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MONOGRAPH OF THE GENUS MASTAX, BELONGING TO THE FAMILY OF 
THE TRUE LOCUSTS. 
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Tue insects of the genus Mastax, of Perty, illustrate a peculiarity 
in Entomo-geography, which does not appear to me to have been 
sufficiently noticed, namely, the occurrence of species belonging to 
aberrant and anomalous genera, in very distant localities, often 
indeed in different quarters, of the globe. The Mole-crickets offer 
a striking instance of this peculiarity. The genus is very anoma- 
lous in many of its characters, yet we find species mn each of 
the five continents (including New Holland). The two species of 
Mastax hitherto described (from unique individuals), are natives of 
the New World, whilst the three additional ones represented in 
the accompanying plate, are natives of the Islands of the Indian 
Archipelago. 
The genus (in addition to the great rarity of the species) is 
especially interesting on account of various structural peculiarities. 
The fore wings are in some species quite hyaline and almost colour- 
less, which gives the insects an appearance quite unlike the rest of 
the family. The head is very much elevated above the level of the 
prothorax. The antennze are composed of very few joints; the 
three ocelli are placed between the eyes ; the palpi are very short ; 
the three sternums are simple, the hind-legs long, the tarsi 3- 
jointed, with a moderate sized pulvillus between the ungues. The 
anal appendages in M. mutilata are described by Serville as 
‘courts et droits,” but in the males of M. apicalis and M. guttata 
they are dilated and contorted in a singular manner quite unlike 
any of the rest of the family. 
As to the natural relations of the genus, Burmeister (who how- 
ever had not seen it in nature) places it between Gomphocerus and 
Ommexecha, whilst Serville (who had two species before him) 
introduces it (with several other curious genera) between Gom- 
phocerus and Tetrix. It appears to me, however, much more 
closely allied to Proseopia of Klug, with which it agrees in the 
elevated head and short few-jointed antenne. 
H 2 
