96 MR. F. BALFOUR-BROWNE ON THE LIFE-HISTORY 



EXPLANATION OP THE PLATES. 

 Plate I. 



Figs. 1-5. Colouv-pattenis of Velohius larvfe. Figs. 1 and 2 are taken from lavvie 

 near the end of their first stage, and figs. 3, 4, and 5 from larvae in their 

 third stage. The specimens were merely selecced to show the range of 

 pattern, there being no noticeable difference in different stages of the 

 same larva. 



Fig. 6. Diagram of alimentarj' canal of a Pelohius larva to show proportionate 

 lengths of Stomodieum (S), Proctodaeum (P),. and mid-gut (MG). 



Fig. 7. The egg of PeJobius 24 to 36 hoiirs old. The embryo has begun to appear. 

 Note the large head-lobes, the first signs of the neural canal and the 

 post, end submerged in the yolk, which, at this stage, is not segmented. 



Fig. 8. The embryo about 3 days old (in Ji\ne when incubation lasts only 9 or 10 

 days), showing the appendages appearing, the antennae between the head- 

 lobes and the first abdominal appendages, the last of the series at this 

 particular stage. The yolk is now segmented and the amnion is 

 completely formed. 



Fig. 9. The embryo 4 to 5 days old (in June) ; the amnion still intact. The first 

 abdominal appendages very large and distinct. The depressions at the 

 sides of the thorax and first abdominal segments are, presumabh', the 

 commencements of tracheal-tube formation, though the fact that there 

 is no prothoracic spiracle perhaps makes this doubtful. 



Fig. 10. The embryo 7 or 8 days old (in Jiine). The ej'es have just developed, the 

 membranes have ruptured, rolled back, and disappeared within the dorsal 

 region of the embryo. The first abdominal appendages are now smaller. 



Fig. 11. Front view of head of a third-stage larva to show the relative positions of 

 parts. CL = ('lypeus. LBR=the labral ridge, beneath which are the 

 two epipharyngeal lobes, EP. F is the " fiap " standing up in the 

 "scoop" of the labium, LAB. LAB.P=lal)ial palp. Mx=maxilla, 

 sunk in its base. Mx.P = Maxillar3' palp. M=Mentum. (JU=Gular 

 sclerite of head capsule. ANT = Antenna. 0=Ocelli. MDB = Mandibles 

 which are in a position for seizing the prey. 



Fig. 12. Front view of head as in fig. 11, except that a worm is in the mouth 

 and the mandibles have closed upon it. This diagram shows how the 

 worm is bent upwards hv the mandibles and thus jammed so that it 

 cannot move backwards or forwards. 



Plate II. 



Fig. 1. Mouth-parts of a third-stage larva with labvuni, epipharynx, and "roof" 

 of uiouth removed to show the relative positions of labium (LAB), 

 maxilla (Mx), fully extended, and mandibles (Mdb). S = the " scoop " fully 

 extended and F, the " flap " in the " scoop." Mxl possiblj^ represents the 

 niaxilluhe. Hyp, a dark chitinous plate in the floor of the mouth just 

 where it narrows to the " gullet," presumably represents the hypopharynx. 

 Note the four holes in this plate which seem to be always present. 



Fig. 2. Labium and maxilla as in fig. 1, but with the " scoop " fully retracted and 

 the maxillte almost fuUj^ retracted within their bases. 



F'ig. 3. Ventral view of labium and maxillai, .showing the " scoop " fully extended 

 and one maxilla extended and the other fully retracted within its base. 

 M=mentum, not clearly marked off from the bases of the maxillae, but 

 recognizable. G=the gular sclerite. 



Fig. 4. Ventral view of labium as before, but with the scoop fullj^ retracted. It 

 will be seen therefore that the scoop telescopes into the rest of the labium 

 just as the maxillas do into their bases. 



Figs. 5 & 6. Views of the pro-ventricular spines of a third-stage larva, in situ, 

 showing the backvvardlj' directed " teeth " and hairs on the inner faces. 

 Fig. 5 is a view from above and fig. 6 is a lateral view. These two 

 figures are from camera lucida drawings, and the millimetie scale 

 indicates their magnification. 



