191 Ij Muir and Kershaw — Embryology of Head of Pristhesancus 75 



ON THE LATER EMBRYOLOGICAL STAGES OF THE 



HEAD OF PRISTHESANCUS PAPUENSIS. 



{REDUVIIDAE) 



By F. Muir and J. C. Kershaw. 



Mossman, North Queensland. 



The authors, in a former paper,* based on anatomical studies 

 of the adult heads of Hemiptera, drew certain conclusions as 

 to the homologies of their mouth-parts. Wishing to see if these 

 conclusions could be verified by embryology, the studies herein 

 described were undertaken on the embryo of Pristhesancus 

 papuensis. 



For our present purpose it is only necessary to begin our descrip- 

 tions from the fifth day after the eggs were laid. 



oth day. (Fig. 1) At this stage the embryo is in a dorso- 

 ventral position. The procephalic lobes are large, and the anten- 

 nae distinct. All the appendages are distinct, but the 1st maxillae 

 are plain, single lobes, as are also the 2nd maxillae. There is 

 no sign of the eyes. Two small lobes over the stomodaeum repre- 

 sent the labrum. 



6th day. (Fig. 2) There is a deep constriction between the 

 procephalic lobe and base of antenna. The appendages are 

 longer and the legs have two distinct joints. The embryo has 

 a posterio- ventral position. 



7th day. (Fig. 3) The first maxillae are now two-jointed, 

 the basal joint we will distingusih as the maxillary plate, the 

 distal as the maxillary seta. The 2nd maxillae are distinctly 

 three-jointed. Legs also three-jointed. Eyes not yet apparent. 

 Labrum more pronounced with the two lobes amalgamated. 



8th day. (Fig. 4) The antennae have partly unrolled, and 

 all the appendages lengthened. 



Oth day. (Fig. 5) The maxillary plate and maxillary seta 

 are separate up to their bases. The labrum has come forward 

 and developed. The 2nd maxillae have coalesced except at their 



*0n the Homologies and Mechanism of the Mouth-parts of Hemiptera. Psyche, vol. 18, Feb. 

 1911. 



