. A text-book of invertebrate morphology. Invertebrates. 520 IN VERTEBRA TE M0RPH0L06 T. metathoracic pair being usually represented by a pair of club- shaped bodies on the sides of the segment, termed halteres or balancers. The wings are always trans- parent and the veins by no means abundant. In a few forms, such as the Sheep-tick {Melophagus) and the Fleas (Pulex), the wings are entirely wanting in harmony with the parasitic habits which these forms possess, but they form exceptions to the general rule. The mouth-parts are adapted for sucking and also for piercing; the labrum (Fig. 245, Ir)
. A text-book of invertebrate morphology. Invertebrates. 520 IN VERTEBRA TE M0RPH0L06 T. metathoracic pair being usually represented by a pair of club- shaped bodies on the sides of the segment, termed halteres or balancers. The wings are always trans- parent and the veins by no means abundant. In a few forms, such as the Sheep-tick {Melophagus) and the Fleas (Pulex), the wings are entirely wanting in harmony with the parasitic habits which these forms possess, but they form exceptions to the general rule. The mouth-parts are adapted for sucking and also for piercing; the labrum (Fig. 245, Ir) and labium (la) are prolonged into grooved processes, forming together a tube within which lie, in the female -Mosquitoes {CuLex) and Gadflies {Tahanus), two pairs of elongated needlelike rods which repre- sent the mandibles (md) and maxillae (mx), to which a fifth unpaired stylet may be added which arises as a growth from the lower wall of the pharynx Qiy). In other forms the maxillae only OP A Gnat, Oulex, the have the acicular form, the mandibles Labbum turned to fusing with the labrum, and in all cases the maxillary palps are present, while the labial palps are undeveloped. In the ordinary House-fly (llitsca) the ex- tremity of the sucking-tube is expanded into a disklike structure, and in all forms the salivary glands open near the extremity of the tube, usually maggotlike (Fig. 244), entirely destitute of feet, and in some forms the head even is indis- tinguishable. The metamorphosis is complete, the pupa being in the Mosquitoes active, swimming about in water, though more usually it is incapable of motion, and enclosed within the last larval skin, thus belonging to the coarctata Fig. 245.—Modth-parts ONE SIDE (from Hebt- wia). 7iy = hypopharynx, a process of labium. la = labium. Ir = labrum. md = mandible. mx = maxillae. p = maxillary palp. The larvae are. Please note that these images are extracted from scanned page images that may have been digitally enhan
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
