66 SOME SOUTH INDIAN INSECTS, ETC. [CHAP. VIII. 



such as those of Lichens and cattle-birds, in which the partners to 

 the arrangement do not feed on even the same class of food. Some 

 of the mites found so commonl) on the larger dung-beetles are 

 probably commensals rather than true parasites, helping to keep 

 their host clean by feeding on the particles of dung which get 

 attached to the short hairs, etc., on the body of the beetle. 



The small winged Borborid Hies {Limosina equitans) found 

 commonly clinging to the under-surface of the large dung-beetle 

 i S arabceits gangetu us) probablj feed on the same substances as the 

 beetle but are not symbiotic partners, as the beetle seems to derive 

 no benefit from the arrangement and merely provides transport tor 

 the flies, saving them the trouble of hunting for food for themseh es. 

 This i- an example ol what is called Phoresie. 



Social insects, also, although they feed on the same food, can 

 scarce! \ be called commensal-, because they do not belong to 

 different species and are therefore excluded by the definition of 

 symbiosis given above. 



Turning to a few examples of symbiotic relationships between 

 insects we find th.it social insects, as partners of the one part, 

 afford some of the best instances. Some caterpillars of the 

 Lycaenid (blue) butterflies possess on the posterior part of the back 

 a special gland from which they exude a sweet liquid greedily 

 sought after by various ants, which on their part tend and protect 

 the caterpillars; and these latter have become so dependent on the 

 attentions of the ant- that it is found impossible to rear them un- 

 less the ants are allowed access. Aphids (green-fly), Scale-insects, 

 and other plant-sucking bugs are also tended and protected in a 

 similar manner by ants who are repaid by the sweet honey-dew 

 which is exuded on their solicitation ; but in these case-, if ants are 

 not present or are in numbers insufficient to collect all the honey- 

 dew, this is voided excrementitioush by the Aphids, etc., whereas 

 the Lycaenid caterpillars do not seem able to get rid of their 

 secretion unless this i- removed by the ants. 



In the nests, also, ol both ants and Termites are found many 

 insects, belonging to almost all Orders, which are called myrmeco- 

 philous (ant-loving) or termitophilous (termite-loving), as the case 

 ma\ be, and which aw onlj found in these nests. Many of these 

 insects are truly parasitic on their hosts but many of them are 

 symbiotic partners. .Numerous small beetles, for example, found in 

 these nests are ted by their hosts and in return exude from special 

 glands a liquid which is eagerly sought after. In the case of some 

 root-feeding Aphids and Scale-insects, also, ant- are known to 

 cavate little chambers around roots on which they place these 

 insect- which are guarded and tended by the ants in exchange for 



