GARDEN PESTS IN NEW ZEALAND 



When the head of a weta, grasshopper, or cockroach is removed 

 from the body and boiled for a few minutes in a 10 per cent, solution 

 of caustic potash, and then washed in water in order to remove the 

 muscles and other tissues, a large opening will be seen on the posterior 

 surface where the head was attached to the thorax; also, if the mouth 

 appendages are pulled apart, they will be seen to surround another 

 opening on the lower aspect of the head capsule, marking the position 

 of the mouth. The digestive canal passes from the mouth through the 

 posterior opening into the thorax. 



The mouth appendages are as follows (Fig. 3) : Suspended from 

 the fore aspect of the mouth opening is a more or less conspicuous 

 movable flap, which forms the upper lip, while from the posterior 

 aspect of the same opening is another suspended appendage forming 

 the lower lip; this latter appendage is really] a complicated one, and 

 bears a pair of short, jointed appendages the palps which are sensory 

 organs, while on its inner surface i.o., within the mouth is a swollen 

 area or tongue, an organ very greatly "modified in certain insects. 

 Between the upper and lower lips, and suspended from both sides of 

 the mouth opening, is a pair of true jaws immediately behind the upper 

 lip, followed by a pair of accessory jaws immediately before the lower 

 lip; these jaws do not move up and down, but have a side-wise action, 

 closing and opening like scissor blades. While the true jaws are each 

 of one piece, the accessory jaws consist of several parts, and each bears 

 in addition a jointed palp, as in the case of the lower lip. The upper 

 and lower lips serve to hold the food in the mouth, the true jaws 

 nibble or tear oh* portions of the food and masticate it -(if -the term 

 can be used), while the accessory jaws, aided by the lower lip 1 , manipu- 

 late the food during the process of feeding. 



The comparatively simple arrangement of mouth parts found in 

 the weta, grasshopper, and cockroach, as described above, is characteristic 

 of all insects that gnaw or chew their food e.g., earwigs, beetles and 

 their larvae or grubs, the caterpillars of moths, and! so on. There is, 

 however, a vast number of insects that has developed more or less 

 complex variations of this generalised pattern, according to the manner 

 of feeding. 



Hie mouth parts of the worker honey-bee, for example, have the 

 jaws adapted for eating pollen and moulding wax for the comb ; the 

 accessory jaws, however, are lengthened, though their palps are reduced 

 to mere vestiges in contrast with the elongated palps of the lower lip ; 

 the most remarkable modification is that of the greatly elongated 

 tongue, with its spoon-like tip adapted for reaching nectar of flowers 

 having deep-seated nectaries. For the same purpose, the mouth parts 

 are modified in a moth (Fig. 3) to form a long proboscis, which lies 

 curled up in a spiral beneath the head when not in use; in this case 

 the proboscis is the modified accessory jaws, the remaining mouth parts, 

 with the exception of the well-developed palps of the lower lip, being 

 greatly reduced. In a blood-sucking insect, such as* the female mosquito, 

 all the mouth parts are well developed, but are very delicate and greatly 

 lengthened and suited for piercing the skin. The greatest modification 

 is found in the blow-fly proboscis, which is a soft, sucking tube, with no 

 outward resemblance to the generalised plan, except for the palps of 

 the accessory jaws. The mouth parts of insects (e.g., aphids) which 



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