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578 HEMIPTERA-HOMOPTERA chap. 



quart vessel in an hour and a half. The frog-spit is considered 

 by some naturalists to be a protective device ; the larvae are, 

 however, a favourite food with certain Hymenoptera, which pick 

 out the larvae from the spits and carry them off to be used as 

 stores of provision for their larvae. In Ceylon the larva of 

 Mdchaerota guttigera constructs tubes fixed to the twigs of the 

 tulip-tree, and from the tube water is exuded drop by drop. 

 According to Westwood, this Insect is intermediate between 

 Cercopidae and Membracidae. 1 



Fam. 5. Jassidae.- — Ocelli two, placed just on the front 

 margin of the head (almost in a line with the front of the eyes 

 or more to the front) or on the dejicxed from. Hind tibiae 

 usual] I/ with many spines. This vaguely limited family includes 

 a very large number of small or minute Insects, usually of narrow, 

 parallel form, and frequently excessively delicate and fragile. 

 They are often mentioned under the name of Cicadellinae. 

 Ashmead distinguishes two families, Bythoscopidae, in which the 

 ocelli are clearly on the frons or front, and Jassidae, in which 

 they are on the upper edge thereof. * e> Ulopa,Ledra, and a few 

 other exceptional forms, are also by many distinguished as 

 representatives of distinct families. Very little is actually known 

 as to the life-histories of these small and fragile Insects, but it is 

 believed that the eggs are usually deposited in the leaves or 

 stems of plants, and more particularly of grasses. In North 

 America the development of-Deltocephcdus ini miens, from hatching 

 to assumption of the adult form, has been observed by Webster 

 to occupy about six weeks. As Jassidae are numerous both in 

 species and individuals it is believed that they consume a con- 

 siderable part of the vegetation of pastures. Osborn has 

 calculated that on an acre of pasture there exist, as a rule, about 

 one million of these hoppers, and he considers they obtain quite 

 as large a share of the food as the A'ertebrates feeding with 

 them. 



Fam. 6. Psyllidae. — Minute Insects with wings nsuedly 

 transparent, placed in a roof -like manner over the body; with three 

 ocelli, and rather long, thin antennae of eight to ten joints. Tarsi 

 two-jointed. — These small Insects have been studied chiefly in 

 Europe and North America, very little information having yet 

 been obtained as to the exotic forms. They are about the 

 1 Tr. ent. Soc. London, 1886, p. 329. 



