OF THK MALTESE ISLANDS. 61 



Thorax (fig. 8, p. 63). This consists laroely of the meso-thoracic division, 

 the prothorax being represented by a very short extension which can be seen 

 more or less distinctly in examples which have been macerated and mounted in 

 Canada balsam. The scutellum and post-scutelliim are well developed and 

 conspicuous in mounted preparations. 



Abdomen. — ^This is composed of ten segments, the last being modified by the 

 external genitalia. In the female the appendages are simple, flattened, leaf -like 

 structures, densely clothed with hairs and arranged in two pairs (figs. 8 and 10). 

 In the Maltese species they are all so similar in structure as to afford no 

 diagnostic characters of importance. Annandale (1) states (p. 41) that these 

 organs " become distorted and shrivelled in dried specimens." These structures 

 can, however, be restored by maceration in caustic potash but the best results 

 may be obtained by preserving the specimens in alcohol. 



External genitalia of the males. — These are large and complex structures 

 (figs. 14-18, pp. 70-74) and aflPord a ready means of determining the sexes ; 

 moreover, their morphological characters are of great importance as they present 

 very marked specific differences whereby the closely allied species may be readily 

 distinguished. These appendages are arranged in five pairs as follows : — 

 Superior claspers (sc in all the figures). These are placed dorsally and are 

 larger than any of the other structures ; they are composed of two distinct 

 segments, of which the terminal or distal one is the smaller and is provided at 

 the apex with large spines, which in some species are curiously modified. They 

 are generally densely hair}' and large scales may also be present ; but both hairs 

 and scales are easily deciduous and the greater portion of them usually fall 

 away during the process of mounting for microscopical study. The accom- 

 panying illustrations must therefore be considered as representing these structures 

 in a partly denuded condition. Inferior claspers (ic). These are nnisegmented 

 and much shorter than the superior pair ; they are venti-ally placed and may or 

 may not have modified spines at the distal extremity. Suhmedian lamellae. 

 These lie between the inferior claspers, and although they are usually short, 

 thin, leaf-like structures, in some instances {P. minutus) they are very similar to 

 the clasper both in form and length. Intermediate appendages (ia). These occupy 

 a Tuedian position and are often curiously modified ; they form a branch of the 

 superior clasper and are sometimes bi-lobed. Intromittent organ (io). This is 

 homologous with the"juxta" in Glossina, and is described as the penis by 

 Grassi. It consists of a pair of long slender and highly chitinised organs which 

 lie between the intermediate appendages. These completely ensheath the two 

 long filamentous processes which form a continuation of the ejaculatory duct 

 leading from the penultimate segment of the abdomen. In P. piapatasii they 

 have not been seen to extend beyond the intromittent organ or penis, while in 

 P. perniciosHs (figs. 16, 17, p. 72), though lying apparently in a normal resting 

 position, they project beyond it to a distance equalling one-half the length of the 

 sheath. 



Wingf. — This is densely hairy, and may at once be distinguished from that of 

 the mosquitos (Culicidae) by the entire absence of scales, the double fork 

 of the second longitudinal vein, and the proximal position of the cross-veins. 



