244 MISS A, L. EMBLETON ON THE ANATOMY 



V. Pupa. (Plate 11. fig. 18.) 



External fonn. — The pupa measures 2-25 mm. in length. The earliest pupal form is 

 not of a uniform black colour, the dorsal surface alone being black. The fully formed 

 pupa is, however, completely black and chitinous, though still enveloped by the cuticular 

 membrane whose origin has been already discussed. The first organs to assume their 

 final colour are the eyes and ocelli, which early become charged with dark red-brown 

 pigment, at a period when the rest of the body is creamy-white ; gradually the colour 

 deepens all over the thorax and abdomen, though the head, apart from the eyes and 

 ocelli, remains almost transparent for a considerable time. When the body has become 

 uniformly black, the ci'eature is in an inert, passive condition, unlike the preceding 

 larval stages, in which slow movements from side to side take place as a result of 

 externa] stimulus. But after a time this black, iuert pupa becomes the perfect insect, 

 and breaks through the enveloping membrane (PI. 11. fig. 18, m.) and the old puj^al 

 cast skin, and with its mandibles cuts a small round hole in the dorsal shell of the 

 Coccid, and escapes, to lead its free existence. 



Tracheal system. — The abdominal plates (fig. 18, pi.) and the radiating tracheae are still 

 present, but when the imago emerges they are left behind with the old sheathing 

 membrane. The pair of trachese which radiate out from tlie head region never develoj) 

 these oval red plates at their bases ; it may be that these plates are more connected with 

 excretion than respiration. The nymphal respiratory arrangements are apparently 

 very transitory. 



In order to obtain, if possible, more detailed and exact knowledge of the larva and 

 pupa while still witliin the host, I cut the undissected host into a series of sections with 

 the microtome. To do this I tried various methods for softening and cleaning the 

 chitin, but the most successful results were obtained when I employed eau de Javelle 

 or eau de Labarraque, as suggested by Looss. The chitin in this way was rendered 

 transparent and permeal)le to reagents. I first hardened the specimens, and then 

 left them in 25 per cent, eau de Javelle for 18 to 24 hours, afterwards washing out 

 thoroughly with water. They were then dehydrated, embedded in paraffin, and good 

 sections were obtained ; sometimes I stained, before embedding, with alum-carmine or 

 picro-carmine (five to six days), but usually I found it best to stain the sections when on 

 the slide. 



But though the sections were good, there was little or nothing to be'made out by this 

 method of investigation, which Mas not seen better in macroscopic dissections ; except, 

 of course, histology, but that I have been content to omit. 



IV. Anatomy of Imago, ? . 



(a) Measurements. — Length (without antennae) 2-5 mm. ; length of thorax -9 mm. ; 

 width of head -75 mm. ; width of thorax -74 ram. ; width of abdomen 74 mm. ; length 

 of abdomen -85 mm. ; length of antennae 1-25 mm. ; extent of fore wing 1-5 mm. ; 

 extent of hind wing 1-25 mm. ; width of fore wing 02 mm. 



(b) Antenna (PI. 11. figs. 19, 20; PI. 12. fig. 21).— The antennae are relatively long 



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