42 



THE AGKICULTURAL MEWS 



February 10, 1917. 



INSECT NOTES. 



THE VELVET BEAN CATERPILLAR. 



The larvae of the above noctuid moth is perhaps the 

 conimonest of the leaf-eating caterpillars attacking several 

 leguminous plants used generally throughout the West Indies 

 as green dressings, and it is probably distributed in most 

 places where these plants are grown. It has been reported 

 as attacking velvet beans iStizolobium sp.), lima beans 

 {Phaseolus liinatvs), woolly pyrol (Phaseolus mungo), Bengal 

 beans {Slirolobium alerrimum), horse beans (Cnnavalia 

 ensiforijiis) etc. and bears such common names as velvet bean 

 caterpillar, Bengal bean caterpillar, woolly pyrol moth, etc. 

 in different localities. Its scientific name is Anticarsia 

 {Thermeda) yenimatilis, Hubner. 



This insect is also an important enemy of forage and 

 green dressing legumes in Florida and Southern Georgia 

 where its life-history has been worked out by J. R. Watson, 

 and the details published in the Journal of Economic Entom- 

 ology (Vol. L\, p. •'v21), from which most of the following 

 notes are taken. 



Observations made by Watson within the last few 

 •seasons show that this noctuid does not pass the winter in 

 northern or central Florida, but flies up each year from the 

 south, and 'like the moth of the cotton worm (Alabama ay- 

 gillacea) migrates to regions far north of those in which its food 

 plants are found'. The annual flight of Anticarsia gemmatilu 

 takes it as far north as the lower part of the great Lakes and 

 southern New York. The caterpillars, on the other hand, 

 have apparently not been recorded farther north than central 

 Georgia, neither are they known in the western gulf states, 

 although their food plants are grown there. The moths first 

 appear in northern Florida around Gainesville about the 

 middle of August and the attack of the caterpillars comes 

 early in September during the blossoming period, often 

 causing a defoliation of the plants and a total loss of seed. 

 The stripping of the leaves lessens the value of the crop as 

 a humus producer, while the destruction of the pods and 

 seeds deprives stock of some ol their winter forage. 



LIFt-HISTOEY. 



The eggs are laid singly, mostly on the under side of 

 the leaves, but may be found elsewhere. 'The egg is nearly 

 2 mm. in diameter and somewhat less in height and flattened 

 on its lower surface. It is prominently ribbed and white 

 until about a day before hatching when it turns a delicate 

 pink.' In August and September it hatches in about three 

 days but those laid in November take longer. 



On emerging the larva first eats the egg shell except 

 that part attached to the leaf. After which it attacks the 

 lower epidermis and mesophyll or middle layers of leaf cells, 

 and then skeletonizes the leaf, eating all except the veins. 

 After the second instar the caterpillars demolish the whole 

 leaf except the midrib and larger veins. The larval growth 

 occupies from three to four weeks in summer, and there are 

 usually six instars. 



The caterpillars exhibit great variations in colour and 

 markings especially after the second in.star. They are 

 usually dark green with dark-coloured longitudinal lines and 

 narrower lines of lighter colour. Others may be light yellow- 

 ish-green, or mahogany brown with the lines very faint or 

 lacking. The length of the full grown larvae i.s from .38 to 

 4y mm. and before changing to the pupa it shrinks to about 

 25 mm and turns mahogany brown. 



The pupa is at first light green, but later becomes brown, 

 smooth and shining. It has a .somewhat pointed head and 

 three pairs of hooked spines ai. the end of the abdomen, one 



pair being much larger than the others. Length 18-20 mm., 

 width 4-6 mm. The pupae are usually placed just under the 

 surface of the soil, sometimes in loose earthern cells. The 

 pupal stage is about seven days in August and between ten 

 and eleven days in September, gradually lengthening with 

 the cooler weather to a month or more. 



The moth, like the caterpillar, is very variable. The 

 ground colour may be light yellowish brown, ashen gray or 

 dark reddish brown with a diagonal line across the wings. 

 The underside of the -wings is usually a cinnamon brown 

 with a sub-marginal row of light spots and a dark median 

 line. The adult moths are usually most active at dark, but 

 during the day they hide under the leaves of the host plants. 

 The caterpillars feed both day and night, stopping only to 

 moult. The younger caterpillars of the first and second instars, 

 if disturbed, drop down on a silken thread: the older larvae 

 however do not as a rule secrete this thread, but throw 

 themselves off the leaves by means of violent contortions. 

 The noise they make in so doing is quite characteristic and 

 serves to betray their presence to anyone walking through the 

 field. 



• NATtJRAL ENEMIES. 

 In Florida the caterpillars of the woolly pyrol moth are 

 attacked by many predaceous enemies, including lizards and 

 several kinds of birds. Among in.sects are some species of 

 wasps which prey upon the larvae, and a small blue carabid 

 beetle (Callida dfcora) which eats the eggs as well as the 

 young larvae. Several species of Hemiptera play an impor- 

 tant part in reducing the numbers of this pest, among which 

 are Alcororrhynchiis grandis, Dall., Brochymena annulata, Fab. 

 Earhyrhynchus floridensis, Linn, and Podisus nuiculiventris 

 Say. Ballon reports finding the predaceous hemipteron 

 Zfluf rubidus in Antigua associated with the caterpillars of 

 the woolly pyrol moth on cow peas, and regards it as a 

 predaceous enemy. Only two parasitic enemies were found 

 by Watson, namely a tachinid fly, Euphorocera. Horidensif 

 and an ichneumon wasp, Itoplectis rufuscula, Davis. 



MEASURES OF CONTROL. 



Towards the end of the summer, in September and 

 October, the caterpillars are regularly attacked by a disease 

 called 'choleia' by the farmers. This is caused by a fungus, 

 Botrutis rileyi, which under favourable weather conditions 

 almost exterminates the caterpillars in a short time and 

 saves the use of arsenical poisons. If, however, the season 

 is dry and unfavourable to the fungus, the crops are almost 

 wiped out by the caterpillars unless stomach poisons are 

 applied. In Florida the plants are sprayed with a mixture 

 • ontaining 12 oz. i>t powdered arsenate of lead, and the milk 

 from a pound of lime in -50 gallons of water. This is 

 apparently the maximum dose that the leaves will stand and 

 even then some scorching may result. 



It has been found from experiments made at this 

 Department by Ballou and from trials made in other islands 

 that it is not advisable to use Paris green to control cater- 

 pillars attacking the legumes, as this arsenical alway.s burns 

 the leaves badly if used at the strength necessary to kill the 

 caterpillars. Lead arsenate should be used instead. This 

 can be applied as a dust either by itself or mi,xed with flour 

 or lime, or may be used as a spray with water. These 

 measures are also i;c;oful against other leaf-eating caterpillars 

 attacking green dressings, such as the bean leaf-roller 

 (Eiidamui proteus). 



The practice nl early planting can be recommended, .so 

 that these crops raa\ be well advanced before the outbreak 

 of leaf-eating catirpillars becomes severe in August and 

 September, 



J.C.H, 



