6 



numbers (save in exceptional seasons) b}^ natural enemies than the 

 melon aphis. The usefulness of these natural enemies, of which a 

 large number have been recorded, in subduing the aphides can not be 

 overestimated. Garden and field aphides generall}^ are subject to 

 attack by the same classes of parasitic and predaceous enemies. The 

 number of species of insects known to prey upon the melon aphis is 

 about 35. The list includes many ladybirds or " lad3^bugs " (Cocci- 

 nellidae)," which destroy the aphis both as beetles and as larvse; the 

 maggots of certain syrphus-flies (Syrphidse),^ which consume large 

 numbers of aphides; aphis lions — the larvae of lace-wing flies, of the 

 families Chrysopidse and Hemerobiid^e.^ A number of species of para- 

 sitic insects, chiefly minute forms of Braconidse, are also ver}^ impor- 

 tant checks on the increase of aphides.^^ Many, too, are destroj^ed by 

 parasitic fungi. 



The insect enemies of these, as of other aphides, keep their hosts, 

 in many portions of the country and in ordinary seasons, in nearly 

 complete subjection. The parasites, in particular, are most effective 

 in dr}^, warm weather. In cooler, moist summer weather, especiall}^ 

 following the same atmosvherlc conditions in spi'ing^ when vegetables 

 subject to aphis injury are starting growth, these otherwise natural 

 checks are less active, and the aphides, as a result, frequently gain the 

 ascendency. 



Some of the commonest species of ladybird enemies of this and 

 other aphides are illustrated in figure 3. In the ^' aphis j^ear" of 1898 

 the Scymnus (fig. 3, A, ^', j) was particularly abundant in and near the 

 District of Columbia on aphis-affected plants. ' A still more abundant 

 and useful form of this class of insects is the convergent ladybird 

 {Hipjjodamia convergens Guer.), shown in fig. 3, «, ^, c. It is fre- 



^Hippodamia convergens Guer. and Cydoneda sanguinea L. are prominent enemies, 

 as are also Megilla maculata De G. (fig. 3, d, e) and Cocdnella 9-)iotata Hbst. Other 

 species are Scymnus terminatus Say, S. caudalis Lee, S. cervicalis Muls. (A), 

 Chilocorus bivulnerus Muls., Exochomus constristatus Muls. (H), and Hippodamia 

 13-punctata L. 



^Syrphus flies include /S^rp/ms americanMs Wied., Allograpta obliqua Say, Baccha 

 clavata Fab. {babista Walk.), B. lugens Loew. (H), B. cognata Loew. (H), B. fusci- 

 pennis Say (A), and Eupeodes volucris 0. S. An agromyzid fly, Leucupis nigricornh 

 Egger, also preys on this aphis. Cecidomyiid enemies include certain undetermined 

 species of Contarinia (Diplosis). 



<^ Among the lace- wing flies are Chrysopa oculata Say, C. plorabunda Fitch, C. albi- 

 cornis Fitch (A), C. nigricornis Burm. (A), C. lineaticornis Fitch (A), C. attenuaia 

 Walk. (A), Micromus posticus Walk., and Hemerobius gossypii Ashm. (A). 



^ Parasitic braconids include Trioxys testaceipes Cress. , Lysiphlebus gossypii Ashm., 

 L. citraphis Ashm., L. cucurbitaphis Ashm., L. minidus Ashm., Lysiphlebus sp., and 

 Pachyneuron sp. A chalcis fly, Stenomesius aphidicola Ashm., has also been reared. 



The species followed by ( H) were observed attacking Aphis gossypii on orange trees 

 in Florida by H. G. Hubbard, those marked (A) by Wm. H. Ashmead on cotton in 

 Mississippi. The others are mostly well known, and have been observed by various 

 persons, as well as by the writer. 



